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posted on 05 September 2017

September 4, 2017 Weather and Climate Report - NOAA Updates September Outlook

Written by Sig Silber

We anxiously await Irma (which, based on the current track, will impact Florida) as we digest the end of month Update by NOAA of the Early Outlook for the following month (in this case September) and it is a substantial change. Also of interest is the status of a possible La Nina. So there is much to discuss.


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Our continual update of IRMA can be accessed here. You can return to the Weekly Report by hitting your "Back Arrow", usually top left corner of your screen just to the left of the URL box. Irma will also be discussed in this weekly report (it is in the four-week period that we cover in this report) but the National Hurricane Track Forecasts and discussions are provided and updated in our special report on IRMA. We are then able to update those frequently.


A note on Harvey

September 4, 2017 Atmospheric Anomalies

This graphic is very difficult to read and interpret. The anomalies kind of blot out the geography. This graphic shows the upper atmosphere winds pretty much at the top of the Jet Stream and it you look closely you can see the wind direction and velocity and figure out where there is a ridge and where there is a trough. The text is probably the easiest way to make sense out of this. If you have a clockwise spinning High to the left of a counter-clockwise spinning Low (the referenced trough) it It is difficult for another system to intrude between the two of them from the south. Is this appropriately called Climate Change? I think not. Unless you can show either a pattern of this happening at the time there are such storms like Harvey in the GOM or can explain why it is more likely to happen due to Global Warming, it seems to me to be irresponsible to just hang a label on what appears to be a somewhat random event. It may not be random but that then requires an explanation.

NOAA Update of their Outlook for September

NOAA has, as usual, issued an update for the month following the last day of the prior month. This update was issued on August 31 and rather than have a Special Update that covers simply the next month, we combine that report with our Regular Weekly Report and we present the Updated Outlook and compare it to the Early Outlook for September issued on August 17, 2017. 

Temperature

Prior Outlook Issued on August 17, 2017

September Early Temperature Outlook Issued on August 17, 2017

Updated Outlook Issued on August 31, 2017

Temperature September, 2017 Outlook Updated on August 31, 2017

This is a substantial change in just fourteen days with the West and Alaska remaining warm but from CONUS west to east there is now a large cool anomaly and then EC except for a small part of New England and most of Florida which remain as being forecast to be warm. It is a big change in the size of the cool anomaly.

Precipitation

Prior Outlook Issued on August 17, 2017

September Precipitation Early Outlook Issued on August 17,  2017

Updated Precipitation Outlook Issued on August 31, 2017

September Precipitation Outlook Updated on August 31, 2017

This also is a large change with a dry anomaly in the North Central extending to the Northwest and a wet anomaly extending from Nevada to Colorado and a dry anomaly in Central Alaska. NOAA says that they suspected that this might be the correct forecast two weeks ago but they did not have sufficient confidence to have this be their Early Outlook.

30-DAY OUTLOOK DISCUSSION FOR SEPTEMBER 2017

THE BACKGROUND CLIMATE DRIVERS REMAIN UNCHANGED FROM THE 0.5-MONTH LEAD FORECAST. THE MJO HAS RECENTLY EMERGED OVER THE INDIAN OCEAN, BUT ITS FUTURE EVOLUTION IS UNCERTAIN. THE DEVELOPMENT OF HURRICANE IRMA IN THE ATLANTIC BASIN IS CONSISTENT WITH THE CURRENT MJO EVOLUTION, BUT BEYOND THAT THERE IS LITTLE TROPICAL VARIABILITY TO HARVEST FOR THE MONTHLY FORECAST AT THIS TIME.

THE UPDATED MONTHLY OUTLOOK MAINLY TAKES INTO ACCOUNT THE LATEST FORECASTS FOR THE NEXT ONE TO TWO WEEKS, WITH SOME MINOR INFLUENCE FROM THE LATEST WEEKS 3-4 GUIDANCE. THE FORECAST RIDGE/TROUGH PATTERN THAT WAS DISCUSSED FOR THE 0.5-MONTH LEAD FORECAST IS FORECAST TO BE ESPECIALLY AMPLIFIED DURING THE FIRST  5-10 DAYS OF THE MONTH, THOUGH SLIGHTLY FARTHER EAST THAN WAS FORECAST A COUPLE OF WEEKS AGO. THIS AMPLIFIED PATTERN DOMINATES THE UPDATED MONTHLY FORECAST, WITH SOME TENDENCY TOWARD THE LONG-TERM TREND MORE LIKELY LATE IN THE MONTH. THE IMPACT OF THIS ON THE MONTHLY FORECAST IS TO SHIFT AREAS OF PROBABILITIES EAST, WITH BELOW-NORMAL TEMPERATURES FAVORED OVER MUCH OF THE EAST-CENTRAL CONUS. PROBABILITIES FAVORING ABOVE-NORMAL TEMPERATURES OVER THE EAST COAST HAVE RETREATED FOR ALL BUT FAR EASTERN NEW ENGLAND AND THE FLORIDA PENINSULA.  PROBABILITIES FAVORING ABOVE-NORMAL TEMPERATURES OVER THE WESTERN CONUS HAVE BEEN ELEVATED, WITH VERY WARM TEMPERATURES NOW ANTICIPATED EARLY IN THE MONTH AND NO DISCERNIBLE SIGN OF A NOTABLE PATTERN CHANGE COMING LATER IN THE MONTH FROM ANY FORECAST TOOL. PARTS OF THE CENTRAL CONUS RETAIN A GOOD DEAL OF UNCERTAINTY, WITH A BACK-AND-FORTH PATTERN DURING THE FIRST TWO WEEKS OF THE MONTH EXPECTED TO LEAVE PARTS OF THAT REGION SITTING NEAR NORMAL. THE WEEK 3-4 FORECAST GUIDANCE DOES NOT INDICATE ANY STRONG SIGNALS FOR LATE MONTH OVER THE MIDWEST AND MOST OF THE PLAINS, FOR EXAMPLE, AND TRENDS FAVORING ABOVE-NORMAL TEMPERATURES ARE QUITE STRONG.

THE PRECIPITATION OUTLOOK IS BROADLY SIMILAR TO THE MID-MONTH OUTLOOK, BUT PROBABILITIES ARE ENHANCED OVER REGIONS EXPECTING HEAVY RAINFALL OVER THE NEXT SEVERAL DAYS. THIS INCLUDES AREAS AFFECTED BY THE REMNANTS OF HURRICANE HARVEY AT THE BEGINNING OF THE MONTH. IN ADDITION, ODDS FAVORING BELOW-NORMAL PRECIPITATION ARE ADDED OVER PARTS OF THE NORTHWEST AND PLAINS. THIS WAS DEBATED FOR THE MID-MONTH OUTLOOK, AND THE VARIOUS FORECAST TOOLS HAVE CONVERGED ON A FAIRLY CONFIDENT BELOW-NORMAL RAINFALL FORECAST CENTERED OVER THE NORTH-CENTRAL PLAINS. KEY AREAS OF UNCERTAINTY INCLUDE THE GULF COAST AND FLORIDA, AS WELL AS PARTS OF THE WEST.  THERE IS LIKELY TO BE SOME TROPICAL MOISTURE DIRECTED ALONG AN APPROACHING COLD FRONT EARLY IN THE MONTH OVER THE GULF COAST, AND THE LATEST GUIDANCE FROM THE ECMWF SUGGESTS THAT HURRICANE IRMA COULD IMPACT FLORIDA OR PARTS OF THE GULF COAST. OVER THE NORTHWEST, CLIMATOLOGICAL PRECIPITATION AMOUNTS BEGIN TO INCREASE DURING THE MONTH, WITH ONLY FAIRLY WEAK FORECAST SIGNALS PRESENT FOR THE SECOND HALF OF THE MONTH. PARTS OF THE GREAT BASIN AND CENTRAL ROCKIES ARE FORECAST TO SEE LOCALLY HEAVY RAINFALL EARLY IN THE MONTH, AND THE FORMER COULD BE IMPACTED BY A MOISTURE SURGE ASSOCIATED WITH TROPICAL STORM LIDIA IN THE EAST PACIFIC.

Sometimes it is useful to compare the present month outlook to the three-month outlook

September Plus September  -  November 2017 Outlook

September and SON 2017 Updated on August 31, 2017

One can mentally subtract the September Outlook from the three-month Outlook and create the Outlook for the last two months in the three-month period namely October and November,  2017. To  do that you need to take into account that:

Re temperature, the difference between September and the three-month map is very different for most of the eastern two thirds of CONUS especially from Texas northeast to the Mid-Atlantic states. Re precipitation, the spatial distribution of precipitation probabilities in Alaska has changed a bit but the major change is the North Central dry anomaly in September as well as the Nevada to Colorado wet anomaly and the rotation of the Southeast Anomaly in the three-month map to being and Eastern wet anomaly in September.
Thus if you assume these colors are assigned correctly, it is a simple algebra equation to solve October/November probability for a given location = (3XThree-Month Probability - September Probability)/2*. So you can derive the October/November forecast this way. You can do that calculation easily for where you live.

 

One has to keep in mind that we are now subtracting a September Map issued on August 31 from a three-month map issued on August 17. So it is less reliable than the exercise we went through in the special Update Report. We are assuming that the three-month outlook issued on August 17 would not change if it was updated on August 31. The results in the box above might be an indication of how October and November will differ from the three-month outlook or it might alternatively indicate how the three-month outlook might be modified if issued today. So the discussion in the paragraph above this may be overruled by a conclusion that the three-month outlook is no longer correct and the updated September Outlook is a better predictor of the three-month outlook than the three-month maps issued on August 17. 
 From the discussion released by NOAA on August 31,  the changes mentioned would appear not to extend to the Three-Month forecast so I would be inclined to look at these changes as being mostly apply only to the month of September. A reasonable conclusion then is that the previously issued Three-Month map is probably best thought of as being the map for October/November making the calculations described above not particularly useful.

 

 * The concept is that the probabilities of a deviation from climatology in the First Month and the combined Month Two and Three forecast that one derives must average out to the probabilities shown in the three-month maps.

