September 17, 2018 Weather and Climate Report

Written by Sig Silber

Although Florence deservedly commands the bulk of the attention, an unnamed tropical low has recently been impacting Texas and is forecast to take a long-cut through Mexico to impact Arizona and perhaps New Mexico also. There is additional potential tropical activity that may impact Arizona and New Mexico later this week. The British Isles are getting a quick visit from the remnant of Helene. Meantime, the forecast El Nino is staging a sit-down strike claiming that if the MJO will not be active, at least the Easterlies should slacken off if we want to have an El Nino prior to December.

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Florence

We are still covering Florence and other Tropical Events in more depth and with frequent updates here. That will only continue for another day to so.

But this graphic is useful as a summary of what the impacts over the next three days will be although not all of the impacts are related to Florence or the much least intense tropical event impacting Texas.

New Tropical Low

El Nino

If you do not happen to have a supercomputer in your home office or access to one at work you might just want to look at a graphic and use your intellect which does not cost a lot of money.

But the warm anomaly has moved east enough to be reflected in this graphic

We now provide our usual summary first for temperature and then for precipitation of small images of the three short-term maps. You can click on these maps to see larger versions. The easiest way to return to this report is by using the “Back Arrow” usually found top left corner of your screen to the left of the URL Box. Larger maps are available later in the article with the discussion and analysis.

Sometimes it is useful to see the evolution of the forecasts from the 1 – 5 Day,  6 – 10 Day (which NOAA considers to be Week-1 of their intermediate forecast) , 8 – 14 Day (which NOAA considers to be Week-2) and Week 3 and 4 (which after being issued overlap with Week-2). I do not have comparable maps for the Day 1 – 5 forecast in the same format as the three maps we generally work with. What I am showing for temperature  is the Day 3 Maximum Temperature and for precipitation the five-day precipitation: the latter being fairly similar in format to the subsequent set of the maps I present each week but showing absolute QPF (inches of precipitation) not QPF deviation from Normal.

First Temperature

This shows magnitude rather than probability of  being higher or lower than Normal and shows the middle day of the five day period.	Fairly stable but deamplifying pattern. Possibly there is shown a slight shift east, Today’s NOAA discussion suggests this but I do not see it in the graphics.		↑ ←  The transition from the 8 -14 day forecast shown above to the week 3/4 forecast depends on a renewal of the Monsoon which to me seems unlikely.

And then Precipitation

The five day QPF is shown above.The units are different than the other maps i.e. in units of precipitation (inches) not probabilities of exceeding or being less than climatology.	Perhaps a stable pattern. But  also deamplifying Again the NOAA discussion suggests a shift to the east but it specifies the latter part of this 8 – 14 day period so it may not show up well in this graphic.		↑ ←  The transition from the 8 -14 day forecast shown above to the week 3/4 shown to the left like temperature is based on a resumption of the Monsoon which may not happen.

A. Now we will begin with our regular approach and focus on Alaska and CONUS (all U.S.. except Hawaii).

Water Vapor.

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

You can see from this animation that there has not been much moisture entering CONUS from the Pacific. There is a bit impacting the Northwest.

Tonight, Monday September 17, 2018, as I am looking at the above graphic, We see activity in Mexico but not much entering CONUS except agains the Northwest.

his 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. You can convert this graphic into a flexible forecasting tool by clicking here. One can obtain views of different geographical areas by clicking here.

And Now the Day One and Two CONUS Forecasts

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. 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.

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.

What is Behind the Forecasts? Let us try to understand what NOAA is looking at when they issue these forecasts.

Below is a graphic which highlights the forecasted surface Highs and the Lows re air pressure on Day 7. The Day 3 forecast can be found here. the Day 6 Forecast can be found here. Actually all the small graphics below can be clicked on to enlarge them.

When I look at this Day 7 forecast, we see the Hawaiian High with surface central pressure of 1028 hPa. The Aleutian Low is weak with surface central pressure of 1004 hPa and it is located over the western Aleutians. To the north, there is an Arctic High with surface central pressure of 1012 hPa. Further east, over Greenland there is a High with surface central pressure of 1024 hPa. We can locate the Bermuda High with surface central pressure of at least 1020 hPa. South of Greenland there is a large low with surface central pressure of 996 hPa. The Four Corners High has a surface central pressure of 1016 hPa. It is fairly far north for this time of the year. To the northwest of the Four Corners High there is a low and a trough. There is also an inverted trough entering from Mexico with surface central pressure of 1008 hPa. These features in the Southwest suggest an upswing in Monsoon activity.

I provided this 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 7. It is not the current situation.

The table below showing the Day 3, Day 4, Day 5, Day 6 and Day 7 of this graphic can be useful in thinking about how the pattern of Highs and Lows is expect to move during the week.

From left to right and then down, Days 3 and 4 top row, Days 5 and 6 second row and Day 7 to the right. These are small images but you can if you want click on them and get larger images but even with the small images you can trace the evolution of the pattern. The graphics update but my commentary below does not so it is just a guide for how to read these graphics.
Things to look for in general are the position and strength of the Aleutian Low, the Hawaiian High and any troughs especially if they extend far to the south and are over water.

