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posted on 25 April 2017

April 24, 2017 Weather and Climate Report - All Too Normal!

Written by Sig Silber

Typical Spring weather. There is a hint of El Nino gaining ground but there are other reasons for thinking that we may be setting up for an active Atlantic Tropical Storm Summer. Generally those two concepts do not coexist well but since Summer happens before Winter it might be possible.

weather.caption


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First some housekeeping information. For those who want the forecasts beyond three months, we recently reported on the recent NOAA and JAMSTEC Seasonal Forecasts and compared them in a Special Update that you can get to by clicking here. More recently we provided an Update on the possible El Nino this Winter that many meteorological models are forecasting. We think it is implausible and our report can be accessed by clicking 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.

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 April 24, 2017, as I am looking at the above graphic, we see the Pacific Trough almost at textbook quality. We also see the Great Lakes weather event which is not directly related.

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. Notice the action impacting the West Coast and also some distance away,  the Great Lakes.

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.
Mostly this evening we see mostly moisture entering CONUS from the Pacific. Perhaps I was incorrect when I said the Pacific Storm and the Great Lakes weather were not connected. The seem to be connected in this graphic.

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

60 Hour Forecast.

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.

U.S.  3 Day to  7 Day Forecasts

Below is a graphic which highlights the forecasted surface Highs and the Lows re air pressure on Day 3. The Day 6 forecast can be found here.

Day 3 Weather Forecast

The Aleutian Low is as I look at this Day 3 forecast yesterday was a large elongated unified low with central surface air pressure of 988 hPa. But today it has fallen apart (three day forecast into two small parts one along the Aleutians with central surface pressure of hPa 1000 and a second part over by Kamchatka with central surface pressure of hPa 992. It is still a large Low Pressure System but no longer well organized. Remember this is a forecast for Day 3 not the current situation. The average sea level air pressure in the winter is 1001 hPa and 994 hPa for a non-split Low. This graphic changes every six hours.
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 again forecasted to be present with central surface air pressure of 1024 hPa. There is thus now for Day 3 a forecast of block on Pacific Storms entering CONUS but this High as forecast yesterday was fairly far south for the three day forecast today has it further north as the Aleutian Low has weakened. You can easily imagine how storms can move between the intersection of a counterclockwise Low Pressure system and a clockwise High Pressure system and thus directing the flow from the Pacific into Oregon. Also seen is a low pressure system over the Great Lakes with surface central pressure of 992 hPa. That should impact CONUS weather.
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 3. It is not the current situation but Day 3 is not very far out.

Now looking at the 5 Day Jet Stream Forecast

Jet Stream Five Days Out .

This is a fairly potent system for the West and may then impact the Northern Tier as it moves storms east and the trough progresses to the east. Remember this is a H3 view meaning a view at 30,000 feet which is about six miles high.

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, 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 lot of moisture in the Plains States. The graphic shows the cumulative precipitation over a seven-day period. Notice that the trough that impacts the Southwest comes and goes with little precipitation impact. That is why the Southwest is called semiarid. Even when storms come through the often bring more wind than precipitation.

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 the Western Trough projected to be approaching the Great Lakes and impacting the enter Mississippi Valley and soon after the East Coast. It is right now a fairly predictable forecast.
Remember this is a forecast for Day 7. Note the 540 Thickness Line re the above discussion of thickness and snow likelihood. This week it looks like the 540 line will not impact CONUS but if there is a change it most likely would impact Maine. Thickness lines near or over 600 tend to suggest very warm temperatures. So that is what we will be focusing on now.

 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 provide the April and three-month AMJ maps which 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.

 

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 April 24, 2017 was 4 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 April 24, 2017 was 3 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 Forecasts

Interpreted on April 24, 2017

April 30 to May 8 May 6 to May 19

Days 6 - 10: CONUS is warm in the far West and in the East and cool in the  Center. Alaska is warm in the North and the Panhandle.

The expanded Southwest is warm, the Southeast is warm and New England is warm. The expanded North Central is cool. Alaska is warm. The transition to the pattern shown in the Week 3 - 4 Forecast from the pattern shown in the 8-14 Day forecast seems to be feasible. Again the forecast for the Southeast seem to be the least likely to be a zonal progression.