We will now shift gears and resume our normal order of presentation: Forecast Summary with a Focus on the Southwest Monsoon

  Temperature Precipitation
 6 - 10 Day  6- 10 Day Temperature Forecast.  6 - 10 Day
 8 - 14 Day 6 - 14 Day Temperature Forecast  8 - 14 Day precipitation forecast

 

The above is what I am looking at Monday Night i.e. the NOAA forecast that is issued every day between 3pm and 4pm New York City time. It might be different if you do not read my report until after 3pm New York Time on Tuesday as the above maps will have updated and may look a little (and sometimes more than a little) different. The forecast can change and even if it does not change the dates that fit into the day 6 to 10 period and day 8 - 14 period change each day. So the forecast can remain the same but the maps showing a particular period of time will change and of course with weather it is not unusual for the forecast to change.

A. Focus on Alaska and CONUS (all U.S.. except Hawaii)

First Let us focus on the Current (Right Now to 5 Days Out) Weather Situation.

Water Vapor.

This view of the past 24 hours provides a lot of insight as to what is happening.

Eastern Pacific Animation

Below is the same graphic as above but without the animation to show the current situation with respect to water vapor imagery for North America. It also covers more of CONUS.

 Water Vapor Imagery

Tonight, Monday evening September 4, 2017, as I am looking at the above graphic, you can see a fairly peaceful situation with a cold wave sweeping across the Northeast.

Looking at the current activity of the Jet Stream.

Not all weather is controlled by the Jet Stream (which is a high altitude phenomenon) but it does play a major role in steering storm systems especially in the winter The sub-Jet Stream level intensity winds shown by the vectors in this graphic are also very important in understanding the impacts north and south of the Jet Stream which is the higher-speed part of the wind circulation and is shown in gray on this map. In some cases however a Low-Pressure System becomes separated or "cut off" from the Jet Stream. In that case it's movements may be more difficult to predict until that disturbance is again recaptured by the Jet Stream. This usually is more significant for the lower half of CONUS with the cutoff lows being further south than the Jet Stream. Some basic information on how to interpret the impact of jet streams on weather can be found here and here.

Current Jet Stream

One sees the current jet stream above. It is fairly far north.

This graphic provides a good indication of where the moisture is. It is a bit different than just moisture imagery as it is quantitative.

 Center for Western Weather and Water Extremes, Scripps/UCSD.

This graphic is about Atmospheric Rivers i.e. thick concentrated movements of water moisture. More explanation on Atmospheric Rivers can be found by clicking here or if you want more theoretical information by clicking here. The idea is that we have now concluded that moisture often moves via narrow but deep channels in the atmosphere (especially when the source of the moisture is over water) rather than being very spread out. This raises the potential for extreme precipitation events.
This evening we see Lidia hanging around near and over California. We also see an atmospheric river moving across the Northern Tier starting over the Great Lakes. That would seem to be connected to that cold wave.

You can convert the above graphic in to a flexible forecasting tool by clicking here.  One can obtain views of different geographical areas by clicking here

Day Two CONUS Forecast

Day 2 Forecast

60 Hour Forecast.Animation

Here is a national animation of weather fronts and precipitation forecasts with four 6-hour projections of the conditions that will apply covering the next 24 hours and a second day of two 12-hour projections the second of which is the forecast for 48 hours out and to the extent it applies for 12 hours, this animation is intended to provide coverage out to 60 hours. Beyond 60 hours, additional maps are available at links provided below.

current highs and lows

The explanation for the coding used in these maps, i.e. the full legend, can be found here although it includes some symbols that are no longer shown in the graphic because they are implemented by color coding.

Tropical Activity

Eastern Pacific Two Day Tropical Weather Outlook

When there is activity and I have not provided the specific links to the storm of "immediate" interest, one can obtain that information at this link.  At this point in time, no tropical events are expected to appear in this graphic during the next 48 hours. If that changes, we will provide an update. Obviously Irma is heading our way but is not within the boundaries of this graphic which is offset a bit to focus on the Pacific.

Below is a graphic which highlights the forecasted surface Highs and the Lows re air pressure on Day 6. The Day 3 forecast can be found here. I used to present the Day 3 with a link to Day 6 but showing Day 6 may be more useful.

Day 6 Weather Forecast

When I look at this Day 6 forecast, there is a large low over Alaska but impacting much of Canada having a surface central pressure of 1000 hPa. There is another low just east of Kamchatka with a surface low pressure of 1008 hPa.
The High Pressure off of the West Coast, the familiar RRR or more properly called the Eastern Pacific Semi-tropical High or the Hawaiian High, is reduced in size, partly on land, and has a surface central pressure of 1020 hPa. This configuration makes it likely that precipitation entering from the Pacific will do so in Canada rather than the Northwest. There also is a cut-off low shown south of Baja and a wave of some sort in the Gulf of California. And of course there is Irma with a central surface pressure of 988 hPa which may be an underestimate. Earlier this evening I saw a cold front to the Northwest of Irma but now it shows as more of a stationary front. Remember this is a Day 6 Forecast Map.
I provided this  K - 12 write up that provides a simple explanation on the importance of semipermanent Highs and Lows and another link that discussed possible changes in the patterns of these highs and lows which could be related to a Climate Shift (cycle) in the Pacific or Global Warming. Remember this is a forecast for Day 6. It is not the current situation.

Now looking at the Day 5 Jet Stream Forecast.

Jet Stream Five Days Out .

This is a Day 5 forecast by one model. You can see the Jet Stream is

Putting the Jet Stream into Motion and Looking Forward a Few Days Also

To see how the pattern is projected to evolve,  please click here. In addition to the shaded areas which show an interpretation of the Jet Stream, one can also see the wind vectors (arrows) at the 300 Mb level.

This longer animation shows how the jet stream is crossing the Pacific and when it reaches the U.S. West Coast is going every which way.

When we discuss the jet stream and for other reasons, we often discuss different layers of the atmosphere. These are expressed in terms of the atmospheric pressure above that layer. It is kind of counter-intuitive to me. The below table may help the reader translate air pressure to the usual altitude and temperature one might expect at that level of air pressure. It is just an approximation but useful.

air pressure and altitude
Re the above, H8 is a frequently used abbreviation for the height of the 850 millibar level (which is intended to represent the atmosphere above the Boundary Layer most impacted by surface conditions), H7 is the 700 mb level, H5 is the 500 mb level, H3 is the 300 mb level. So if you see those abbreviations in a weather forecast you will know what they are talking about.

Click here to gain access to a very flexible computer graphic. You can adjust what is being displayed by clicking on "earth" adjusting the parameters and then clicking again on "earth" to remove the menu. Right now it is set up to show the 500 hPa wind patterns which is the main way of looking at synoptic weather patterns. This amazing graphic covers North and South America. It could be included in the Worldwide weather forecast section of this report but it is useful here re understanding the wind circulation patterns.

You can enlarge the below daily (days 3 - 7) weather maps for CONUS by clicking on Day 3 or Day 4 or Day 5 or Day 6 or Day 7. These maps auto-update so whenever you click on them they will be forecast maps for the number of days in the future shown.

Short term forecasts

Here is the seven-day cumulative precipitation forecast. More information is available here.

Seven Day WPC Quantitative precipitation forecast

We see a high level of cumulative precipitation on and near Florida. We should expect that forecast to be refined often over the next few days and this graphic will auto-update.

The map below is the mid-atmosphere 7-Day chart rather than the surface highs and lows and weather features. In some cases it provides a clearer less confusing picture as it shows only the major pressure gradients. This graphic auto-updates so when you look at it you will see NOAA's latest thinking. The speed at which these troughs and ridges travel across the nation will determine the timing of weather impacts. This graphic auto-updates I think every six hours and it changes a lot. Because "Thickness Lines" are shown by those green lines on this graphic, it is a good place to define "Thickness" and its uses. The 540 Level general signifies equal chances for snow at sea level locations.Thickness of 600 or more suggests very intensely heat and fire danger.

7 Day 500 MB Geopotential Forecast

Thinking about clockwise movements around High Pressure Systems and counter- clockwise movements around Low Pressure Systems provides a lot of information.
What we see for Day 7 is Irma having moved through Florida into Georgia and South Carolina as I am looking at it and being further north by the time you look at it unless NOAA changes their ideas on the track. There is also a Low off the coast of California which would impact California and Arizona. The High over Arizona and New Mexico suggests that Monsoonal action will be limited there.
Remember this is a forecast for Day 7. Note the 540 Thickness Line re the above discussion of thickness and snow likelihood. Thickness lines near or over 600 tend to suggest very warm temperatures. Sometimes Meteorologists work with the 500 mb heights which provides somewhat similar readings to the "Thickness" lines but IMO provide slightly less specific information. The Southwest Heat Wave appears to potentially be ready to make a comeback as High Pressure and warm temperatures go together. Where the air pressure is highest often is an indication of where the warmest places will be.

Four- Week Outlook

I use "EC" in my discussions although NOAA sometimes uses "EC" (Equal Chances) and sometimes uses "N" (Normal) to pretty much indicate the same thing although "N" may be more definitive. 

First - Temperature

I am starting with a summary of small images of the three short-term maps. This summary provides a quick look. I could have made it so you could click and enlarge the small images but for the moment I prefer that you go past the summary for the larger versions because if I set up such links, the chances increase that you will not back out of the link properly and get lost. For most people the summary with the small images will be sufficient. Following the graphic with the three small images, you can find the larger maps and a discussion and for reference purposes I then also provide the forecast map for the current or soon to be current full month and the three-month forecast map. These are issued and updated less frequently than the first three maps shown.

Small Images of Temperature Maps
6 to 10 Days 8 to 14 Days Weeks 3 and 4
6 to 10 Day 8 - 14 Weeks 3 and 4
The above shows the progression of forecasts from six days out through four weeks out. Larger maps with discussion appear below. But this set of three maps paints a pretty good picture of what the forecast is.

 

Now the larger maps followed by a discussion that describes what is happening and any inconsistences that I see.

6 - 10 Day Temperature Outlook issued today (Note the NOAA Level of Confidence in the Forecast Released on September 4, 2017 was 3 out of 5)

6 - 10 Day Temperature Outlook

8 - 14 Day Temperature Outlook issued today (Note the NOAA Level of Confidence in the Forecast Released on September 4, 2017 was 2 out of 5).

 

8-14 Day Temperature Outlook

Looking further out.