Looking at the current activity of the Jet Stream.  The below graphics and the above graphics are very related.

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.  I have not provided the ability to click to get larger images as I believe the smaller  images shown are easy to read.

Current	Day 5
.You can see that trough from the Pacific	Right now it is primarily zonal and far north

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.

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.

500 MB Mid-Atmosphere View

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. Thinking about clockwise movements around High Pressure Systems and counter- clockwise movements around Low Pressure Systems provides a lot of information.

Here is the whole suite of similar maps for Days 3, 4, 5, 6 and repeated for Day 7.  It is quite complicated.

Day 3 Above, 6 Below	Day 4 Above,7 Below	Day 5 Above.

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

 Four – Week Outlook: Looking Beyond Days 1 to 5, What is the Forecast for the Following Three + Weeks?

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

6 – 10 Day Temperature Outlook issued today (Note the NOAA Level of Confidence in the Forecast Released on September 17, 2018 was 4 out of 5

8 – 14 Day Temperature Outlook issued today (Note the NOAA Level of Confidence in the Forecast Released on September 17, 2018 was 4 out of 5).

–

Looking further out.

Now – Precipitation

6 – 10 Day Precipitation Outlook Issued Today (Note the NOAA Level of Confidence in the Forecast Released on September 17, 2018 was 4 out of 5)

8 – 14 Day Precipitation Outlook Issued Today (Note the NOAA Level of Confidence in the Forecast Released on September 17, 2018 was 4 out of 5)

Looking further out.

Here is the 6 – 14 Day NOAA discussion released today September 17 and the Week 3 – 4 discussion issued on September 14

6-10 DAY OUTLOOK FOR SEP 23 – 27 2018

TODAY’S 06Z GEFS, 00Z ECMWF, AND 00Z CANADIAN MODEL ENSEMBLE MEANS ARE IN GOOD AGREEMENT OF THE MEAN 500-HPA HEIGHT PATTERN FOR THE 6-10 DAY PERIOD. THE MOST PROMINENT FEATURES ARE A BROAD RIDGE OVER THE EASTERN 2/3RDS OF THE CONUS, A POSITIVELY TILTED TROUGH OVER THE PACIFIC NORTHWEST, AND A RIDGE OVER ALASKA. THIS PREDICTED PATTERN RESULTS IN ABOVE NORMAL HEIGHTS FOR THE CENTRAL AND EASTERN CONUS, BELOW NORMAL HEIGHTS FOR THE PACIFIC NORTHWEST, AND ABOVE NORMAL HEIGHTS OVER ALASKA. THERE ARE SOME SUBTLE DIFFERENCES AMONG THE MODELS, WITH THE 00Z ECMWF ENSEMBLES SHOWING A MORE AMPLIFIED PATTERN THAN THE 06Z GEFS AND THE 00Z CANADIAN ENSEMBLES. THE DETERMINISTIC RUNS OF THE 00Z AND 06Z GFS, HOWEVER, ALSO BOTH SHOW A MORE AMPLIFIED PATTERN AGREEING WITH THE ECMWF ENSEMBLES. THE AFOREMENTIONED UPPER LEVEL FEATURES ARE PROJECTED TO BEGIN TO SHIFT EASTWARD TOWARD THE END OF THE PERIOD.

ABOVE NORMAL TEMPERATURES ARE FAVORED FOR MUCH OF THE CONUS AND ALASKA DUE TO THE POSITIVE HEIGHT ANOMALIES. THE EXCEPTIONS ARE THE WEST COAST EXTENDING INTO THE NORTHERN ROCKIES AS WELL AS PARTS OF THE NORTHERN PLAINS. WEAK TROUGHING OFF THE WEST COAST WILL FAVOR BELOW NORMAL TEMPERATURES IN THESE REGIONS.  ADDITIONALLY, TELECONNECTIONS WITH THE POSITIVE 500-HPA HEIGHT ANOMALY OVER ALASKA FAVORS THE HIGHEST PROBABILITIES OF BELOW NORMAL TEMPERATURES OVER NORTHERN CALIFORNIA AND MONTANA. OVER NORTHERN NEW ENGLAND, NEAR NORMAL TO SLIGHTLY BELOW NORMAL TEMPERATURES ARE FAVORED DUE TO DECREASED HEIGHT ANOMALIES AND A WESTERLY FLOW OUT OF SOUTHERN CANADA.  