Week 2:  As the period evolves, the CONUS pattern shifts to the east. No change is shown for Alaska which is a bit surprising.
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.

 

Now for reference purposes, here 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.

May Early Temperature Outlook Issued on April 20, 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 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 and statistical models 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.

MJJ 2017 Temperature Outlook Issued on April 20, 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 that has the three small images, you can find the larger maps and a discussion that ties the three maps together.  For reference purposes, I then provide the April and three month AMJ maps which are issued and updated less frequently than the first three maps shown.

 Small Images of Precipitation Maps
  8 to 14 Day Weeks 3 and 4
6 to 10 Day 8 - 14 Weeks 3 and 4

 

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 April 24, 2017 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 April 24, 2017 was 3 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 Forecasts

Interpreted on April 24, 2017

April 30 to May 8  May 6 to May 19, 2017
Days 6 -10 The West is  dry and the Eastern 2/3rds of CONUS is wet. Alaska is dry in the North and wet in the South and the Panhandle.

For CONUS the Northwest and the expanded Great Lakes Area is dry. Colorado, New Mexico and Texas are wet. Northern Alaska and the Panhandle are dry. The transition to the pattern shown in the Week 3 - 4 Forecast from the pattern shown in the 8-14 Day forecast seems to be somewhat complicated.

Week 2: For CONUS, the Wet anomaly shifts slightly to the east and thus has a bit less geographical extent. Montana and Wyoming may become wet as moisture finds its way over the Western Ridge. For Alaska the only change is that the North becomes EC.

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.

 

Now for reference purposes 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.

May 2017 Early Precipitation Outlook Issued on April 20, 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 and statistical models 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.

MJJ 2017 Precipitation Outlook Issued on April 20, 2017

Here is the NOAA discussion released today April 24, 2017.

6-10 DAY OUTLOOK FOR APR 30 - MAY 04, 2017

TODAY'S DYNAMICAL MODEL SOLUTIONS FOR THE 6-10 DAY PERIOD ARE IN GOOD AGREEMENT ON THE EXPECTED 500-HPA CIRCULATION PATTERN OVER MOST OF NORTH AMERICA. TROUGHS  ARE PREDICTED OVER THE CENTRAL CONUS AND THE BERING SEA, WHILE RIDGES ARE ANTICIPATED OVER THE WESTERN ATLANTIC AND THE WESTERN CONUS EXTENDING NORTHWARD TO WESTERN CANADA AND ALASKA. THE GFS 6Z ENSEMBLE MEAN IS A BIT OF AN OUTLIER AS IT DEPICTS THE CENTRAL U.S. TROUGH SHEARING APART AND DEAMPLIFYING. ENSEMBLE SPREAD IS MODERATE TO HIGH OVER MOST OF THE FORECAST DOMAIN. TODAY'S OFFICIAL 500-HPA MANUAL HEIGHT BLEND INDICATES NEAR TO ABOVE NORMAL HEIGHTS OVER THE EASTERN CONUS, THE WESTERN CONUS, AND THE ALASKA PANHANDLE, WHILE NEAR TO BELOW NORMAL HEIGHTS ARE EXPECTED OVER THE CENTRAL CONUS AND MUCH OF ALASKA. 

ABOVE NORMAL HEIGHTS TILT THE ODDS TO ABOVE NORMAL TEMPERATURES FOR MUCH OF THE EASTERN U.S. AND PARTS OF THE WESTERN CONUS. BELOW NORMAL HEIGHTS AND/OR ANOMALOUS NORTHERLY FLOW FAVOR BELOW NORMAL TEMPERATURES FOR MUCH OF THE WEST-CENTRAL AND CENTRAL CONUS. ANOMALOUS SOUTHEASTERLY FLOW AND ABOVE NORMAL SEA SURFACE TEMPERATURES ENHANCE PROBABILITIES FOR NEAR TO ABOVE NORMAL TEMPERATURES FOR ALASKA.