Experimental Week 3-4 Temperature Outlook

Consolidation of 6 - 10, 8 - 14 and Experimental Week 3-4 Temperature Forecasts

Interpreted on September 4, 2017

September 10 to September 18 September 16 to September 29

Days 6 - 10: Alaska is cool and the Panhandle is warm. The western half of CONUS plus the extreme northern part of New England is warm. A  cool anomaly is centered just east of the Lower Mississippi and extends west into Texas and east and northeast into the Mid-Atlantic States.

For CONUS, The West except for the extreme Southwest is warm.There is a cool swath starting in Mississippi and trending NE to Cape Hatteras. In between the warm and cool areas is a lot of EC. Alaska is warm  to the Northeast with a cool center.

The transition to the pattern shown in the Week 3 - 4 Forecast from the pattern shown in the 8-14 Day forecast appears to be feasible if the west to east normal progression of weather ceases.

Week 2:  As the period evolves the cool anomaly moderates. The Florida warm anomaly grows. The Alaska cool anomaly becomes less dominant.

Remember the Week 3-4 Experimental Outlook was issued last Friday and I am looking at the 6 - 10 and 8 - 14 day forecasts issued today i.e. Monday. So that explains the overlap of dates. Remember that the Week 3 - 4 Forecast covers two weeks so it can appear to not mesh perfectly but actually do so over the two-week period. For all three time periods, in between the cool and warm anomalies it is usually EC i.e. the boundary is usually not sharp.

 

Reference Forecasts Full Month and Three Months.

Below is the Temperature Outlook for the month shown in the Legend. This map is first issued on the Third Thursday of the Month for the following month and then updated on the last day of the month. The 6 - 10 day and 8 - 14 Day update daily and the Week 3/4 Map Updates every Friday so usually these are more up-to-date.  Note that the three maps shown at the beginning of this discussion on temperature may cover a slightly different time period since they update as the month progresses and the map below covers a particular month shown in the Legend. It is useful if one wants to understand how that month is forecast to play out.

September Temperature Outlook Updated on August 31, 2017

Here is the Temperature Outlook issued on the date and for the three-month period shown in the Map Legend. Again this is provided for reference only. It is the same map that is included in our Saturday night report that follows the NOAA third Thursday of the month Seasonal Outlook Update. It provides a longer time frame than the above maps. It uses a totally different methodology as it is not possible to use the dynamical models to project out three months. The dynamical models work by figuring out how the current conditions will evolve over a fairly short period of time. To look out three months or longer the approach is more statistical using the forecasted ENSO Phase and Climate Trends.

The theory behind using dynamical models for short-term forecasts (6  10 Days, 8 - 14 Days, and recently Weeks 3-4) and statistical models (Monthly and Three-Months) for longer-term forecasts makes perfect sense but sometimes we see that the short term forecasts and then the actuals do not match the statistical forecasts very well. This tells us that either the statistical forecasts were based on incorrect assumptions or that the actual weather patterns are different from what we might have expected.

SON 2017 Temperature Outlook Issued on August 17, 2017

Now - Precipitation

I am starting with a summary of small images of the three short-term maps. This summary provides a quick look. I could have made it so you could click and enlarge the small images but for the moment I prefer that you go past the summary for the larger versions because if I set up such links, the chances increase that you will not back out of the link properly and get lost. For most people, the summary with the small images will be sufficient. Following the graphic with the three small images, you can find the larger maps and a discussion and for reference purposes I then also provide the forecast map for the current or soon to be current full month and the three-month forecast map. These are issued and updated less frequently than the first three maps shown.

Small Images of Precipitation Maps
6 to 10 Day 8 to 14 Day Weeks 3 and 4
6 to 10 Day 8 - 14 Weeks 3 and 4
The above shows the progression of forecasts from six days out through four weeks out. Larger maps with discussion appear below. But this set of three maps paints a pretty good picture of what the forecast is.

 

Now the larger maps followed by a discussion that describes what is happening and any inconsistencies that I see.

6 - 10 Day Precipitation Outlook Issued Today (Note the NOAA Level of Confidence in the Forecast Released on September 4 was 4 out of 5)

6 - 10 Day Precipitation Outlook

8 - 14 Day Precipitation Outlook Issued Today (Note the NOAA Level of Confidence in the Forecast Released on September 4, 2017 was 2 out of 5)

Current 8 - 14 Day Precipitation Outlook

Looking further out.

Weeks 3 and 4 Experimental Forecast..

Consolidation of 6 - 10, 8 - 14, and Week 3-4 Precipitation Forecasts

Interpreted on September 4, 2017

September 10 to September 18  September 16 to September 29, 2017

Days 6 -10: CONUS Northwest is dry. To the southeast of the dry anomaly there is a wet anomaly centered over Utah. The central third of CONUS is dry, the Southeast is wet. Alaska East and the  Panhandle is wet with the west Normal and the Aleutians dry.

For CONUS, Utah and parts of neighboring states are wet. The Central Third of CONUS is dry. Alaska is dry.

The transition to the pattern shown in the Week 3 - 4 Forecast appears to be feasible if the west to east normal progression of weather ceases.

Week 2: As the period evolves, The Southwest wet anomaly travels north. In Alaska, the Panhandle becomes dry.

Remember the Week 3-4 Experimental Outlook was issued last Friday and I am looking at the 6 - 10 and 8 - 14 day forecasts issued today i.e. Monday. So that explains the overlap of dates. Remember that the Week 3 - 4 Forecast covers two weeks so it can appear to not mesh perfectly but actually do so over the two-week period. In between the dry and wet anomalies, it is usually EC i.e. the boundary is usually not sharp.

 

Reference Forecasts Full Month and Three Months.

Below is the Precipitation Outlook for the month shown in the Legend. This map is first issued on the Third Thursday of the Month for the following month and then updated on the last day of the month. The 6 - 10 day and 8 - 14 Day update daily and the Week 3/4 Map Updates every Friday so usually these are more up to date. Note that the three maps shown at the beginning of this discussion about precipitation may cover a slightly different time period since they update as the month progresses and the map below covers a particular month shown in the Legend. It is useful if one wants to understand how that month is forecast to play out.

September 2017 Precipitation Outlook Updated on August 31, 2017

Below is the Precipitation Outlook issued on the date and for the three-month period shown in the Map Legend. Again, this is provided for reference only. It is the same map that is included in our Saturday night report that follows the NOAA third Thursday of the month Seasonal Outlook Update. It provides a longer time frame than the above maps. It uses a totally different methodology as it is not possible to use the dynamical models to project out three months. The dynamical models work by figuring out how the current conditions will evolve over a fairly short period of time. To look out three months or longer, the approach is more statistical using the forecasted ENSO Phase and Climate Trends.

The theory behind using dynamical models for short-term forecasts (6 - 10 Days, 8 - 14 Days and recently Weeks 3-4) and statistical models for longer-term forecasts (Month and three months) makes perfect sense but sometimes we see that the short-term forecasts and then the actuals do not match the statistical forecasts very well. This tells us that either the statistical forecasts were based on incorrect assumptions or that the actual weather patterns are different from what we might have expected.

SON 2017 Precipitation Outlook Issued on August 20, 2017

Here is the NOAA discussion released today September 4, 2017

6-10 DAY OUTLOOK FOR SEP 10 - 14 2017

TODAY'S MODELS ARE IN FAIRLY GOOD AGREEMENT ON THE PREDICTED MID-TROPOSPHERIC CIRCULATION PATTERN OVER THE FORECAST DOMAIN. RIDGE ARE EXPECTED OVER THE WEST-CENTRAL CONUS EXTENDING NORTHEASTWARD TOWARDS THE GREAT LAKES, AND OVER THE EASTERN BAHAMAS/WESTERN ATLANTIC, WHILE TROUGHS ARE ANTICIPATED OVER THE EASTERN CONUS AND ALASKA. A WEAK TROUGH IS ANTICIPATED OVER THE WESTERN CONUS, ALTHOUGH HEIGHTS ARE FORECAST TO BE ABOVE NORMAL. UNCERTAINTY EXISTS IN REGARD TO THE INTERACTION OF THE TROUGH FORECAST OVER THE EASTERN CONUS AND HURRICANE IRMA. THIS UNCERTAINTY IS REFLECTED IN THE ENSEMBLE SPAGHETTI CHARTS WHICH GENERALLY INDICATE MODERATE TO LARGE SPREAD OVER MOST OF THE FORECAST DOMAIN, WITH LARGE SPREAD SHOWN IN REGARD TO THE EXPECTED AMPLITUDE OF THE TROUGH PREDICTED OVER THE EASTERN CONUS. TODAY'S 500-HPA HEIGHT BLEND CHART DEPICTS NEAR TO BELOW NORMAL HEIGHTS OVER MUCH OF THE SOUTHEASTERN CONUS AND ALASKA, WHILE NEAR TO ABOVE NORMAL HEIGHTS ARE FORECAST ACROSS THE REMAINDER OF CONUS AND THE ALEUTIANS. THE GREATEST WEIGHT FOR THE BLENDED HEIGHT FORECAST WAS GIVEN TO TODAY'S 00Z ECMWF ENSEMBLE MEAN, BASED ON CONSIDERATIONS OF RECENT SKILL.

BELOW NORMAL HEIGHTS TILT THE ODDS TO BELOW NORMAL TEMPERATURES FROM CENTRAL AND EASTERN TEXAS EAST-NORTHEASTWARD TO PARTS OF THE LOWER AND MIDDLE MISSISSIPPI VALLEYS, TENNESSEE AND OHIO VALLEYS, SOUTHEAST, SOUTHERN AND CENTRAL APPALACHIANS, AND MID-ATLANTIC. THE RIDGE NEAR THE BAHAMAS AND ABOVE NORMAL SEA-SURFACE TEMPERATURES FAVORS ABOVE NORMAL TEMPERATURES FOR SOUTHERN FLORIDA. NEAR TO ABOVE NORMAL HEIGHTS ENHANCE PROBABILITIES FOR NEAR TO ABOVE NORMAL TEMPERATURES FOR THE REMAINDER OF THE CONUS. BELOW NORMAL HEIGHTS TILT THE ODDS TO BELOW NORMAL TEMPERATURES FOR MAINLAND ALASKA, WHILE ABOVE NORMAL HEIGHTS FAVOR ABOVE NORMAL TEMPERATURES FOR PARTS OF THE ALEUTIANS.