THE TROUGH IN THE NORTHWEST WILL BE THE MAIN FOCUS AREA FOR ABOVE NORMAL PRECIPITATION CHANCES FOR THE 6-10 DAY PERIOD WITH THE MEAN STORM TRACK ACROSS THE NORTHERN PART OF THE CONUS. MODEL SIMULATIONS ARE NO LONGER FAVORING THE REDEVELOPMENT OF TROPICAL STORM ISAAC BUT RETURN FLOW AROUND HIGH PRESSURE IN THE EASTERN CONUS MAY STILL ENHANCE PRECIPITATION ACROSS THE WESTERN GULF COAST.  DYNAMICAL MODEL GUIDANCE IS SUPPORTING ELEVATED PRECIPITATION PROBABILITIES ACROSS THE SOUTHEAST AND MID-ATLANTIC FOR THIS PERIOD. HOWEVER, WITH POSITIVE HEIGHT ANOMALIES EXPECTED AND THE MEAN FLOW DISPLACED TO THE NORTH, DRIER CONDITIONS WOULD BE FAVORED, WHICH IS SUPPORTED BY THE STATISTICAL GUIDANCE.  FOR NOW NEAR NORMAL IS FAVORED FOR THESE REGIONS. FOR ALASKA, THE RIDGE WILL BECOME DISPLACED TO THE EAST AND WEAKEN AND ATTENTION WILL TURN TO AN AMPLIFYING TROUGH IN THE BERING SEA WHICH WILL RESULT IN HEIGHTENED ABOVE NORMAL PRECIPITATION PROBABILITIES BEING FAVORED FOR CENTRAL AND WESTERN ALASKA. 

FORECAST CONFIDENCE FOR THE 6-10 DAY PERIOD: ABOVE AVERAGE, 4 OUT OF 5, DUE TO  GOOD OVERALL MODEL AGREEMENT AND CONSISTENCY AMONG PREVIOUS RUNS.  

8-14 DAY OUTLOOK FOR SEP 25 – OCT 01, 2018   

THE 8-14 DAY PERIOD WILL BE CHARACTERIZED BY SIMILAR FEATURES SEEN IN THE 6-10  DAY PERIOD. THE POSITIVE HEIGHT ANOMALIES IN THE EASTERN CONUS WILL REMAIN, SHIFTED SLIGHTLY TO THE EAST RELATIVE TO THE 6-10 DAY PERIOD. THE NEGATIVE HEIGHT ANOMALIES IN THE WESTERN CONUS WILL DIMINISH BUT THE REGION IS STILL EXPECTED TO BE UNDER THE INFLUENCE OF WEAK TROUGHING. OVER ALASKA, THE RIDGE WILL WEAKEN AND BECOME CENTERED INLAND OVER EASTERN ALASKA WITH MEAN TROUGHING ALONG THE WESTERN ALASKAN COAST AND BERING SEA.

ABOVE NORMAL TEMPERATURES ARE LIKELY TO REMAIN IN PLACE FOR MUCH OF THE SOUTHERN CONUS, ESPECIALLY IN THE GREAT BASIN AND THE SOUTHEAST. BELOW NORMAL TEMPERATURES ARE FAVORED IN THE NORTHERN TIER OF THE CONUS. BASED ON TODAY’S 06Z GEFS, THE POSITIVE HEIGHT ANOMALIES IN THE EASTERN CONUS MAY BEGIN TO DIMINISH IN THIS PERIOD, WHICH WOULD RESULT IN MORE INTRUSIONS OF COOLER TEMPERATURES, ESPECIALLY ACROSS NORTHERN AREAS. TEMPERATURES OVER ALASKA ARE FAVORED TO BE MUCH ABOVE NORMAL DUE TO SOUTHERLY FLOW AND ABOVE NORMAL SEA SURFACE TEMPERATURES.

LIKE THE 6-10 DAY PERIOD, THE DYNAMICAL GUIDANCE FAVORS ABOVE NORMAL PRECIPITATION FOR MUCH OF THE CONUS AND ALASKA, WITH THE ONE CAVEAT BEING THE SOUTHWEST. HOWEVER, THE 00Z ECMWF ENSEMBLE MEAN FAVORS BELOW NORMAL FOR THE MID-ATLANTIC EXTENDING INTO THE TENNESSEE VALLEY, AND GIVEN A SIMILAR HEIGHT PATTERN AS THE 6-10 DAY OUTLOOK, IN ADDITION TO STATISTICAL GUIDANCE SUPPORT, NEAR NORMAL PRECIPITATION IS BEING FAVORED FOR THESE REGIONS. ABOVE NORMAL PRECIPITATION IS FAVORED FOR ALASKA DUE TO THE INFLUENCE OF THE AFOREMENTIONED TROUGH TO THE WEST.

FORECAST CONFIDENCE FOR THE 8-14 DAY PERIOD: ABOVE AVERAGE, 4 OUT OF 5, DUE TO  GOOD MODEL AGREEMENT, AND CONTINUITY WITH THE PREVIOUS PERIOD. 

THE NEXT SET OF LONG-LEAD MONTHLY AND SEASONAL OUTLOOKS WILL BE RELEASED ON  SEPTEMBER 20.