THE TROUGH FORECAST OVER THE CENTRAL CONUS FAVORS ABOVE MEDIAN PRECIPITATION FOR MUCH OF THE CENTRAL AND EASTERN CONUS. ABOVE NORMAL HEIGHTS AND ANOMALOUS NORTHERLY FLOW TILT THE ODDS TO BELOW MEDIAN PRECIPITATION FOR PARTS OF THE WESTERN AND SOUTH-CENTRAL LOWER 48 STATES. BELOW NORMAL HEIGHTS AND THE TROUGH FORECAST OVER THE BERING SEA ENHANCE PROBABILITIES OF ABOVE MEDIAN PRECIPITATION FOR THE ALEUTIANS AND MUCH OF SOUTHERN ALASKA, WHILE RIDGING FAVORS BELOW MEDIAN PRECIPITATION FOR PARTS OF NORTHERN ALASKA.

FORECAST CONFIDENCE FOR THE 6-10 DAY PERIOD: ABOVE AVERAGE, 4 OUT OF 5, DUE TO GOOD AGREEMENT ON A MODERATELY AMPLIFIED PATTERN FOR MUCH OF THE FORECAST DOMAIN AND FAIRLY GOOD AGREEMENT AMONG THE FORECAST TOOLS.

8-14 DAY OUTLOOK FOR MAY 02 - 08 2017 

COMPARED TO THE 6-10 DAY PERIOD, THE OVERALL CIRCULATION PATTERN IS EXPECTED TO BE PROGRESSIVE AND DEAMPLIFIED DURING WEEK-2. TROUGHS ARE FORECAST OVER THE EASTERN CONUS AND THE BERING SEA/ALEUTIANS, WHILE A RIDGE IS ANTICIPATED OVER THE PACIFIC NORTHWEST, EXTENDING NORTH-NORTHWESTWARD OVER WESTERN CANADA AND CENTRAL AND EASTERN ALASKA. A MOSTLY ZONAL FLOW PATTERN IS EXPECTED ACROSS THE SOUTHERN TIER OF THE CONUS. THE ENSEMBLE SPAGHETTI CHARTS CONTINUE TO INDICATE MODERATE TO LARGE SPREAD ACROSS MOST OF THE FORECAST DOMAIN. TODAY'S WEEK-2 BLENDED 500-HPA HEIGHT CHART INDICATES NEAR TO BELOW NORMAL HEIGHTS OVER THE EASTERN TWO-THIRDS OF THE CONUS AND ALASKA, AND NEAR TO ABOVE NORMAL HEIGHTS OVER THE WESTERN THIRD OF THE CONUS AND THE ALASKA PANHANDLE.

DUE TO THE ANTICIPATION OF A PROGRESSIVE CIRCULATION PATTERN, THE EXPECTED AREAS OF TEMPERATURE AND PRECIPITATION ANOMALIES FOR WEEK-2 ARE QUITE SIMILAR TO THOSE FORECAST FOR THE 6-10 DAY PERIOD EXCEPT DISPLACED EASTWARD. A WETTER PATTERN IS FORECAST FOR PARTS OF THE NORTHERN PLAINS DURING WEEK 2 AS SHORTWAVE ENERGY RIDES OVER THE TOP OF THE RIDGE PREDICTED OVER WESTERN NORTH AMERICA.

FORECAST CONFIDENCE FOR THE 8-14 DAY PERIOD IS: ABOUT AVERAGE, 3 OUT OF 5, DUE TO FAIRLY GOOD AGREEMENT AMONG THE ENSEMBLE MEAN SOLUTIONS OFFSET BY MODERATE TO LARGE SPREAD AMONG INDIVIDUAL ENSEMBLE MEMBERS.   

THE NEXT SET OF LONG-LEAD MONTHLY AND SEASONAL OUTLOOKS WILL BE RELEASED ON MAY 18

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.

Day

ENSO

Phase

PDO AMO

Other Comments

Apr 22, 1951 Neutral - + In between a La Nina and subsequent El Nino
May 1, 1974 La Nina - -  
Apr 15, 1981 Neutral + -  
Apr 23, 1993 Neutral + -  
Apr 24, 1993 Neutral + -  
Apr 4, 1994 Neutral + -  
Apr 12, 2000 La Nina - + Following the 97/98 MegaNino
May 1, 2009 Neutral - + Prior to an El Nino Modoki Type II
May 2, 2009 Neutral - + Prior to an El Nino Modoki Type II

 

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

One thing that jumped out at me right away was the spread among the analogs from April 12 to May 2 which is 20 days which is a very tight spread. 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 April 22. These analogs are centered on 3 days and 4 days ago (April 20 or April 21). So the analogs could be considered to be right in sync with the calendar meaning that we will be getting weather that we would normally get at this point in the calendar.