THE PRECIPITATION FORECAST FOR THE EASTERN U.S. IS LARGELY DEPENDENT ON THE FUTURE TRACK OF HURRICANE IRMA AND ITS INTERACTION WITH THE TROUGH FORECAST OVER THE EASTERN CONUS. THE LATEST GUIDANCE FROM THE NATIONAL HURRICANE CENTER INDICATES THAT IRMA WILL TRACK CLOSE TO CUBA AND SOUTHERN FLORIDA. PROBABILITIES FOR ABOVE NORMAL PRECIPITATION ARE ENHANCED OVER MUCH OF THE EASTERN CONUS FROM FLORIDA TO SOUTHERN NEW ENGLAND. ABOVE NORMAL HEIGHTS TILT THE ODDS TO BELOW NORMAL PRECIPITATION FOR PARTS OF MAINE. ABOVE NORMAL HEIGHTS AND/OR ANOMALOUS NORTH/NORTHEASTERLY FLOW ENHANCES PROBABILITIES FOR BELOW NORMAL NORMAL PRECIPITATION FOR MUCH OF THE CENTRAL CONUS. THE WEAK TROUGH FORECAST OVER THE WESTERN U.S. FAVORS ABOVE NORMAL PRECIPITATION FOR PARTS OF THE CENTRAL GREAT BASIN AND SOUTHWEST. ABOVE NORMAL HEIGHTS TILT THE ODDS TO BELOW NORMAL PRECIPITATION FOR PARTS OF THE PACIFIC NORTHWEST AND THE NORTHERN INTERMOUNTAIN WEST. THE TROUGH FORECAST OVER MAINLAND ALASKA FAVORS ABOVE NORMAL PRECIPITATION FOR MUCH OF MAINLAND ALASKA AND THE ALASKA PANHANDLE, ALTHOUGH ABOVE NORMAL HEIGHTS AND ANOMALOUS NORTHWESTERLY FLOW ENHANCES PROBABILITIES FOR BELOW NORMAL PRECIPITATION FOR PARTS OF THE ALEUTIANS AND SOUTHWESTERN MAINLAND ALASKA.

­FORECAST CONFIDENCE FOR THE 6-10 DAY PERIOD: ABOUT AVERAGE, 3 OUT OF 5, DUE TO GOOD MODEL AGREEMENT ON THE EXPECTED FLOW PATTERN OVER MUCH OF THE FORECAST DOMAIN, OFFSET BY UNCERTAINTIES ASSOCIATED WITH THE FUTURE TRACK OF HURRICANE IRMA.

8-14 DAY OUTLOOK FOR SEP 12 - 18 2017 

COMPARED TO THE 6-10 DAY PERIOD, ENSEMBLE MEAN SOLUTIONS FORECAST A LESS AMPLIFIED PATTERN DURING WEEK-2. TROUGHS ARE EXPECTED TO PERSIST OVER THE EASTERN AND WESTERN CONUS, AND ALASKA, WHILE RIDGES ARE MAINTAINED OVER THE WEST-CENTRAL CONUS AND THE WESTERN ATLANTIC. THE ENSEMBLE SPAGHETTI CHARTS CONTINUE TO SHOW MODERATE TO LARGE SPREAD ACROSS MOST OF THE FORECAST DOMAIN. THE EXPECTED HEIGHT ANOMALY PATTERN FOR WEEK-2 IS QUITE SIMILAR TO THAT PREDICTED FOR THE 6-10 DAY PERIOD, ALTHOUGH HEIGHTS ARE FORECAST TO RISE OVER SOUTHWESTERN MAINLAND ALASKA DURING WEEK-2. 

THE RESULTING TEMPERATURE OUTLOOK IS VERY SIMILAR TO THAT FORECAST FOR THE 6-10 DAY PERIOD. PREDICTED RIDGING AND ABOVE NORMAL HEIGHTS ELEVATE CHANCES FOR ABOVE NORMAL TEMPERATURES FOR THE WESTERN, NORTH-CENTRAL AND NORTHEASTERN CONUS. BELOW NORMAL HEIGHTS AND/OR ANOMALOUS NORTHWESTERLY FLOW TILT THE ODDS TO BELOW NORMAL TEMPERATURES FOR MUCH OF MAINLAND ALASKA, WHILE ABOVE NORMAL HEIGHTS FAVOR ABOVE NORMAL TEMPERATURES FOR PARTS OF THE ALEUTIANS. A PREDICTED TROUGH AND BELOW NORMAL HEIGHTS ENHANCE THE ODDS FOR NEAR TO BELOW NORMAL TEMPERATURES FOR MUCH OF THE SOUTHEASTERN AND SOUTH-CENTRAL CONUS, EXCEPT FOR SOUTHERN FLORIDA WHERE NEAR TO ABOVE NORMAL TEMPERATURES ARE FAVORED. 

PREDICTED PRECIPITATION ANOMALIES FOR THE WEEK-2 PERIOD FOR THE EASTERN CONUS ARE OF LOW CONFIDENCE DUE TO LARGE UNCERTAINTY REGARDING THE FUTURE TRACK OF HURRICANE IRMA. THE TROUGH EXPECTED OVER THE EASTERN CONUS TILTS THE ODDS TO ABOVE NORMAL PRECIPITATION FOR PARTS OF THE SOUTHEAST, MID-ATLANTIC, NORTHEAST, OHIO AND TENNESSEE VALLEYS, AND THE APPALACHIANS. DESCENT ON THE REAR SIDE OF THE TROUGH, AND/OR ANOMALOUS NORTHEASTERLY FLOW FAVORS BELOW NORMAL PRECIPITATION FOR MUCH OF THE CENTRAL CONUS AND PARTS OF MAINE. THE WEAK TROUGH OVER THE WESTERN CONUS ENHANCES PROBABILITIES FOR ABOVE NORMAL PRECIPITATION FOR PARTS OF THE NORTHERN INTERMOUNTAIN WEST, CENTRAL GREAT BASIN, AND NORTHERN AND CENTRAL ROCKIES. ABOVE NORMAL HEIGHTS TILT THE ODDS TO BELOW NORMAL PRECIPITATION FOR PARTS OF THE NORTHWEST CONUS, SOUTHWESTERN MAINLAND ALASKA, AND THE ALEUTIANS. THE TROUGH OVER ALASKA FAVORS ABOVE NORMAL PRECIPITATION FOR MUCH OF CENTRAL AND NORTHERN MAINLAND ALASKA. 

FORECAST CONFIDENCE FOR THE 8-14 DAY PERIOD IS: BELOW AVERAGE, 2 OUT OF 5, DUE TO GENERALLY GOOD MODEL AGREEMENT OFFSET BY LARGE MODEL UNCERTAINTY ASSOCIATED WITH THE TRACK OF HURRICANE IRMA.

THE NEXT SET OF LONG-LEAD MONTHLY AND SEASONAL OUTLOOKS WILL BE RELEASED ON SEPTEMBER 21

Some might find this analysis which you need to click to read interesting as the organization which prepares it focuses on the Pacific Ocean and looks at things from a very detailed perspective and their analysis provides a lot of information on the history and evolution of ENSO events.

Analogs to the Outlook.

Now let us take a detailed look at the "Analogs" which NOAA provides related to the 5 day period centered on 3 days ago and the 7 day period centered on 4 days ago. "Analog" means that the weather pattern then resembles the recent weather pattern and was used in some way to predict the 6 - 14 day Outlook.

Here are today's analogs in chronological order although this information is also available with the analog dates listed by the level of correlation. I find the chronological order easier for me to work with. There is a second set of analogs associated with the Outlook but I have not been regularly analyzing this second set of information. The first set which is what I am using today applies to the 5 and 7 day observed pattern prior to today. The second set, which I am not using, relates to the correlation of the forecasted outlook 6 - 10 days out with similar patterns that have occurred in the past during the dates covered by the 6 - 10 Day Outlook. The second set of analogs may also be useful information but they put the first set of analogs in the discussion with the second set available by a link so I am assuming that the first set of analogs is the most meaningful and I find it so.

Centered

Day

ENSO

Phase

PDO AMO

Other Comments

Sep 1, 1955 La Nina - +  
Sep 8, 1981 Neutral + -  
Aug 24, 1988 La Nina +(t) +(t)  
Aug 29, 1988 La Nina +(t) +(t)  
Sep 1, 1988 La Nina -(t) +  
Aug 30, 1998 La Nina - + Following the MegaNino
Aug 31, 1998 La Nina - + Following the MegaNino

 

(t) = a month where the Ocean Cycle Index has just changed or does change the following month.

Two things jumped out at me right away. There were a lot of duplicate anomalies which I ignore but which is not quite right for determining the McCabe Condition that applies. Also the spread among the analogs from August 24 to Sept 8 which is only 15 days which is a much tighter spread in dates than recently. I have not calculated the centroid of this distribution which would be the better way to look at things but the midpoint, which is a lot easier to calculate, is about September 1. These analogs are centered on 3 days and 4 days ago (August 31 or September 1). So the analogs could be considered to be in sync with the calendar meaning that we will be getting weather that we would normally be getting right now. For more information on Analogs see discussion in the GEI Weather Page Glossary.

There are zero ENSO El Nino analogs (finally), one Neutral Analog (two if we count duplicates)  and six (eight if we count duplicates)  La Nina analogs. The phases of the ocean cycles of the analogs are most consistent with McCabe D and least consistent with McCabe B. Being least consistent with McCabe B reinforces the consistency with McCabe D since B and D are opposites. This leads me to suspect that the Northwest might end up being wetter than forecast in the NOAA 6 to 14 Day Outlook but it may be that this wetness is further north in Canada. Also the McCabe Conditions do not tell us much about the Atlantic tropical situation. It actually does tell us about the propensity for Hurricanes and where they might track but it does not tell us much about the short term re tropical storm activity.

The seminal work on the impact of the PDO and AMO on U.S. climate can be found here. Water Planners might usefully pay attention to the low-frequency cycles such as the AMO and the PDO as the media tends to focus on the current and short-term forecasts to the exclusion of what we can reasonably anticipate over multi-decadal periods of time. One of the major reasons that I write this weather and climate column is to encourage a more long-term and World view of weather.