Week 3-4 Forecast Discussion Valid Sat Sep 29 2018-Fri Oct 12 2018

The doldrums of the forecasting season continue in terms of predictability for the mid-latitudes at the subseasonal scale. ENSO neutral conditions persist in the equatorial Pacific, while the Madden-Julian Oscillation index appears weak due to competing signals of the low frequency in the Pacific and a Kelvin wave over the Americas. The mid-latitude circulation pattern in recent weeks has been fairly persistent and amplified for the time of year, with anomalous ridging over Alaska and a downstream trough over the Yukon, but there are signs of this pattern starting to break down during the next two weeks. Dynamical model guidance for Week 3-4, the evolving extended range pattern, and long-term trends are the primary guidance used to inform the present Week 3-4 outlook. Among dynamical models used in the present outlook, the ECMWF is favored given its transition from Week-2 being the least drastic.

Model guidance overall shows low amplitude anomalies, typical of the relaxed vorticity gradients during late boreal summer. The CFS breaks down the ridge over Alaska by Week-2, in disagreement with the entire CPC model suite utilized during the extended range period, with negative height anomalies across the state during both Week-3 and Week-4. The ECMWF and JMA maintain this feature, as do most of the Subseasonal Experiment (SubX) models. The resulting downstream impacts are felt in the CFS, with amplified ridging along the Canadian border for Weeks 3-4, while the ECMWF appears to have a better handle with anomalous troughing extending from the Canadian prairies through Hudson Bay. The JMA model favors generally positive height anomalies across the CONUS, potentially tied to the model overplaying decadal trends. Both the ECMWF and JMA maintain anomalous ridging off the Eastern Seaboard in Week 3-4, along with much of the SubX guidance.

The favored pattern in line with the ECMWF solution would support a mean frontal zone extending from the Midwest through New England, with surface high pressure over much of the West and along the eastern seaboard. Given that pattern, the ECMWF anticipates substantial chances of below-normal temperatures from the Northern Plains through the Northeast, which may be overdone given the difficulties observed in recent weeks for cold air built up over Canada to push south into the CONUS. Similarly, the positive height anomalies from the JMA and discounted CFS are at odds with potential cold along the northern tier, resulting in a forecast of equal chances in the outlook. More consistency exists among forecasts for above-normal temperatures over the West and Southeast, given the positive height anomalies favored for these regions. Above-normal temperatures are also favored in Alaska, with southerly flow anticipated for much of the mainland, while well above-normal sea-surface temperatures (SSTs) in the Bering Sea may help to offset anomalous northerly flow across the Aleutians. Model guidance is consistent in indicating an increase in below-normal temperature chances across portions of the Southern Plains, tied to either increased precipitation or the mean front being east of the region, depending on the model.

Forecast ridging across the West Coast supports increased chances of anomalously dry conditions for many areas from the Plains westward. The exception to this is across Arizona, where above-median precipitation odds are increased due to model signals of a surge of moisture into the state from the Gulf of California associated with tropical cyclone activity off of the Baja Peninsula. The enhanced subtropical ridge forecast by model guidance also leads to increased above-median rainfall chances for much of the East, tied to amplified transport of moisture from the Gulf of Mexico, as has been observed in recent weeks. This area was extended slightly westward from what models indicated due to the forecast weakness in the model height fields across the central CONUS, suggesting any potential tropical cyclone activity could be focused towards the western or central Gulf of Mexico coastline. With anomalous ridging favored over the Western CONUS, the storm track appears likely to shift northward into southern Alaska, yielding increased odds of above-median precipitation for portions of the Aleutians, Kenai Peninsula vicinity, and Alaska Panhandle.

Persistent positive SST anomalies continue to surround Hawaii, supporting increased chances of above-normal temperatures and precipitation across the island chain. Dynamical model guidance is similarly unanimous in the increased chances of above-normal temperatures and above-median rainfall for the island chain.

Some Indices of Possible Interest:  We should always remember that the forecast is driven by many factors some of which are conflicting in terms of their impacts. Please pay more attention to the graphics than my commentary which does not update on a regular basis once the article is published. The indices will continue to update.

Below is a graphical explanation of the Arctic Oscillation

AO Positive	AO Negative
There are more impacts than shown here but these are important. Basically the AO+ means the Polar Vortex is blocked from leaving its normal locations	Again there are more impacts than shown here. A0- means Low Pressure allows the Polar Vortex to wander south.

* These graphics are from National Geographic Magazine, March 2000; Sources: Doug Martinson, Wieslaw Maslowski, David Thompson, and John M. Wallace

Here is another set of graphics.

Left: Effects of the Positive Phase of the Arctic Oscillation. Right:Effects of the Negative Phase of the Arctic Oscillation. —Credit: J. Wallace, University of Washington.

NAO Positive	NAO Negative
Notice the strong Icelandic Low and strong Bermuda High but located east of where it is usually found	Notice the weak Icelandic Low and Bermuda High.
There are many variations on a theme when talking about the NAO.	Some use Lisbon or Gibraltar as the sub-arctic reference point. And there appears to be a low-frequency cycle related to the AMO to some extent. Thus the NAO is a lot more complicated than I am able to show here.  I like this explanation better than the graphics I have shown. It better captures the impact of the changing relative strength of the two control factors in the Atlantic namely the Northern and Southern semi-permanent Highs and Lows.