For more information on Analogs see discussion in the GEI Weather Page Glossary.

There are seven ENSO Neutral Analogs, zero El Nino Analogs, and two La Nina analogs. Looks like the analogs are signaling ENSO Neutral for the next couple of weeks. The phases of the ocean cycles of the analogs point to McCabe Conditions A and D which are opposites. I think the explanation is that the rapid progression of systems right now results in McCabe Condition A type weather early in the forecast and McCabe Condition D type weather later in the forecast. I do not present the analogs because I think they are superior to the current dynamical models as they are not. But I believe that we can learn a lot by studying how forecasts and actuals agree or disagree with the analogs and the McCabe analysis of the condition of the PDO and AMO associated with those analogs. So this is a long term research project that I am conducting and which I share with my readers each week.

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.

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 April 15, 2017

April 15,  2017  30 Day temperature and precipitation departures.

The Precipitation pattern has not changed much. The Temperature Pattern has expand the warm results to the east and especial the Great Lakes Area.  Remember seven recent days are added and seven more distant days are removed so a 30 day average changes slowly.

And the 30 Days ending April 22, 2017

April 22, 2017 30 Day Temperature and Precipitation Departures

Looks like the North Central drought has moderated. The warm temperature anomalies have moderated also. Remember this is a 30 day average and seven more recent days have been added and seven more distant days are removed.

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 what 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 at the end of April right now so we are 2/3rds between the two set of positions shown above for January and July.

Todays Forecast

Temperature at 2 Meters

Notice that below the map there is a tabulation of magnitude of the current anomalies by region. it is warm everywhere.

Maine Reanalyer

This graphic is actuals not anomalies. We again see the wet area pretty much just south of the Equator. There is a lot of dry area including from Northern Africa to India and even into China which impacts a large number of people. There is not much that is wet in the Northern Hemisphere.

Additional Maps showing different weather variables can be found here.

Near Term (Currently Set for Day 3 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 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.

Although I can not display the interactive control panel in my article, I can display any of the graphics it provides so below are the current worldwide precipitation and temperature forecasts for three days out. They will auto-update and be current for Day 3 whenever you view them. If you want the forecast for a different day Click Here

Precipitation

BOM World Preciptation  Wednesday

Notice than Northern South American remains wet.

Temperature

BOM Current Temperature Wedensday

As for many weeks, Northern Africa, The Arabian Peninsula, and India and are projected to be very warm. The west coast of South America looks cool.

Looking Out a Few Months

Here is the new precipitation forecast from Queensland Australia:

Rising  SOI  forecast for April to June 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 the rising SOI. It is a big change.  .

JAMSTEC Forecasts

Last month, JAMSTEC issued their ENSO forecasts and climate maps on March 15. We published a special Update Report on Saturday Night March 18 which can be accessed by clicking 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. 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. We will be publishing an Update on April 20 of the new JAMSTEC and NOAA seasonal outlooks.

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
Black Sea and Caspian Sea cool. Western Mediterranean warm. Cool except west of Japan and east of Siberia in Bering Sea Warm in places. Warm but just along the coast and some cool spots to the north. Western Gulf of Mexico warm. Less warm than recently
The Tropical Pacific

Neutral with warmish bias especially just south of the Equator but cool to the east.

Africa West of Australia South and East of Australia West of South America East of South America
Warm of Northwest Africa, cool off West Africa, cool south and east of Africa Slightly cool west and southwest slightly warm Southeast Warm south of 20S. Warm south of 30S near the coast.