McCabe Maps modified to include the subtitles

Sometimes it is easier to work in black and white especially if you print this report so there is a black and white version from the later report by the same authors. Darker corresponds to red in the color graphic i.e. higher probability of drought.

McCabe Conditions from 2007 report with labels corrected with authors permission

McCabe Condition Main Characteristics
A Very Little Drought. Southern Tier and Northern Tier from Dakotas East Wet. Some drought on East Coast.
B More wet than dry but Great Plains and Northeast are dry.
C Northern Tier and Mid-Atlantic Drought
D Southwest Drought extending to the North and also the Great Lakes. This is the most drought-prone combination of Ocean Phases.

 

You may have to squint but the drought probabilities are shown on the map and also indicated by the color coding with shades of red indicating higher than 25% of the years are drought years (25% or less of average precipitation for that area) and shades of blue indicating less than 25% of the years are drought years. Thus drought is defined as the condition that occurs 25% of the time and this ties in nicely with each of the four pairs of two phases of the AMO and PDO.

Looking Out Beyond Three Months

The Seasonal Outlook Update Report was issued in two parts because JAMSTEC was late. Part I which focused on the NOAA forecast comparing the new forecast to the prior forecast can be accessed here and Part II which focused on the comparison between the NOAA forecast and the JAMSTEC forecast can be accessed here. The Part II report was also used to provide updates on Harvey because I can only publish two reports at the same time and be able to update them. Remember, if you leave this page to visit links provided in this article, you can return by hitting your "Back Arrow", usually top left corner of your screen just to the left of the URL box. There will be a new Seasonal Outlook issued by NOAA on September 21 which we will report on September 23.

Historical Anomaly Analysis

When I see the same dates showing up often I find it interesting to consult this list.

Recent CONUS Weather

This is provided mainly to see the pattern in the weather that has occurred recently.

Here is the 30 Days ending August 26, 2017

August 26, 2017 30 Day Temperature and Precipitation Departures

You can see a little bit of the pattern shift east. It will be a lot clearer in a week. Remember, this is a 30 average so the most distant seven days are removed and the most recent seven days are added.

And the 30 Days ending September 2, 2017

September 2, 2017 30 Day Temperature and Precipitation Departures

You can clearly see the impact of Harvey. Otherwise there is very little change. Remember, this is a 30 average so the most distant seven days are removed and the most recent seven days are added.

B. Beyond Alaska and CONUS Let's Look at the World which of Course also includes Alaska and CONUS

Same as above but for July

I will be including the above two graphics regularly as they really help with understanding why things are happening the way they are. I think the (at least intermediate) Source is The Weather Channel and I was able to download the full presentation with difficulty and you can attempt the same thing by clicking here.
I think these two slides are from a much larger set but these two really highlight the position of the Bermuda High which they are calling the Azores High in the January slide and is often called NASH and it has a very big impact on CONUS Southeast weather and also the Southwest. You also see the north/south migration of the Pacific High which also has many names and which is extremely important for CONUS weather and it also shows the change of location of the ITCZ which I think is key to understanding the Indian Monsoon. A lot of things become much clearer when you understand these semi-permanent features some of which have cycles within the year, longer period cycles and may be impacted by Global Warming.
We are now approaching September so we are 1/3 between the set of positions shown above for July and the ones shown for January. For CONUS, the seasonal repositioning of the Bermuda High and the Pacific High are very significant. Notice the Summer position of the Pacific High.

Forecast for Today

Temperature at 2 Meters

Notice that below the map there is a tabulation of magnitude of the current anomalies by region. From North Africa to Eastern Siberia it is warmer than climatology except for Northeast China and Eastern Siberia and the Northern Tier which is Normal. CONUS Central is cool.

Maine Reanalyer

This graphic is actuals not anomalies as is the case in the temperature map. We again see the dry area from North Africa through Asia (other than Southeast Asia) but it is not extending all the way to the Pacific. South America south of the ITCZ is mostly dry. Africa north and south of the Equator and the ITCZ is mostly dry. And CONUS is mostly dry in the West. From Texas east it is a different story.

Additional Maps

showing different weather variables can be found here.

Forecast  for Day 6 (Currently Set for Day 6 but the reader can change that)

World Weather Forecast produced by the Australian Bureau of Meteorology. Unfortunately I do not know how to extract the control panel and embed it into my report so that you could use the tool within my report. But if you visit it Click Here  and you will be able to use the tool to view temperature or many other things for THE WORLD. It can forecast out for a week. Pretty cool. Return to this report by using the "Back Arrow" usually found top left corner of your screen to the left of the URL Box. It may require hitting it a few times depending on how deep you are into the BOM tool. Below are the current worldwide precipitation and temperature forecasts for six days out. They will auto-update and be current for Day 6 whenever you view them. If you want the forecast for a different day Click Here

Temperature

BOM Current Temperature Wedensday

Please remember this graphic updates every six hours so the diurnal pattern can confuse the reader.

Precipitation

BOM World Preciptation  Wednesday

Notice that in the Day 6 Forecast,  the Bermuda High also called NASH looks different as core is shifted to the east but if you look at all the contour lines ir remains extended way to the west. It retreated and allowed Harvey in but may be closing that window. NOAA thinks the window will open to allow Irma to proceed north.

Looking Out a Few Months

Here is the precipitation forecast from Queensland Australia:

Consistently Positive SOI  forecast for September to Novermber 2017.

It is kind of amazing that you can make a worldwide forecast based on just one parameter the SOI and changes in the SOI. Notice the change from the forecast last month due to a rising SOI to a consistently positive SOI. CONUS looks pretty dry except for the Northwest, Europe pretty wet. India wet, Australia wet, much of China wet.

JAMSTEC Forecasts

One can always find the latest JAMSTEC maps by clicking this link. You will find additional maps that I do not general cover in my monthly Update Report. Remember if you leave this page to visit links provided in this article, you can return by hitting your "Back Arrow", usually top left corner of your screen just to the left of the URL box.

Sea Surface Temperature (SST) Departures from Normal for this Time of the Year i.e. Anomalies

My focus here is sea surface temperature anomalies as they are one of the two largest factors determining weather around the World.

And when we look at the current Sea Surface anomalies below, we see a lot of them not just along the Equator related to ENSO.[NOAA may be having problems updating their daily SST Anomaly Report so I am working with the latest version that I have]

Daily SST Anomalies

First the categorization of the anomalies.

Mediterranean, Black Sea and Caspian Sea Western Pacific West of North America East of North America North Atlantic
The Caspian Sea and Persian Gulf are very warm with the Black Sea and Mediterranean only slightly warm.

Warm.

Fairly Neutral.

Warm out to sea and very spotty cool anomaly closer to shore and now also beyond the warm areas to barely create a visible PDO Signal. .

Fairly Neutral

Hudson Bay warm

Gulf of St Lawrence slightly Warm

Warm
The Equatorial

Cool east of Dateline.  Very cool southwest of Maritime Continent.

Africa West of Australia North, South and East of Australia

West of South America

East of South America

Slightly warm west of North Africa and Equator. Mixed off of South Africa

Cool northwest, west and southwest Cool to the south and slightly warm east. Cool mostly in conjunction to the ENSO Cycle. Also cool off shore at 40S to 50S Slightly warm 30S to 50S. Cool offshore of 20S

 

What you see in the below graphic is the change in the anomaly over the last four weeks So you have to refer to the graphic above this one to really interpret the below graphic as what we are seeing here is the change in the anomalies. So blue means a trend that is either cooler or less warm than four weeks ago. Red means a trend that is warmer or less cool than four weeks ago. So this graphic is a way of understanding how the anomalies shown in the above graphic have changed over the past four weeks. It is important to understand the distinction between these two graphics. The top one shows the recent conditions, the bottom one shows the direction of change.

September 4, 2017 four week change is SST Anomalies

The categorization of the four week change in the anomalies.

Mediterranean, Black Sea and Caspian Sea Western North Pacific West of North America East of North America North Atlantic

Fairly stable i.e. the anomalies are not changing much.

Mix of warming and cooling.

Waters around Japan are cooling

Cooling in the Bering Straits. and south of the Aleutians.

Warming west of CONUS off shore. Cooling for Baja California and in Gulf of California

Cooling off of Nova Scotia

Cooling in part of the Gulf of Mexico

Warming in Hudson Bay

Warming south of 40S near Greenland
The Tropical Pacific Eastern Pacific Cooling East of 150W.
Africa West of Australia North, South and East of Australia West of South America East of South America
Warming west of North Africa and the Equator west of Africa. Cooling south of Africa

Cooling to the west but off shore

Cooling to the east and south.

Stable

Mostly stable

 

It is very interesting that the entire North Pacific is showing Neutral or warm anomalies but when you look at the changes in the anomalies one gets a very different picture with many areas that are cooling (from their current temperature which is warmer than climatology).

This may be a good time to show the recent values to the indices most commonly used to describe the overall spacial pattern of temperatures in the (Northern Hemisphere) Pacific and the (Northern Hemisphere) Atlantic and the Dipole Pattern in the Indian Ocean.

Most Recent Six Months of Index Values PDO Click for full list

AMO click for full list.

Indian Ocean Dipole (Values read off graph)
October -0.68 +0.39 -0.3
November +0.84 +0.40  0.0
December +0.55 +0.34 -0.1
January +0.10 +0.23  0.0
February +0.04 +0.23 +0.2
March +0.12 +0.17 +0.0
April +0.52 +0.29 +0.2
May +0.30 +0.32 +0.2
June +0.19 +0.31  0.0
July -0.41 +0.31  0.0
August      

 

Switching gears, below is an analysis of projected tropical hazards and benefits over an approximately two-week period.

Tropical Hazards

This graphic updates on Tuesdays and I post on Monday which is almost a week later than when this graphic was last updated. So Week Two applies at the time I write this article on Monday but by the time you read it on Tuesday, the Week Two that I am looking at is updated and becomes Week One. Mostly I see as I look at this on September 4 for what is shown as Week Two, the period September 6 to September 12, 2017, we see wet conditions* over the northern part of the Maritime Continent and also Panama with dry conditions* in between India and Indochina. .
* Moderate Confidence that the indicated anomaly will be in the upper or lower third of the historical range as indicated in the Legend. 
** High Confidence that the indicated anomaly will be in the upper or lower third of the historical range as indicated in the Legend.

