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posted on 20 November 2017

November 20, 2017 Weather and Climate Report - Southwest Roasts

Written by Sig Silber

Some Southwest States may set high temperature records on Thanksgiving Day and the Phoenix Airport may record the first Meteorological Fall Season without measurable precipitation since 1938. Alaska is getting back-door cold fronts which are creating Gulf of Alaska Lows which then provide moisture to the Northwest. La Nina and Global Warming result in interesting weather. Continue reading to learn more. 

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Some housekeeping: Last Monday, November 13, 2017, the late night edition of my article mistakenly referenced an older post by Emily Becker and I did not notice that and apologize for any confusion. But this is the correct version of her post which you can read in full here..  Also on Saturday November 18, 2018 we published our monthly Seasonal Outlook Update and you can access that here. Remember if you leave this page, to get back you need to hit the return arrow usually located on the left of your URL box on the upper left of the screen.

From Sunday's NWS Phoenix Office Discussion and repeated again today Monday in the morning but this evening they may be walking it back a bit from the prior 89F forecast with 90F as possible as the current forecast is for only 88F.

Latest blended guidance continues to strongly suggest that temperatures will exceed daily records by Wednesday and Thanksgiving (see climate section below). Given the exceptionally low Standard deviations evident in the European model (ecmwf) temperature guidance, the official  forecast was adjusted above the median of all available guidance resulting in a forecast high of 89 degrees for Phoenix Thanksgiving day. It's not totally out of the question that Phoenix could flirt with 90 degrees Wednesday/Thursday, which would set a record for the latest 90 at kphx (record is 90 deg on Nov 15 1999). Pops also remain at 0 percent and it is very likely the long dry stretch will continue into at least the end of November, which would result in a meteorological fall (sept-Oct-nov) without any measurable rainfall at Sky Harbor Airport (last occurred in 1938).

Climate...record highs for selected dates this week:

Date......... Phoenix ........Yuma

Nov 21 88 in 1924....... 90 in 1950

Nov 22 89 in 1950....... 91 in 1950

Nov 23 87 in 1950....... 87 in 1950

Nov 24 88 in 1950....... 89 in 1950

Nov 25 88 in 1950....... 90 in 1950

Nov 26 87 in 2014....... 87 in 1950

The Phoenix record high for any Thanksgiving is 87 on Nov 23 1950 and Nov 27 2014. The Yuma record high for any Thanksgiving is 87 on Nov 23 1950.

Most days of 80+ during November in phoenix: 24 in 1949.

Most days of 80+ during November in yuma: 24 in 1954, 1950, and 1949.

Latest 90+ day in phoenix: Nov 15 (1999)

latest 90+ day in yuma: Nov 25 (1950)


Some of this is discussed in this report and more was discussed Saturday Night in our Monthly Seasonal Outlook Update which you can access here.

A. Now we focus on Alaska and CONUS (all U.S.. except Hawaii)

I am starting with a summary of small images of the three short-term maps first for temperature and then for precipitation 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. Later in the article for those with sufficient interest, you can find the larger maps and a discussion and for reference purposes I then also provide the forecast map for the current or soon to be current full month and the three-month forecast map. These are issued and updated less frequently than the first three maps shown.

There is also a full description of the factors determining the maps shown next and a detailed analysis of the ENSO situation which so dramatically impacts the forecasts below.

First Temperature

6 - 10 Day Forecast Temperature

Transitioning from the 6 to 10 day outlook on the left to the 8 to 14 day outlook on the right         →

8 - 14 Day Temperature

Zonal shift to the east.

To the right is the week 3 and 4 Forecast.

There are now two warm anomalies and no cool  anomalies. →

3 - 4 Week Temperature


←  The transition from the 8 -14 day forecast shown above to the week 3/4 shown to the left seems feasible. But recent model runs reduce the confidence in forecasts beyond Day 7.


And then Precipitation

6 - 10 Day Forecast Precipitation Transitioning from the 6 to 10 day outlook on the left to the 8 to 14 day outlook on the right.         → 8 - 14 Day Precipitation

Zonal flow the east.

To the right is the week 3 and 4 Experimental Forecast.          →

Notice the large dry anomaly.

 3 - 4 Week Precipitation


←  The transition from the 8 -14 day forecast shown above  to the week 3/4 shown to the left seems to be feasible. But recent model runs reduce the confidence in forecasts beyond Day 7.


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

You can see the moisture streaming into the Northwest.  Remember this is an animation of what has happened not a forecast. 