 

What you see in the below graphic is the change in the anomaly over the last four weeks. So blue means either cooler or less warm. Red means warmer or less cool. So you have to refer to the graphic above this one to really interpret this graphic as what we are seeing here is the change in the anomalies. It is a bit like the graphic above is the first derivative of the sea surface temperature (SST) and the graphic below is the second derivative of the sea surface temperature(SST) but not exactly. Derivatives are the rate of change and what we have here in the above graphic is the delta between the current temperature and normal temperature and then in the graphic below we have the four-week change in the delta. It is a bit similar to derivatives where the first derivative is the rate of change and the second is the rate of acceleration of the change.

April 24, 2017 four week change is SST Anomalies

The categorization of the four week change in the anomalies.

Mediterranean, Black Sea and Caspian Sea Western Pacific West of North America East of North America North Atlantic
Eastern Mediterranean  warming Slight Cooling around  Japan and east of Kamchatka Warming off of Alaska Panhandle and Cooling off of Baja Warming Warming off of NW Africa and Spain
The.Tropical Pacific Cooling west, cooling east, Warming in Nino Measurement Area
Africa West of Australia South and East of Australia West of South America East of South America
Warming off Northwest coast. Slight warming  south. and east but cooling Northeast of Madagascar. Cooling in the north. Warming off Northwest Cooling east. But warming north,south and east of New Zealand Cooling near Equator but warming south Warming off of Argentina

 

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 +0.12 +0.23  0.0
February +0.04 +0.23 +0.2
March +0.08 +0.18  0.0

 

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 April 24 for what is shown as Week Two, the period April 26, 2017 to May 2, 2017, we see dry conditions* for Venezuela, Southern California, Southeast Asia and wet conditions* for Sumatra and Somalia.
* 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.Also you can see the break in the action of Pacific Storms headed east.  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.

Notice in the top graphic the big difference between temperatures south of the Equator and north of the Equator. This creates a dynamic situation.

Current SST and wind anomalies

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

 

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)

WARM POOL

WARM POOL

0

0

+0.5C to +1C (marginal)

138W

LAND

43

18

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

WARM POOL

138W

Inf

32

0C or cooler Anomaly (coolish neutral)

LAND

LAND

0

0

 

* A water anomaly exceeding +1C is showing along the Equator in today's TAO/TRITON Five-Day Mean Graphic. I did not record that in the above table as the graphic only shows the information to 120W. The top graphic (in the pair) which I do not usually discuss suggests that this warm water remains south of the Equator. It is difficult to convert the raw data in the top graphic in the pair into the anomalies shown in the lower graphic because I do not have the conversion information by grid and it varies by grid and seasonally. The ability to convert actual temperatures to temperature anomalies would be needed to sort out the situation when the demarcation lines are so close to and parallel to the Equator. It is not that important and probably will become clear very shortly.

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 April 24, in the afternoon working from the April 23 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 +0.2 +0.4
B. 160W to 150W +0.4 +0.4
C. 150W to 140W +0.4 +0.5
D. 140W to 130W +0.6 +1.0
E. 130W to 120W +0.5 +1.3
Total +2.1 +3.6
Total divided by five i.e. the Daily Nino 3.4 Index (+2.1)/5 = +0.4 (+3.6)/5 = +0.7

 

My estimate of the daily Nino 3.4 SST anomaly tonight is +0.7 which is an El Nino value. NOAA has reported the weekly Nino 3.4 to be a marginal El Nino value at +0.5. The disparity between surface temperatures north of the Equator and south of the Equator is striking and from a measurement perspective slight changes in wind and currents can move cooler or warmer into the Nino 3.4 Measurement Area and impact the numbers reported without really having a big impact on the actual situation. 
Nino 4.0 is reported higher than last week at 0.3. Nino 3 is slight lower than last week at 0.6. Nino 1 + 2 which extends from the Equator south rather than being centered on the Equator is reported much higher at +1.1 I believe it was up there close to 3 at one time so this index has been fluctuation quite a bit.
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 table form but going back a couple of more years can be found here.

April 24, 2017 Nino Readings

This is probably the best place to 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.

This graphic  may be confusing re another one I will soon show but it indicates that actually when integrating surface and heat anomalies you end up now with a zero anomaly. I am not sure  if this is just the Equator or how far north and south of the Equator it goes but it suggest that we really are in a Neutral situation. 

April 24, 2017 Central and Western Pacific Upper 300 Meter Heat Anomala

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.