Now let us look at the Western Pacific in Motion.

Western Pacific Tropical Activity

The above graphic which I believe covers the area from the Dateline west to 100E and from the Equator north to 45N normally shows the movement of tropical storms towards Asia in the lower latitudes (Trade Winds) and the return of storms towards CONUS in the mid-latitudes (Prevailing Westerlies). This is recent data not a forecast. But, it ties in with the Week 1 forecast in the graphic just above this graphic. Information on Western Pacific storms can be found by clicking here. This (click here to read) is an unofficial private source but one that is easy to read.

C. Progress of ENSO

A major driver of weather is Surface Ocean Temperatures. Evaporation only occurs from the Surface of Water. So we are very interested in the temperatures of water especially when these temperatures deviate from seasonal norms thus creating an anomaly. The geographical distribution of the anomalies is very important.
To a substantial extent, the temperature anomalies along the Equator have disproportionate impact on weather so we study them intensely and that is what the ENSO (El Nino - Southern Oscillation) cycle is all about.
Subsurface water can be thought of as the future surface temperatures. They may have only indirect impacts on current weather but they have major impacts on future weather by changing the temperature of the water surface.
Winds and Convection (evaporation forming clouds) is weather and is a result of the Phases of ENSO and also a feedback loop that perpetuates the current Phase of ENSO or changes it. That is why we monitor winds and convection along or near the Equator especially the Equator in the Eastern Pacific. 

Starting with Surface Conditions.

TAO/TRITON GRAPHIC (a good way of viewing data related to the part of the Equator and the waters close to the Equator in the Eastern Pacific where we monitor to determining the current phase of ENSO. It is probably not necessary to follow the discussion below, but here is a link to TAO/TRITON terminology.

And here is the current version of the TAO/TRITON Graphic. The top part shows the actual temperatures, the bottom part shows the anomalies i.e. the deviation from normal.

Current SST and wind anomalies

Location Bar for Nino 3.4 Area Above and Below
------------------------------------------------  A       B       C      D       E       -----------------

 

The pattern now is cool water along the Equator and to the south with warmer water north of the Equator. This probably will when I do the calculations average our to Neutral.

The below table only looks at the Equator and shows the extent of anomalies along the Equator. The ONI Measurement Area is the 50 degrees of Longitude between 170W and 120W and extends 5 degrees of Latitude North and South of the Equator so the above table is just a guide and a way of tracking the changes.The top rows show El Nino anomalies. The two rows just below that break point contribute to ENSO Neutral.

Subareas of the Anomaly

Westward Extension

 

Eastward Extension

 

Degrees of Coverage

Total   

Portion in Nino 3.4 Measurement Area

These Rows below show the Extent of El Nino Impact on the Equator

1C to 1.5C (strong)

LAND

LAND

0

0

+0.5C to +1C (marginal)

LAND

LAND

0

0

These Rows Below Show the Extent of ENSO Neutral Impacts on the Equator
0.5C or cooler Anomaly (warmish neutral)

170E

175W

0

0

0C or cooler Anomaly (coolish neutral)

175W

150W

25

25

These Rows Below Show the Extent of La Nina Impacts on the Equator.
-0.5C or cooler Anomaly

150W

LAND

30

25

-1.0C or cooler anomaly

LAND

LAND

0

0

 

My Calculation of the Nino 3.4 Index

I calculate the current value of the Nino 3.4 Index each Monday using a method that I have devised. To refine my calculation, I have divided the 170W to 120W Nino 3.4 measuring area into five subregions (which I have designated from west to east as A through E) with a location bar shown under the TAO/TRITON Graphic). I use a rough estimation approach to integrate what I see below and record that in the table I have constructed. Then I take the average of the anomalies I estimated for each of the five subregions.

So as of Monday September 4, in the afternoon working from the September 3 TAO/TRITON report [Although the TAO/TRITON Graphic appears to update once a day, in reality it updates more frequently.], this is what I calculated.

Calculation of ONI from TAO/TRITON Graphic
Anomaly Segment Estimated Anomaly
  Last Week This Week
A. 170W to 160W +0.4 +0.0
B. 160W to 150W +0.3 +0.0
C. 150W to 140W +0.4  0.0
D. 140W to 130W  0.0  0.0
E. 130W to 120W -0.5 -0.2
Total +0.6  0.0
Total divided by five i.e. the Daily Nino 3.4 Index (+0.6)/5 = +0.1 (0.0)/5 = 0.0

 

My estimate of the daily Nino 3.4 SST anomaly tonight is 0.0 which is truly an ENSO Neutral Value.  NOAA has reported the weekly Nino 3.4 to be -0.2 which is an ENSO Neutral value.
Nino 4.0 is reported the same at +0.2. Nino 3 is also the same -0.4. Nino 1 + 2 which extends from the Equator south rather than being centered on the Equator is reported much  higher at -0.2 which is a surprise. It was up there close to 3 at one time so this index has been declining quite a bit and also fluctuating quite a bit which is not surprising as it is the area most impacted by the Upwelling off the coast. So it is an indication of the interaction between surface water and rising cool water. Thus it is subject to larger changes. Most likely it will be negative for a while and is negative this week but just not nearly as negative as last week.
I am only showing the currently issued version of the NINO SST Index Table as the prior values are shown in the small graphics on the right with this graphic. Notice that all the indices have been declining. The same data in table form but going back a couple of more years can be found here.

September 4, 2017 Nino Readings

This is probably the best place to AGAIN express the thought that this way of measuring an ENSO event leaves a lot to be desired. Only the surface interacts with the atmosphere and is able to influence weather. The subsurface tells us how long the surface will remain cool (or warm). Anomalies are deviations from "Normal". NOAA calculates and determines what is "Normal" which changes due to long ocean cycles and Global Warming. So to some extent, the system is "rigged". Hopefully it is rigged to assist in providing improved weather forecasts. But to assume that any numbers reported can be assumed to be accurate to a high level of precision is foolhardy. It is strange to me that the Asian forecasting services generally conclude that that this cool ENSO Phase is not a La Nina but a near La Nina and NOAA concludes it is a La Nina. It is the same ocean. The reported readings are very close but the Asian readings are generally slightly higher (less La Nina-ish) than the NOAA reading and their cut-off points for declaring a La Nina are a bit different and the parts of the Equator they look at are a bit different. It might be explained by what part of the ENSO pattern impacts their area of geography but it just seems to me that NOAA has been a bit over eager. And I wonder why.

Sea Surface Temperature and Anomalies

It is the ocean surface that interacts with the atmosphere and causes convection and also the warming and cooling of the atmosphere. So we are interested in the actual ocean surface temperatures and the departure from seasonal normal temperatures which is called "departures" or "anomalies". Since warm water facilitates evaporation which results in cloud convection, the pattern of SST anomalies suggests how the weather pattern east of the anomalies will be different than normal.

September 4, 2017 Equatorial Pacific SST Anomalies

A major advantage of the Hovmoeller method of displaying information is that it shows the history so I do not need to show a sequence of snapshots of the conditions at different points in time. This Hovmoeller provides a good way to visually see the evolution of this ENSO event. I have decided to use the prettied-up version that comes out on Mondays rather that the version that auto-updates daily because the SST Departures on the Equator do not change rapidly and the prettied-up version is so much easier to read.
The bottom of the Hovmoeller which shows the current readings is now almost totally a mix of light blue and white. White is Neutral but the small amount of light Blue is where the temperature is in the marginal La Nina range. Remember the +5, -5 degree strip around the Equator that is being reported in this graphic. So it is the surface but not just the Equator. One now sees more white than light yellow in the Nino 3.4 Measurement  Area and some blue no longer restricted to east of 120W. So the Nino 3.4 Index is likely to be negative but still remain in the neutral range or perhaps not and become marginally La Nina. There is a curious brownish area between 150E and 160E worth watching.
Week to week there have been no substantial changes. It was until recently ENSO Neutral with a warm bias. But since the end of July this has changed and you can see that in this Hovmoeller Graphic. The bottom sentence in the legend to the left of the graphic proper says it all.

This graphic is more focused on the Equator and looks down to 300 meters rather than just being the surface.

September 4, 2017 Upper Ocean Heat Anoma

The bottom of the Hovmoeller shows the current situation. If you look from the bottom of the graphic up you can see that any La Nina conditions (which NOAA declared to be a full La Nina event and we disagree) ended in December. At any rate the 2016 Cool Event is long gone. Successive Kevin waves early in 2017 which some thought might be initiating an El Nino in retrospect were not very impressive. We now see a blue (cool) area. NOAA has decided to label it an upwelling Kelvin wave and that probably is appropriate. It is not real impressive but it is there. 

Let us look in more detail at the Equatorial Water Temperatures.

We are now going to look at a three-dimensional view of the Equator and move from the surface view and an average of the subsurface heat content to a more detailed view from the surface down  This graphic provides both a summary perspective and a history (small images on the right). 

.September 4, 2017 Kelvin Wave Analysis.

We now have no warm water near the surface in the area where the Nino 3.4 Index is measured. There is another graphic that shows it better which we will examine soon. There may not be enough cool water at depth to fully flip the situation to La Nina other for a few months which is not long enough to be a La Nina but simply to create La Nina conditions for a month or two. But we will be on the cool side of Neutral with nothing to the west suggesting any change in the near term. There is cool water at depth from 165W to 95W so we should expect lower Nino 3.4 readings. JAMSTEC it seems is paying attention to that yellow/orange area at about 150E which I gather they believe will this winter record as Neutral with a warm bias. We observed that small area on an earlier graphic.
Anomalies are strange. You can not really tell for sure if the blue area is colder or warmer than the water above or below. All you know is that it is cooler than usual for this time of the year. A later graphic will provide more information. Aside from buoyancy the currents tend to bring water from that depth up to the surface mostly farther east.

Now for a more detailed look (there is some redundancy with the above graphic). Notice by the date of the graphic (dated August 31, 2017) that the lag in getting this information posted so the current situation may be a bit different than shown although this graphic was just updated this afternoon. The date shown is the midpoint of a five-day period with that date as the center of the five-day period.

Below is the pair of graphics that I regularly provide.