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 November 20, 2017, as I am looking at the above graphic, you see the water vapor over the Northwest and then having moved up into the Great Lakes Area. 

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 two branches of the Jet Steam  merging. I think these are both branches of the Polar Jet stream. The northern branch went over or North of Alaska and then doubled back into the  Gulf of Alaska.

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

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

You can see the moisture entering the Northwest.

Day One CONUS Forecast

Day 1 Forecast Map

Day Two CONUS Forecast

Day 2 Forecast

You can see snow forecast for the Northwest. And you also see the High keeping the Southwest unusually warm for this time of the year.

60 Hour Forecast Animation

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

current highs and lows

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

Tropical Activity

Eastern Pacific Two Day Tropical Weather Outlook

When there is activity and I have not provided the specific links to the storm of "immediate" interest, one can obtain that information at this link. At this point in time, no (new) tropical events are expected to appear in this graphic during the next 48 hours. If that changes, we will provide an update.  .

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.

Day 7 Highs and Lows

When I look at this Day 7 forecast, there is a LOW over Kamchatka with surface central pressure of 988 hPa.  And you can also see a weak Low off of British Columbia with surface central pressure of 1000 hPa. And there is a High somewhere out to sea with surface central pressure of 1020 hPa. There is also a High over the Rocky Mountains with surface central pressure of 1020. This is a good set up for moisture to enter CONUS fairly far south. There is also a Low over New England with surface central pressure of 992 hPa. They probably will be getting some snow.

I provided this K - 12 write up that provides a simple explanation on the importance of semipermanent Highs and Lows and another link that discussed possible changes in the patterns of these highs and lows which could be related to a Climate Shift (cycle) in the Pacific or Global Warming. Remember this is a forecast for Day 6. It is not the current situation.

The table below showing the Day 3, 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.

Day 3 Day 6

From left to right and then down, these are small images but you can see  a fairly stable situation in the Gulf of Alaska. The graphics update but my commentary does not so it is just a guide for how to read these graphics.

Day 7


Now looking at the Day 5 Jet Stream Forecast by one weather forecasting model.

Jet Stream Five Days Out .

You can again see both the Polar Jet Stream. It appears to be mostly zonal flow across CONUS. There is a weak trough impacting the Great Lakes on Day 5 and also a Western Ridge. So it is not exactly zonal flow: perhaps quasi-zonal flow. .

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

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

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

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

air pressure and altitude

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

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

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

Short term forecasts

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

Seven Day WPC Quantitative precipitation forecast

We see a wet Northwest. We also see a large area of zero 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 generally signifies equal chances for snow at sea level locations. Thickness of 600 or more suggests very intensely heat and fire danger. Thinking about clockwise movements around High Pressure Systems and counter- clockwise movements around Low Pressure Systems provides a lot of information.

7 Day 500 MB Geopotential Forecast

What we see for Day 7 is the Western Ridge and a Northeast Trough with thickness levels suggestive of snow. We also see that High over Mexico which may be a result of La Nina or separate from La Nina but either way is part of keeping the pattern to the north.
Note the 540 Thickness Line re the above discussion of thickness and snow likelihood. We are this week again down to 540 so areas north of this snowline have a good chance to have snow in valleys not just mountains.  And that might mean for Day 7 possibly a major snow event for the Northeast. Thickness lines near or over 600 (which we generally do not have this time of the year) tend to suggest very warm temperatures. Sometimes Meteorologists work with the 500 mb heights which provide somewhat similar readings to the "Thickness" lines but IMO provide slightly less specific information.

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

6 - 10 Day Temperature Outlook issued today (Note the NOAA Level of Confidence in the Forecast Released on November 20, 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 November 20, 2017 was 2 out of 5).

8-14 Day Temperature Outlook

Looking further out.

Experimental Week 3-4 Temperature Outlook

Reference Forecasts Full Month and Three Months.

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

December Temperature Early Outlook Issued on November 16, 2017

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

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

DJF 2017 - 2018 Temperature Outlook Issued on November 16, 2017

Now - Precipitation

6 - 10 Day Precipitation Outlook Issued Today (Note the NOAA Level of Confidence in the Forecast Released on November 20 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 November 20, 2017 was 2 out of 5)

Current 8 - 14 Day Precipitation Outlook

Looking further out.

Weeks 3 and 4 Experimental Forecast..

Reference Forecasts Full Month and Three Months.