April 24, 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.
You can see that the cool anomaly (bottom of the Hovmoeller has vanished with no blue in the Nino 3.4 Measurement Area), some white and now quite a bit of light yellow (still ENSO Neutral but on the warm side) and El Nino-ish dark yellows off and on from 160W east and browns from 110W east but the reds are no longer showing at the bottom of the chart. Whether it is expansion from the west or the east the bottom of the Hovmoeller is now light yellow which is not El Nino warm but clearly on the warm side of Neutral so that is a big change week to week. 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 is possibly the beginning of an El Nino pattern. But week to week there have been no substantial change. If anything the pattern is fairly stable. Basically there is on balance no change from last week.
I had stopped showing the below graphic which is more focused on the Equator but looks down to 300 meters rather than just being the surface. But recently there has been sufficient change to warrant including this graphic. And now that we are back tracking a possible El Nino it is the graphic of choice.

April 24, 2017 Upper Ocean Heat Anoma

The bottom of the Hovmoeller shows the current situation. The Cool Event is long gone. But what might be successive Kevin waves initiating an El Nino are still not very impressive. If you look from the bottom of the graphic up you can see that any La Nina conditions ended in December. There is not much change from the prior week but a cooler area is no longer in the picture.  But what I am really looking for is the left portion of the graphic the Pacific Warm Pool and I don't see much change. Reds are what is needed for an El Nino. There could be another weak Kelvin Wave getting started but we will need a couple of weeks to see if that is the case. So far there is no indication of this but not shown in this report the overall pattern of Easterlies has declined a bit so there is a bit more opportunity for a Kelvin Wave to get started. So far the change has been small.

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). 

.April 24, 2017 Kelvin Wave Analysis.

Usually we use this to track Kelvin Waves but you can see the progression of warm water streaming east but not very much of it. Hard to conclude that warm water is moving subsurface to the East with that blue cool blob 155W to 135W with a smaller one further east. . The reason this is important is what is called the Bjerknes Feedback Mechanism which you can read about here. It is an intricate set of interactions which determines the ENSO Cycle. Of course Jacob Bjerknes the son of the world renowned Norwegian meteorologist Vilhelm Bjerknes developed his theories in the sixties. There have been many modifications/improvements in his theories since then and this process continues. You can track the history of this graphic on the right. I think it shows the prior week and then every other week before then. There has not been much change. There is no indication of an El Nino forming. There is no real warm water flow from the Indo-Pacific Warm Pool to the Eastern Pacific. But the surface is just a bit warmer.

Now for a more detailed look. Notice by the date of the graphic (dated April 18, 2017) that the lag in getting this information posted so the current situation may be a bit different than shown. 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 but for different purposes.

Subsurface Heat Anomalies

Re the top graphic, let us first look at surface temperature anomalies. The -1C and -0.5C water no longer shows anywhere except for a few degrees of -0.5C water at about 170W. On the other hand, warm water continues to extend from the Coast of Ecuador to 110W and slightly warm water all the way to 130W. Subsurface Temperature Anomalies: The cool water is almost all gone. Notice the warm water at depth but there is a big gap between the 170W and 115W. There has been hardly and change during the last two reports which are each approximately five days apart. So there is basically no change from last week.

The bottom half of the graphic (Absolute Values which highlights the Thermocline) is now more useful as we track the transition to an ENSO Cool Event which may possibly become an El Nino.

It shows the thermocline between warm and cool water. The 28C Isotherm is now located at the Dateline. This graphic does not show a 27.5C anomaly which might more precisely indicate where convection is likely to occur. The 27C isotherm is at 160W. So there may have been 5 more degrees of movement to the east since last week. We do not yet have ideal (El Nino) conditions for significant convection along the Equator east of the Dateline. What we have is increasingly looking like ENSO Neutral but on the fringe of minimal El Nino levels. The 25C isotherm now extends all to the way to Ecuador but it is getting closer to the surface. The 20C Isotherm is depressed by warm water all the way to Ecuador. We are seeing the great swap where neutral and even warm water replaces the cooler water at the surface. But this process seems to be pretty much stalled or happening very slowly at this point in time.
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 but not El Nino.