The bottom graphic shows the absolute values, the upper graphic shows anomalies compared to what one might expect at this time of the year in the various areas both 130E to 90W Longitude and from the surface down to 450 meters. At different times and today in particular, I have discussed the difference between the actual values and the deviation of the actual values from what is defined as current climatology (which adjusts every ten years except along the Equator where it is adjusted every five years) and how both measures are useful for other purposes.

Subsurface Heat Anomalies

Re the top graphic, let us first look at surface temperature anomalies. Almost the entire surface of the Equatorial Pacific has a surface temperature consistent with ENSO Neutral with an occasional cooler area. Subsurface Temperature Anomalies: There is a lot of cool water below 50 meters, especially between 165W and 95W, but perhaps not enough to cause a La Nina (insufficient duration), but enough to cause La Nina Conditions for this winter. In places the cool subsurface water is reaching the surface.
The bottom half of the graphic (Absolute Values which highlights the Thermocline) is now more useful as we track the transition from last winter's ENSO Cool Event to ENSO Neutral to ENSO Neutral with a warm bias which may possibly become an El Nino. More likely we will soon see the situation change to ENSO Neutral with a warm bias and then to just plain ENSO Neutral. It shows the thermocline between warm and cool water. The 28C Isotherm is now located further west at about 175W. This graphic does not show a 27.5C anomaly which might more precisely indicate where convection is likely to occur. The 27C isotherm is now at 160W. The 25C Isotherm reaches the surface at 135W. What we have is ENSO Neutral but almost La Nina.
The flattening of the Isotherm Pattern is an indication of ENSO Neutral just as the steepening of the pattern indicates La Nina or El Nino depending on where the slope shows the warm or cool pool to be. That flattening has occurred. At this point, we have gone to ENSO Neutral.
The conditions to create an El Nino simply do not exist. The conditions to create a sustainable La Nina also do not appear to exist.  

Here are the above graphics as a time sequence animation. You may have to click on them to get the animation going.

Equatorial Temperature Simulation

Isotherm Simulation

And now Let us look at the Atmosphere.

Low-Level Wind Anomalies near the Equator

Here are the low-level wind anomalies.

Low Level Wlind Anomalies

We now see westerlies all over the Equator which should be favorable for the development of an El Nino but do not seem to be having much of an impact.

And now the Outgoing Long wave Radiation (OLR) Anomalies which tells us where convection has been taking place. 

OLR Anomalies Along the Equator

The pattern has changed. We no longer see suppressed Outgoing Long Wave Radiation (OLR) at the Dateline (no longer dry) but we again see enhanced OLR at 120E ( wet)

And Now the Air Pressure which Shows up Mostly in an Index called the SOI.

This index provides an easy way to assess the location of and the relative strength of the Convection (Low Pressure) and the Subsidence (High Pressure) near the Equator. Experience shows that the extent to which the Atmospheric Air Pressure at Tahiti exceeds the Atmospheric Pressure at Darwin Australia when normalized is substantially correlated with the Precipitation Pattern of the entire World. At this point there seems to be no need to show the daily preliminary values of the SOI but we can work with the 30 day and 90 day values.

Current SOI Readings

The 30 Day Average on August 6 was reported as 3.79 which is an ENSO Neutral value with somewhat of a cool bias i.e. somewhat close to a La Nina value. The 90 Day Average was reported at 1.28 which is an ENSO Neutral value. The change from last week is insignificant. Looking at both the 30 and 90 day averages is useful and right now both are in agreement. They seem to be tracking the Nino 3.4 Index pretty well and reflect the downturn in marginal El Nino Conditions and short-term conditions in the Western Pacific where there there had been a long string of negative values for a while. Now the 30 day average is actually positive i.e. in the direction of a La Nina but still in the Neutral Range.

 

SOI = 10 X  [ Pdiff - Pdiffav ]/ SD(Pdiff)  where  Pdiff   =   (average Tahiti MSLP for the month) - (average Darwin MSLP for the month),  Pdiffav   =   long term average of Pdiff for the month in question, and SD(Pdiff)   =   long term standard deviation of Pdiff for the month in question. So really it is comparing the extent to which Tahiti is more cloudy than Darwin,  Australia.  During El Nino we expect Darwin Australia to have lower air pressure and more convection than Tahiti (Negative SOI especially lower than -7 correlates with El Nino Conditions). During La Nina we expect the Warm Pool to be further east resulting in Positive SOI values greater than +7). 

To some extent it is the change in the SOI that is of most importance. The MJO or Madden Julian Oscillation is an important factor in regulating the SOI and Ocean Equatorial Kelvin Waves and other tropical weather characteristics. More information on the MJO can be found here. Here is another good resource.

Forecasting the Evolution of ENSO

The newly issued on August 18 CPC/IRI fully model-based report is shown on the right The earlier August 10 IRI/CPC Meteorologist survey is shown on the left.

August 11. 2017 CPC/IRI Update two graphics side by side.

Not much change from a week ago. More detail was provided in our August 19, 2017 Seasonal Outlook Update Report which can be accessed here. Remember, if you leave this page to visit links provided in this article, you can return by hitting your "Back Arrow", usually top left corner of your screen just to the left of the URL box.

Here is the primary NOAA model.

CFSv2 spread and bias correct ENSO forecast

Last Monday I froze a portion of the above and added some lines to make reading easier. It is a week out of date but I am showing it again as the overall conclusion has not changed that this may last long enough to be officially declared to be a La Nina.

August 28, 2017 CFSv2 Analysis

Looking at the forecast today it looks like it would if it happened as forecast be declared to be a La Nina since there would have been five overlapping three-month periods with the Nino 3.4 Index being -0.5C or cooler. It is way too soon to draw any conclusions. The estimated current value of the Nino 3.4 Temperature Anomaly after the adjustments have been applied is about -0.4 for the end of August which is ENSO Neutral. But we are starting to see this model flirting with La Nina conditions for a period of time this winter. We have not expected this cool event to last long enough to be declared to be a La Nina but it will be close and it would not take too much to have us change our minds on this.  Click here to see  a month by month version of the same model but without some of the correction methodologies applied. It gives us a better picture of the further out months as we are looking at monthly estimates versus three-month averages. 

From Tropical Tidbits.com

CDAS Legacy System

The above is from a legacy "frozen" NOAA system meaning the software is maintained but not updated. Notice since mid-July the collapse of Nino 3.4 values from the range of 0.5C to 0.6C down to Zero C and then down to -0.6C but recently moved back closer to 0C. .

Forecasts from Other Meteorological Agencies.

Here is the Nino 3.4 report from the Australian BOM (it updates every two weeks)

Australia POAMA ENSO model run

Discussion Issued August 29, 2017

ENSO and Indian Ocean Dipole persist at neutral levels

The El Niño–Southern Oscillation (ENSO) remains neutral. International climate models surveyed by the Bureau suggest the tropical Pacific Ocean is likely to persist at ENSO-neutral levels until at least late 2017. One model, out of eight, predicts cooling of the central equatorial Pacific to occur during summer.

Sea surface temperatures (SSTs) have cooled over much of the central tropical Pacific during the past several weeks, yet have remained within the neutral range. Other indicators of ENSO, such as the Southern Oscillation Index (SOI), cloudiness near the Date Line and trade winds are also at neutral levels.

Here are the July 1 and Aug 1 JAMSTEC Nino 3.4 forecasts side by side.

July 1, 2017 JAMSTEC Nino 3.4 Forecast. August 1, 2017 JAMSTEC Nino 3.4 Forecast

 

As you can see there has been some change but not a lot in the JAMSTEC Nino 3.4 forecast and there is a period of time where JAMSTEC is in the warm range of ENSO Neutral while NOAA is in the cool side of ENSO Neutral bordering on La Nina. So we would expect to have very different forecasts from these two agencies and we did when we reported on that on August 24. .

Here is the discussion from JAMSTEC:

Aug. 25, 2017 Prediction from 1st Aug., 2017

ENSO forecast:

A neutral state in the tropical Pacific will persist until boreal winter. Then, a weak La Niña-like pattern will appear in the spring of 2018.

Indian Ocean forecast:

All ensemble members of SINTEX-F now predict a positive Indian Ocean Dipole [Editor's Note: The Australian BOM does not agree with that forecast see next graphic] ; the ensemble mean prediction suggests that it peaks in boreal fall. In accord to the positive IOD evolution, sea level anomalies are expected to be negative (positive) in the eastern (western) tropical Indian Ocean.

Regional forecast:

On a seasonal scale, most part of the globe will experience a warmer-than-normal condition, while some parts of central Russia will experience a colder-than-normal condition in the boreal fall.

As regards to the seasonally averaged rainfall, a wetter-than-normal condition is predicted for some parts of East Africa and West Africa during the boreal fall, whereas most parts of Indonesia, Australia, eastern China, U.S, and Brazil will experience a drier condition during the boreal fall. Those are partly due to the positive Indian Ocean Dipole.

Most parts of Japan will experience warmer-than-normal conditions in the boreal fall. The wind and pressure anomalies averaged in September-November suggest that Japan might be covered by an equivalent barotropic high. Those may be due to the combined effect of the “monsoon-desert mechanism” of the positive Indian Ocean Dipole and the “Silk Road pattern” along the Asian jet.

Indian Ocean IOD (It updates every two weeks)

The IOD Forecast is indirectly related to ENSO but in a complex way.

IOD POAMA Model Run

Discussion Issued August 29, 2017

The Indian Ocean Dipole (IOD) is neutral, though index values have generally been above zero for the past several months. The weekly index value to 27 August was +0.34 °C. Most climate models suggest a neutral IOD is likely to continue. However, two of the six climate models surveyed suggest a positive IOD may develop during spring. Positive IOD events are typically associated with below average winter–spring rainfall, and increased spring–summer fire potential over central and southern Australia.

It is important to understand how and where the IOD is measured.

IOD Measurement Regions

IOD Positive is the West Area being warmer than the East Area (with of course many adjustments/normalizations). IOD Negative is the East Area being warmer than the West Area.  Notice that the Latitudinal extent of the western box is greater than that of the eastern box. This type of index is based on observing how these patterns impact weather and represent the best efforts of meteorological agencies to figure these things out. Global Warming may change the formulas probably slightly over time but it is costly and difficult to redo this sort of work because of long weather cycles.