But it gets even more complicated. With a Negative NAO the position of the pattern more east than west or vice versa changes the impacts.

Madden Julian Oscillation (MJO)

The MJO is an area of convective activity along the Equator which circles the globe generally in 30 to 60 days. The location of the convective activity not only impacts the Equator but also the middle latitudes.

There are a lot of models and I try to read the results from all of them.  For access to a variety of models,  I refer readers here. This weekly report summarizes things.  Here is another useful source of information. 

Now we look at two models that I find very helpful. On the first graphic , the light gray shading shows the tracks which fit with 90% of the forecasts and the dark gray shading shows a smaller area that fits with 50% of the forecasts The large dot is the current location.

Analogs to the Outlook.

Now let us take a detailed look at the “Analogs”.

NOAA normally provides two sets of Analogs.

A. Analogs 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 the recent pattern is used to initialize the models to predict the 6 – 14 day Outlook.

B. There is a second set of analogs associated with the Outlook. It compares the forecast (rather than the prior period) to past weather patterns. I have not been regularly analyzing this second set of information. The first set applies to the 5 and 7 day observed pattern prior to today. The second set, relates to the correlation of the forecasted outlook 6 – 10 days out and 8 – 14 days out with similar patterns that have occurred in the past during a longer period that includes the dates covered by the 6 – 10 Day and 8 – 14 Day Outlook. The second set of analogs also has useful information as it indicates that the forecast is feasible in the sense that something like it has happened before. I am not very impressed with that approach. But in some ways both Approach A and B are somewhat similar. I conclude that if the Ocean Condition now are different then the analogs and if the state of ENSO now is different than the analogs that is a reason to have increased lack of confidence in the forecasts and vice versa.

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. But NOAA prefers the first set (A) as it helps them (or at least they think it does) assess the quality of the forecast.

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. It also helps the reader see the impact of the phases of the PDO and AMO which are shown. The first set (A) which is what I am using today applies to the 5 and 7 day observed pattern prior to today.

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

The spread among the analogs from August 27 to September 23 is 27 days which is about the same as last week. 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, and fairly accurate if the dates are reasonably evenly distributed, is about September 9. These analogs are centered on 3 days and 4 days ago (Sept 13 or September 14). So the analogs could be considered to be out of sync by four or five days with respect to weather that we would normally be getting right now. We are getting weather that normally would occur a bit later to the extent the analogs mean anything.

For more information on Analogs see discussion in the GEI Weather Page Glossary.  For sure it is a rough measure as there are so many historical patterns but not enough to be a perfect match with current conditions. I use it mainly to see how our current conditions match against somewhat similar patterns and the ocean phases that prevailed during those prior patterns. If everything lines up I have my own measure of confidence in the NOAA forecast. Similar initial conditions should lead to similar weather. I am a mathematician so that is how I think about models.

Including duplicates, there are zero La Nina Analogs, six El Nino Analogs and four Neutral analogs. The pre-forecast analogs this week are fairly inconclusive but less supportive of McCabe B. Being less supportive of McCabe B is to some extent being supportive of the opposite of McCabe B which is somewhat consistent with the NOAA forecast. Many of the analogs associated with El Nino conditions are Modoki’s which is consistent with the current pattern of warm and cool water in the Nino 3.4 Measurement Area.

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.

In color	Black and White same graphics

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.

Historical Anomaly Analysis

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

A Useful Read

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.

Recent CONUS Weather

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

And the 30 Days ending September 8, 2018	And the 30 Days ending September 15, 2018
You can see the improvement in the Great Plains re precipitation and we see how the Northeast is a lot warmer.	A change is the cool anomaly along the Western Northern Tier. The warm anomaly extends further south. The wet anomaly extends further east. We will start to see the impact of Florence next week.
Remember, these maps are 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

It is Useful to Understand the Semipermanent Pattern that Control our Weather and Consider how These Change from Winter to Summer. These two graphics (click on each one to enlarge) are from a much larger set available from the Weather Channel.  They highlight the position of the Bermuda High which they are calling the Azores High in the January graphic 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 moving into Mid-September and we should be returning from the set of positions shown below for July back slowly to the Winter Pattern. For CONUS, the seasonal repositioning of the Bermuda High and the Pacific High are very significant.

World Forecasts

A. Today (University of Maine)

B  Short-term set for day six but can be adjusted (BOM – Australia)

C. 8 – 14 Day (NOAA/Canada/Mexico Experimental NAEFS))

A. Forecast for Today (you can click on the maps to enlarge them)

And now precipitation

I have not changed the source but it seems that the links I had before (the images were smaller and in a table) were not updating. We will see if this works better.

Additional Maps showing different weather variables can be found here.