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

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

OLR Anomalies Along the Equator

There is not much week to week change in the pattern.

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 April 24 was reported as -6.04 which is ENSO Neutral but getting close to an El Nino value. The 90 Day Average was reported at -1.35 which is ENSO Neutral. Looking at both the 30 and 90 day averages is useful and both are in agreement that we are in ENSO Neutral but trending towards El Nino..

 

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 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

We now have both the early April (April 13) and Mid-April (April 20) reports from CPC/IRI  I am showing both as it is a way of seeing the trend in forecasts even though the methodology of the two forecasts are not identical.

April 20, 2017 CPC/IRI Update two graphics side by side.

First we look at graphic on the left which is the IRI/CPC what I call the "Tea Leaves Report" issued on April 13, 2017. I call it the Tea Leaves Report as it is not clear how this report is prepared as it is some combination of model results and opinions of meteorologists and it is just not possible to really know how this report is prepared. Then we look on the right at the most recent (April 20) Model Based report. Notice the new report has much higher and sooner probabilities for El Nino than the prior report.

Here click to read is the discussion that was issued with the April 20 Report.e human judgment in combination with the model guidance.

Here is the daily PDF and Spread Corrected version of the NOAA CFSv2 Forecast Model.

CFSv2 spread and bias correct ENSO forecast

The estimated current value of the Nino 3.4 Temperature Anomaly after the adjustments have been applied is an ENSO Neutral Value now with a warm bias and shooting higher fairly rapidly this month. Looking ahead to next summer you see El Nino readings being the mean of the forecast ensemble but this forecast is still before the Spring Prediction Barrier which means we need to wait until May [click here to understand why] before getting excited about that. Notice the wide spread among forecast member into the summer. The forecasts have come down from a strong El Nino to what may be barely an El Nino if at all. We discussed that recently in this article - click to read.

The full list of weekly values can be found here.

From Tropical Tidbits.com

CDAS Legacy System

The above is from a legacy "frozen" NOAA system meaning the software is maintained but not updated. It seems to show a cycle in the Nino 3.4 Index Values. I see that as I monitor the TAO/TRITON graphic. My best guess is that it is related to the MJO but it certainly is intriguing. I do not need to draw in the lines for you to see that the Nino 3.4 Index as reported by CDAS has moved above the 0C line and is now reporting a warm anomaly but not yet an increasing warm anomaly.

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 (notice their threshold criteria are different from NOAA). Also the seasons in the Southern Hemisphere are the reverse of those in the Northern Hemisphere.

ENSO neutral, but tropical Pacific waters continue to warm

The El Niño–Southern Oscillation (ENSO) remains neutral. However the Bureau's ENSO Outlook is currently at El Niño WATCH, meaning there is around a 50% chance—twice the normal likelihood—of El Niño developing in 2017.

Tropical Pacific sea surface temperatures (SSTs) have warmed since the start of the year. SSTs in the central tropical Pacific are now 0.5 °C warmer than average, still below the +0.8 °C threshold for El Niño levels. Atmospheric indicators of ENSO remain firmly neutral, although the Southern Oscillation Index (SOI) has returned to negative values over the past fortnight.

International climate models suggest the tropical Pacific Ocean is likely to continue warming in the coming months, though in recent weeks some models have reduced the expected extent of warming. Five of eight models indicate that sea surface temperatures will exceed El Niño thresholds during the second half of 2017; a reduction of two models since the last Wrap-Up release. It should be noted that models have lower accuracy at this time of year.

El Niño is often, but not always, associated with below average winter–spring rainfall over eastern Australia. Of the 27 El Niño events since 1900, 18 resulted in widespread dry conditions for parts of Australia.

The Indian Ocean Dipole (IOD) is currently neutral.. Four out of six climate models suggest a positive IOD is likely during winter. When a positive IOD coincides with El Niño, the typical El Niño dry signal expands, and generally stretches further west over eastern and central Australia.

Here is the recently released JAMSTEC forecast of the Nino 3.4 values which are the most looked at index used to forecast El Nino.

JAMSTEC April 1, 2017 ENSO Forecast.