D. Putting it all Together.

At this time it would seem that the more likely deviation from Neutral right now would be in the direction of a La Nina but we do not believe that there will be a sufficiently long period of La Nina Conditions for a La Nina to be declared but the La Nina Conditions will definitely impact the Boreal Winter.

Forecasting Beyond Five Years.

So in terms of long-term forecasting, none of this is very difficult to figure out actually if you are looking at say a five-year or longer forecast.

The research on Ocean Cycles is fairly conclusive and widely available to those who seek it out. I have provided a lot of information on this in prior weeks and all of that information is preserved in Part II of my report in the Section on Low Frequency Cycles 3. Low Frequency Cycles such as PDO, AMO, IOBD, EATS.   It includes decade by decade predictions through 2050. Predicting a particular year is far harder.

The odds of a climate shift for the Pacific taking place has significantly increased. It may be in progress. The AMO is pretty much neutral at this point (but more positive i.e. warm than I had expected) so it may need to become a bit more negative for the "McCabe A" pattern to become established. That seems to be slow to happen so I am thinking we need at least a couple more years for that to happen. So our assessment is that the standard time for Climate Shifts in the Pacific are likely to prevail and it most likely will be a gradual process with a speed up in less than five years but more than two years.

E. Relevant Recent Articles and Reports

Weather in the News

Australia Weighs in on Harvey and Houston

Statista believes that storms are the most powerful force of Nature [Editor's Note: They seem to not know about insects or earthquakes or Tsunamis etc]

Weather Research in the News

Nothing to Report

Global Warming in the News

Nothing to Report

F. Table of Contents for Page II of this Report Which Provides a lot of Background Information on Weather and Climate Science  

The links below may take you directly to the set of information that you have selected but in some Internet Browsers it may first take you to the top of Page II where there is a TABLE OF CONTENTS and take a few extra seconds to get you to the specific section selected. If you do not feel like waiting, you can click a second time within the TABLE OF CONTENTS to get to the specific part of the webpage that interests you.

1. Very High Frequency (short-term) Cycles PNA, AO,NAO (but the AO and NAO may also have a low frequency component.)

2. Medium Frequency Cycles such as ENSO and IOD

3. Low Frequency Cycles such as PDO, AMO, IOBD, EATS.

4. Computer Models and Methodologies

5. Reserved for a Future Topic  (Possibly Predictable Economic Impacts)

G. Table of Contents of Contents for Page III of this Report  - Global Warming Which Some Call Climate Change.  

The links below may take you directly to the set of information that you have selected but in some Internet Browsers it may first take you to the top of Page III where there is a TABLE OF CONTENTS and take a few extra seconds to get you to the specific section selected. If you do not feel like waiting, you can click a second time within the TABLE OF CONTENTS to get to the specific part of the webpage that interests you.

1. Introduction

2. Climate Impacts of Global Warming

3. Economic Impacts of Global Warming

4. Reports from Around the World on Impacts of Global Warming

H. Useful Background Information

The current conditions are measured by determining the deviation of actual sea surface temperatures from seasonal norms (adjusted for Global Warming) in certain parts of the Equatorial Pacific. The below diagram shows those areas where measurements are taken.

El Nino Zones

NOAA focuses on a combined area which is all of Region Nino 3 and part of Region Nino 4 and it is called Nino 3.4. They focus on that area as they believe it provides the best correlation with future weather for the U.S. primarily the Continental U.S. not including Alaska which is abbreviated as CONUS. The historical approach of measurement of the impact of the sea surface temperature pattern on the atmosphere is called the Southern Oscillation Index (SOI) which is the difference between the atmospheric pressure at Tahiti as compared to Darwin Australia. It was convenient to do this as weather stations already existed at those two locations and it is easier to have weather stations on land than at sea. It has proven to be quite a good measure. The best information on the SOI is produced by Queensland Australia and that information can be found here. SOI is based on Atmospheric pressure as a surrogate for Convection and Subsidence. Another approach made feasible by the use of satellites is to to measure precipitation over the areas of interest and this is called the El Nino–Southern Oscillation (ENSO) Precipitation Index  (ESPI).  We covered that in a weekly Weather and Climate Report which can be found here. Our conclusion was that ESPI did not differentiate well between La Nina and Neutral. And there is now a newer measure not regularly used called the Multivariate ENSO Index (MEI). More information on MEI can be found here. The jury is still out on MEI and it it is not widely used. 

The below diagram shows the usual location of the Indo-Pacific Warm Pool. When the warm water shifts to the east we have an El Nino; to the west a La Nina.

Western Pacific Warm Pool

Click for Source

Interaction between the MJO and ENSO

This Table is a first attempt at trying to relate the MJO to ENSO

  El Nino La Nina MJO Active Phase MJO Inactive Phase
Relationship of MJO and ENSO
Eastern Pacific Easterlies
  • Weaker
  • Stronger
  • Part of Decay Process
  • Counteracts Easterlies
  • Enhances Easterlies
Western Pacific Westerlies
  • Stronger
  • May Create or Stimulate the Onset of El Nino via Kelvin Waves
  • Weaker
  • Part of Decay Process
  • Strengthens Westerlies
  • Weakens Westerlies
MJO Active Phase
  • More  likely
  • Stimulates
  • Less likely and weak
  • Retards development of a new La Nina
  • Stimulates the Jet Stream
 
MJO Inactive Phase
  • Less Likely
  • Suppresses
  • More likely but weak
  • Accelerates development of a new La Nina and the Decline of a mature La Nina
 
  • Slows the Jet Stream and can induce a Split Stream especially during a La Nina

 

Table needs more work. Is intended to show the interactions. What is more difficult is determining cause and effect. This is a Work in Progress. 

History of ENSO Events

With respect to relating analog dates to ENSO Events, the following table might be useful. In most cases this table will allow the reader to draw appropriate conclusions from NOAA supplied analogs. If the analogs are not associated with an El Nino or La Nina they probably are not as easily interpreted. Remember, an analog is indicating a similarity to a weather pattern in the past. So if the analogs are not associated with a prior El Nino or prior La Nina the computer models are not likely to generate a forecast that is consistent with an El Nino or a La Nina.

  El Ninos La Ninas
  Start Finish Max ONI PDO AMO Start Finish Max ONI PDO AMO
            DJF 1950 J FM 1951 -1.4 - N
T   JJA 1951  DJF     1952 0.9 - +          
   DJF 1953  DJF     1954 0.8 - + AMJ 1954  AMJ 1956 -1.6 - +
M MAM 1957  JJA     1958 1.7 + -          
M SON 1958 JFM     1959 0.6 + -          
M   JJA 1963 JFM     1964 1.2 - - AMJ 1964  DJF 1965 -0.8 - -
M  MJJ 1965 MAM    1966 1.8 - - NDJ 1967 MAM 1968 -0.8 - -
M OND 1968 MJJ      1969 1.0 - -          
T  JAS 1969  DJF     1970 0.8 N -  JJA 1970  DJF 1972 -1.3 - -
T AMJ 1972 FMA     1973 2.0 - - MJJ 1973 JJA 1974 -1.9 - -
            SON 1974 FMA 1976 -1.6 - -
T ASO 1976 JFM     1977 0.8 + -          
M ASO 1977 DJF      1978 0.8 N            
M SON 1979 JFM     1980 0.6 + -          
T MAM 1982  MJJ     1983 2.1 + - SON 1984 MJJ 1985 -1.1 + -
M ASO 1986  JFM    1988 1.6 + - AMJ 1988 AMJ 1989 -1.8 - -
M MJJ 1991  JJA     1992 1.6 + -          
M SON 1994  FMA    1995 1.0 - - JAS\ 1995 FMA 1996 -1.0 + +
T AMJ 1997  AMJ    1998 2.3 + + JJA  1998 FMA 2001 -1.6 - +
M MJJ 2002  JFM    2003 1.3 + N          
M  JJA 2004 MAM    2005 0.7 + +          
T ASO 2006 DJF      2007 0.9 - + JAS  2007  MJJ 2008 -1.4 - +
M JJA 2009 MAM     2010 1.3 N + JJA  2010 MAM 2011 -1.3 + +
            JAS 2011 JFM  2012 -0.9 - +
T MAM 2015 AMJ     2016 2.3 + N  JAS 2016 NDJ  2016 -0.8*  + +

 

*The GEI Weather and Climate Report does not accept this as a legitimate La Nina. It is not unusual for different Meteorological Agencies to maintain different lists of El Ninos and La Ninas. This is usually because the criteria for classification differ slightly. Obviously the GEI Weather and Climate Report has no standing but nevertheless for any analysis we do, we will either not include or asterisk this La Nina to indicate that NOAA  has it on their list and we consider that to be Fake News. The alternative is to conclude that the other Meteorological Agencies are not able to measuring things correctly. .

ONI Recent History

ONI History Updated on September 4, 2017

Another neutral reading. The MJJ reading was adjust downward from 0.3 to 0.2 a minor change. The full history of the ONI readings can be found here. The MEI index readings can be found here.

Four Quadrant Jet Streak Model Read more here This is very useful for guessing at weather as a trough passes through.

If the centripetal accelerations owing to flow curvature are small, then we can use the "straight" jet streak model. The schematic figure directly below shows a straight jet streak at the base of a trough in the height field. The core of maximum winds defining the jet streak is divided into four quadrants composed of the upstream (entrance) and downstream (exit) regions and the left and right quadrants, which are defined facing downwind.


Isotachs are shaded in blue for a westerly jet streak (single large arrow). Thick red lines denote geopotential height contours. Thick black vectors represent cross-stream (transverse) ageostrophic winds with magnitudes given by arrow length. Vertical cross sections transverse to the flow in the entrance and exit regions of the jet (J) are shown in the bottom panels along A-A' and B-B', respectively. Convergence and divergence at the jet level are denoted by "CON" and "DIV". "COLD" and "WARM" refer to the air masses defined by the green isentropes.

[Editor's Note: There are many undefined words in the above so here are some brief definitions. Isotachs are lines of equal wind speed. Convergence is when there is an inflow of air which tends to force the air higher with cooling and cloud formation. Divergence is when there is an outflow of air which tends to result in air sinking which causes drying and warming, Confluence is when two streams of air come together. Diffluence is when part of a stream of air splits off.] 

Click here for a list of Sig Silber's Weather Posts

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