B. 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

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

Now Precipitation

C. And now we have experimental 8 – 14 Day World forecasts from the NAEFS Model.

First Temperature

Then Precipitation

Looking Out a Few Months

Here is the precipitation forecast from Queensland Australia:

It is kind of amazing that you can make a worldwide forecast based on just one parameter the SOI and changes in the SOI. This graphic has been updated and now is in line with the actual SOI for June and July. Of interest is generally dry CONUS and belt of wet in the mid Asian Continent and belt of dry for Equatorial Africa and the Middle East. Eastern Asia and Australia are wet.

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. If we want to have a good feel for future weather we need to look at the oceans as our weather mostly comes from oceans and we need to look at

• Surface temperature anomalies (weather develops from the ocean surface and
• The changes in the temperature anomalies since that may provide clues as to how the surface anomalies will change based on the current trend of changes. This is not that easy to do since the oceans are deep, there are many currents, winds have an impact etc. Two ways that are available to use are to look at the change in the situation today compared to the average over a period of time and NOAA also produces a graphic of monthly changes. I use both. The first set of graphics is simply looking at the average compared to today and that is below.

Three Month Average Anomaly	Current Anomaly
By this point La Nina is gone	Traces of El Nino but the Indo-Pacific Warm Pool is cool. I am not convinced an El Nino will materialize.

And when we look in more detail at the current Sea Surface anomalies below, we see a lot of them not just along the Equator related to ENSO.

First the categorization of the current daily SST anomalies.
Mediterranean, Black Sea and Caspian Sea	Western Pacific	West of North America	North and East of North America	North Atlantic
The western Mediterranean is warm The Gulf of Aden and the Arabian Sea are slightly cool	Warm around Kamchatka	Warm Chukchi Sea, Bering Strait and Bering Sea Warm offshore of Alaska Panhandle Warm off Baja	Eastern Hudson Bay cool Great Lakes Warm Cool south of Greenland and Davis Strait. Warm offshore of Nova Scotia down to Cape Hatteras extending far out to sea	Warm north of Scandinavia
Equator	Still looks like Neutral. Even more Neutral than last week.
Africa	West of Australia	North, South and East of Australia	West of South America	East of South America
Cool off west coast of Africa north of the  Equator. Cool south of Gulf of Guinea Slightly warm south of Africa	Cool	Cool to the northwest Cool to the south and southwest	Generally cool from 20S to 40S	Mixed off 30S to 50S

Then we look at the change in the anomalies. The SST anomaly is sort of like the first derivative and the change in the anomaly is somewhat like a second derivative. It tells us if the anomaly is becoming more or less intense.

Here it gets a little tricky as for this graphic red does not mean a warm anomaly but a warming of the anomaly which could mean more warm or less cool and blue does not mean cool but more cool or less warm.
Mediterranean, Black Sea and Caspian Sea	Western North Pacific	West of North America	East of North America	North Atlantic
Eastern Mediterranean cooling Southern Caspian Sea is warming.	Cooling west of Japan and further out to sea.	Warming in Bering Sea Warming around and south of Alaska Warming west of Baja and Mexico .	Cooling Hudson Bay Cooling Davis Straits Warming east of Southeast Coast Warming western Caribbean Warming north of South America	Significant cooling around British Isles and further north.
Equator	Eastern Pacific showing a mixed pattern
Africa	West of Australia	North, South and East of Australia	West of South America	East of South America
Cooling west of North Africa. Mixed pattern west of Africa south of Equator Warming south of Africa Cooling east of Madagascar	Fairly Neutral	Slight cooling to south and east SE of New Zealand	Fairly Neutral	Cooling north of South America Warming offshore at 40S to 50S

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. Notice the change in the PDO in July of 2017 and the stability of the AMO index.

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

 * 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.

Tropical Activity Possibly Impacting CONUS.

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 (new) tropical events are expected to appear in this graphic during the next 48 hours. If that changes, we will provide an update.

Now let us look at the Western Pacific in Motion.

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 clicking U.S. Navy Joint Typhoon Warning Center This (click here to read) is an unofficial private source but one that is easy to read but not working right now. And then there is the Central Pacific Hurricane Warning Center.

In the above graphic, it is difficult to reference the storms to geography. If you are patient and look closely you can see bodies of land under the storms. Mostly I am interested in

1. How much of the tropical activity gets caught up in the westerlies and returns to CONUS and
2. How much of the Asian storms return along the northern route to Alaska and British Columbia.

C. Progress of ENSO

This section is organized into four parts.

1. Current and Recent Sea Surface Temperatures (SST)

2. Current and Recent Equatorial Pacific Subsurface Temperatures

3. History of the Nino 3.4 Readings and forecasts from other Meteorological Agencies.

4. The Surface Air Pressure Pattern that confirms the state of ENSO.

1. Current and Recent Sea Surface Temperatures (SST)

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.

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.

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 shows the current readings. 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.

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

2. Current and Recent Equatorial Pacific Subsurface Temperatures Let us look in more detail at the Equatorial Water Temperatures.