The Discussion that goes with their Nino 3.4 forecast has just been released so here it is:

Apr. 18, 2017

Prediction from 1st Apr., 2017

ENSO forecast:

The SINTEX-F predicts that a moderate-to-strong El Niño event may start in late spring this year and reach its peak in winter. This probability is enhanced and we expect negative sea level anomalies in Micronesia and Melanesia. The frequent occurrences of El Niños in recent years suggest a decadal turnabout in the tropical Pacific climate condition to El Niño-like state after a long spell of La Niña-like state. Such natural climate variability may double the global warming impact as we observed during the period from 1976 through 1998. We need to be prepared well to this possible decadal climate regime shift.

Indian Ocean forecast:

Occurrence of a positive Indian Ocean Dipole is also clearly predicted by the SINTEX-F seasonal prediction system; the ensemble mean prediction suggests its evolution from late spring and its peak in fall. In accord to the positive IOD evolution, sea level anomalies are expected to be negative (positive) in the eastern (western) tropical Indian Ocean. We may observe co-occurrence of a positive Indian Ocean Dipole and an El Niño in the latter half of 2017; this is just as we observed in 1997 and 2015.

Regional forecast:

On a seasonal scale, most part of the globe will experience a warmer-than-normal condition, while some parts of southeastern Russia and northern Australia will experience a colder-than-normal condition in the boreal summer. In the boreal fall, most part of the globe also will be in a warmer-than-normal condition, while some parts of southern and eastern Russia and Somalia will be in a colder-than-normal condition in the boreal fall.

As regards to the seasonally averaged rainfall, a wetter-than-normal condition is predicted for most parts of Southeast Asia, Philippines, the Far East, and West Africa during the boreal summer, whereas most parts of Indonesia, Australia, India, eastern China, and northern Brazil will experience a drier condition during the boreal summer. In the boreal fall, most parts of Indonesia, Philippines, northern India, Australia, Mexico, southern Brazil and Europe will experience a drier-than-normal condition. Those are partly due to co-occurrence of the El Niño and the positive Indian Ocean Dipole. In particular, the drier condition in Indonesia and Australia will be augmented by the co-occurrence.

Most parts of Japan will be moderately warmer-than-normal and wetter-than normal in summer. In particular, we expect more rain in the western Japan in the Baiu season. In contrast, we expect a drier condition in fall. El Niño influences may be canceled regionally owing to development of the positive Indian Ocean Dipole and vice versa.

On Saturday April 22 we will be releasing our analysis of the NOAA and JAMSTEC seasonal outlook updates. I already have the JAMSTEC information and will receive the NOAA information on Thursday April 20

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

Indian Ocean Dipole outlooks  [Editor's Note: Remember the Seasons are reversed in the Southern Hemisphere as compared to the Northern Hemisphere]

The Indian Ocean Dipole (IOD) is neutral. The weekly index value to 23 April was +0.2 °C

The northern Australian wet season is nearing its end. This means the IOD may start to influence the Australian climate. When the monsoon trough and associated wind patterns are located in the southern hemisphere, an IOD circulation is unable to develop. Therefore, the IOD has little influence on Australian climate from December to April.

Current outlooks suggest a neutral IOD for the end of autumn, with some models indicating a positive IOD may form later in winter or spring.

D. Putting it all Together.

At this time there is now interest as to whether or not this Summer and Fall will be El Nino situations. The models are suggesting this as a possibility. But it is too soon to tell due to the Spring Predictability Barrier or SPB which is was explained at this link.

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.

JAMSTEC has raised the possibility of a Climate Shift in the Pacific and the implications of this are discussed in a prior GEI Weather and Climate Report which you can access by clicking here.

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. Parts of that discussion are in the beginning  section of this week's Report.

The odds of a climate shift for CONUS taking place has significantly increased. It may be in progress.  JAMSTEC is suggesting that if there is an El Nino in the winter of 2017/2018 this could signify that the PDO has entered its Positive Phase. 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. JAMSTEC is suggesting it might occur very soon.

E. Relevant Recent Articles and Reports

Weather in the News

Hint of Early Start to Atlantic Hurricane Season.

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 April 10, 2017

The Jan/Feb/Mar preliminary has just come out as -0.2. The full history of the ONI readings can be found here. The MEI index readings can be found here.

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

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