 This graphic provides both a summary perspective and a history (small images on the right).

.

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. These currents are very complicated and made even more so by the uneven nature of the ocean floor. So the exact pattern of where this warm water will erupt is beyond my level of understanding. But it will erupt to the surface in multiple different places.

Now for a more detailed look. Below is the pair of graphics that I regularly provide. The date shown is the midpoint of a five-day period with that date as the center of the five-day period. 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 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.

We now have warm water extending to 110W. Most of this is at depth. One can see why the models predict an El Nino.

The 28C Isotherm is now at 160W, the 27C Isotherm is at 150W, the 25C Isotherm is now at 130W. The 20C Isotherm no longer reaches the surface but the 21C Isotherm does so at 105W.

Tracking the change.

The next graphic basically averages out the anomalies by longitude.

The discussion in this slide says it better than I could. One might compare the current reading to Oct/Nov 2017. The anomaly had returned to zero then reversed for a month and then returned to zero and now has gone positive. It now seems to be declining a bit.

Side by side comparison can be useful

Comparison Week Probably Third Week of December 2017	Current Week

3. History of the Nino 3.4 Readings and forecasts from other Meteorological Agencies.

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 in order 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.

Location Bar for Nino 3.4 Area Above and Below

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 17, in the afternoon working from the September 16 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 Nino 3.4 from TAO/TRITON Graphic

My estimate of the daily Nino 3.4 SST anomaly tonight is +0.4 which is an ENSO Neutral value. NOAA has again reported the weekly Nino 3.4 to be +0.3 which is an ENSO Neutral value. Nino 4 is reported to be a bit cooler than last week at +0.4. Nino 3 is reported to be warner at +0.4. Nino 1 + 2 which extends from the Equator south rather than being centered on the Equator is reported warmer at +0.2 It was close to -3.0 at one time so this index has been declining as an anomaly (rising) 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. 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. The same data in graphic form but going back a couple of more years can be found here.  The full table of values can be found here.

This graphic brings the Nino 3.4 up to date and is easy to read. It may be more reliable than the NOAA readings. And Memorial Day is not a Holiday in Australia.

Here is another way of looking at the TAO/TRITON Graphic. It is a fast way to assess the strength of an ENSO Event and provides a way to track it.  

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.

Forecasting the Evolution of ENSO

The CFS.v2 is not the only forecast tool used by NOAA. The CPC/IRI Analysis which is produced out of The International Research Institute (IRI) for Climate and Society at Columbia University is also very important to NOAA.

Here is the most recent update.

The discussion released with the forecast follows. It can also be found here.

IRI ENSO Forecast CPC/IRI ENSO Update Published: September 13, 2018

El Niño/Southern Oscillation (ENSO) Diagnostic Discussion issued jointly by the Climate Prediction Center/NCEP/NWS and the International Research Institute for Climate and Society

ENSO Alert System Status: El Niño Watch

Synopsis: There is a 50-55% chance of El Niño onset during the Northern Hemisphere fall 2018 (September-November), increasing to 65-70% during winter 2018-19.

ENSO-neutral continued during August, as indicated by a blend of slightly above- and below- average sea surface temperatures (SSTs) across the equatorial Pacific Ocean . Over the last month, the westernmost Niño-4 region was the warmest (latest weekly value was +0.5°C), while the Niño-3 and Niño-3.4 regions were weakly positive, with Niño1+2 remaining negative. Subsurface temperature anomalies (averaged across 180°-100°W) were positive, with an increase in above-average subsurface temperatures in the central Pacific and slight expansion of negative anomalies in the eastern Pacific. Convection returned to near average over the Date Line, and was slightly enhanced over Indonesia . Low-level westerly wind anomalies re-developed across the east-central and western Pacific, although they were only slightly evident in the monthly average. Upper-level wind anomalies were westerly over the eastern Pacific. Overall, the oceanic and atmospheric conditions reflected ENSO-neutral.

The majority of models in the IRI/CPC plume continue to predict the onset of El Niño sometime during the Northern Hemisphere fall and continuing through the winter . The forecasters also favor El Niño formation during the fall, and are leaning toward the more conservative model guidance that indicates a weak El Niño event. The persistence of above-average subsurface temperatures and continuing flare-ups of westerly wind anomalies also support the eventual development of El Niño.In summary, there is a 50-55% chance of El Niño onset during the Northern Hemisphere fall 2018 (September-November), increasing to 65-70% during winter 2018-19 (see the CPC/IRI consensus forecast for the chance of each outcome for each 3-month period).

This discussion is a consolidated effort of the National Oceanic and Atmospheric Administration (NOAA), NOAA’s National Weather Service, and their funded institutions. Oceanic and atmospheric conditions are updated weekly on the Climate Prediction Center web site (El Niño/La Niña Current Conditions and Expert Discussions). Forecasts are also updated monthly in the Forecast Forum section of CPC’s Climate Diagnostics Bulletin. Additional perspectives and analysis are also available in an ENSO blog.

The next ENSO Diagnostics Discussion is scheduled for 11 October 2018.

Sometimes it is useful to compare the new forecast to the old.

This graphic shows a collection of models used by various meteorological agencies to forecast the NINO 3.4 Index. We will have an update on this on Thursday and it will be in our Saturday Seasonal Outlook article.

Forecasts from Other Meteorological Agencies.

Here is the newly issued JAMSTEC Model Forecast.  It suggests a less strong El Nino than their forecast last month.  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.

There will be an updated discussion soon. but we do not have it yet.

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

And the ENSO Outlook Discussion Issued on September 11, 2018

El Niño still possible in 2018

The El Niño–Southern Oscillation (ENSO) remains neutral. However model outlooks continue to indicate El Niño is possible from late spring 2018. When assessed with current observations, the Bureau’s ENSO Outlook stands at El Niño WATCH, meaning there is approximately a 50% chance of El Niño forming in the coming months—double the normal chance.

There were only small changes to most indicators of ENSO in the past fortnight. The central and eastern tropical Pacific Ocean are warmer than average, with greatest warmth in the central to western Pacific (NINO4; +0.6 °C), while water below the surface remains somewhat warmer than average. Atmospheric indicators generally remain neutral, although trade winds are slightly weaker over parts of the western Pacific. A weakening of the trade winds is one of the most important precursors at this point for any possible El Niño, and will be watched closely.

Seven of the eight surveyed models suggest SSTs are likely to reach or exceed El Niño thresholds by the end of spring, with the majority suggesting values will remain at or above the threshold into early 2019. El Niño during spring typically results in below-average rainfall in eastern and northern Australia. In summer, this drying influence retracts to tropical regions of Australia, although the possibility of high temperatures elsewhere remains high.

Regardless of El Niño or positive IOD developing, the climate outlook for spring is for a continuation of drier and warmer than average conditions across eastern and southwest Australia.

Indian Ocean IOD (It updates every two weeks)

Indian Ocean Dipole Outlook  Discussion Issued September 11, 2018

Indian Ocean Dipole outlooks

The Indian Ocean Dipole (IOD) is currently neutral. The weekly index value to 9 September was +0.28 °C.  However, two of six international climate models suggest a positive IOD event may develop before the end of spring. A positive IOD during spring typically reduces rainfall in central and southern Australia, and can exacerbate any El Niño-driven rainfall deficiencies.

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

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.

4. The Surface Air Pressure Pattern that confirms the state of ENSO.

And Now the Air Pressure to Confirm that the Atmosphere is Reacting to the Sea Surface Temperature Pattern. The most Common way to do that is to use 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

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.

And now let us look at the atmosphere.

This graphic shows the Low-Level Wind Anomalies near the Equator. The 850 hPa level is above the surface but close to the surface.	And now the Outgoing Long-wave Radiation (OLR) Anomalies which tell us where convection has been taking place. The bottom of a Hovmoeller graphic shows the most recent readings.
Reds and browns would be suppressed easterlies or enhanced westerlies and are typical of El Nino. It looks pretty neutral.	We see the change in the pattern of suppressed OLR along the Dateline as the La Nina declines. But we now see suppressed OLR further west.

D. Putting it all Together.

At this time, La Nina Conditions along the Equator have come to an end and we are solidly into ENSO Neutral and possibly entering El Nino Conditions. But the drivers of a transition to El Nino are not solidly in place.

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 have significantly increased. It may be in progress. The AMO is pretty much neutral at this point so it may need to become a bit more negative for the “McCabe A” pattern to become established. Our assessment is that the standard time for Climate Shifts in the Pacific is 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. The next El Nino may be the trigger. And of course the next El Nino is project to occur this winter.

E. Relevant Recent Articles and Reports

Weather in the News  

Nothing to Report

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.

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 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 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.

Click for Source

Interaction between the MJO and ENSO

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

History of ENSO Events as measured by the ONI

The new SON reading of +0.1 is clearly an ENSO Neutral reading. 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. It would apply to the states that are at the apex of the trough.

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.]

Here is a time sequence animation. You may have to click on them to get the animation going.

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.

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.

MJO (Madden Julian Oscillation)

The MJO is an area of convective activity along the Equator which circles the globe generally in 30 to 60 days. The location of the convective activity not only impacts the Equator but also the middle latitudes. Here is a good description of the MJO.

This is the source of the analysis of the impact of the MJO on CONUS. “A composite study of the MJO influence on the surface air temperature and precipitation over the Continental United States Shuntai Zhou • Michelle L’Heureux • Scott Weaver • Arun Kumar”

The below shows the various phases of the MJO. Where the above average convection (green) is found is described by one of 8 phases shown below. The dry part of the pattern is shown in brown and is called the Inactive or dry part of the MJO.

The below is the summary analysis for precipitation in the July to September Season. The full data set for all seasons can be found here for Temperature and here for Precipitation. My analysis of that data was that there is not much difference between the level of significance of the temperature and precipitation in the JAS three-month period.