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

December 2017 Precipitation Outlook Issued on November 16, 2017

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

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

DJF 2017-2018 Precipitation Outlook Issued on November 16,  2017

Here is the 6 - 14 Day NOAA discussion released today November 20, 2017 and the  Week 3/4 discussion released Friday November 17, 2017

6-10 DAY OUTLOOK FOR NOV 26 - 30 2017  





8-14 DAY OUTLOOK FOR NOV 28 - DEC 04, 2017  





Week 3-4 Forecast Discussion Valid Sat Dec 02 2017-Fri Dec 15 2017

The Week 3-4 outlook this week takes place within a backdrop of ongoing La Nina conditions and after the demise of a rather substantial MJO event during October into November. La Nina ocean and atmospheric conditions serve as the low frequency base state for this outlook with no predictions of revitalized, organized MJO activity anticipated over the next 1-2 weeks. The forecast temperature and precipitation outlooks are based on low frequency La Nina background conditions, in some areas local sea surface temperature anomalies, statistical model guidance and long term trends. Dynamical model guidance also played a substantial role in the outlooks, but primarily from the ECMWF system.

The dynamical model guidance had large spread this week with all three utilized operational center model systems offering varying depictions of some of the large scale features over the Pacific Ocean and North America region. There were large changes in Week-3 forecasts from the CFS and JMA solutions across the Pacific sector than that most likely to arise out of the Week-2 period at the moment. It was viewed that the ECMWF solution for Week-3 to be the most consistent and representative with the anticipated eventual evolution over the Week 2-4 time period. Therefore, its temperature and precipitation forecast was considerably more heavily weighted in the final outlook maps.

The temperature outlook depicts elevated probabilities for above normal temperatures for northern and western areas of Alaska supported by continuing above normal sea surface temperatures, long term trends and the majority of bias corrected, calibrated dynamical model guidance. Statistical model forecast guidance incorporating information from ENSO, the MJO and long term trends favors above normal temperatures for areas across the southwest corner of the CONUS with the primary drivers being La Nina and long term trends, rather than the MJO. Dynamical model guidance especially from the ECMWF and JMA further support this area of elevated odds of anomalous warmth so probabilities are highest in this region. The enhanced likelihood of above normal temperatures extends to the north to include much of the remainder of the West as well as much of the Great Plains. This is supported by the expectation of considerable Pacific air entering the CONUS consistent with the preferred ECMWF solution and so its calibrated dynamical model guidance, but also to a lesser degree from the CFS and JMA solutions. The probabilities are lessened for the northern Plains in deference to statistical model guidance favoring below normal temperatures related to a potential La Nina influence. There exists considerable uncertainty in both statistical and dynamical model guidance across the eastern CONUS as even model output from the ECMWF is quite muted as well as in contradiction to solutions from the CFS and JMA systems. Equal chances (EC) is forecast in the eastern CONUS.

The precipitation outlook utilized a mixture of statistical model forecast guidance, some commonly observed La Nina impacts and bias corrected, calibrated dynamical model guidance. Even though at odds with typical La Nina impacts, above normal precipitation is favored for parts of the South Coast of Alaska and the Alaska Panhandle as the preferred dynamical model guidance (i.e., ECMWF), supports wetter than normal conditions in this region. The North Slope of Alaska also has an enhanced likelihood of above normal precipitation as indicated by all bias corrected, calibrated dynamical model guidance. The strong trough and somewhat zonal flow across the Pacific to the West coast of North America predicted by the ECMWF solution favors above normal precipitation for areas of the Pacific Northwest. Statistical model guidance (mainly from long term trends) favors an extension of this area to the east to include parts of the northern Rockies. A rather large area of marginally elevated probabilities for below normal precipitation is shown from the Southwest CONUS, east and north to include much of the interior portion of the country, to the Gulf Coast and Florida. A combination of factors, the La Nina low frequency base state, long term trends and the anticipated upper-level height pattern (ridge-trough) over the period across the CONUS favors in the mean an area of upper-level convergence and so generally fair surface conditions.

For Hawaii, above normal ocean surface temperatures favor elevated odds for above normal temperatures for all areas. Dynamical model guidance quite marginally favors above normal precipitation for eastern areas of the Hawaiian Islands while uncertainty in the forecast tools results in an outlook of EC for western areas.

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.






Other Comments

Dec 2, 1954 La Nina -(t) -  
Dec 3, 1954 La Nina -(t) -  
Nov 21, 1970 La Nina - -  
Nov 22, 1970 La Nina - -  
Nov 26, 1970 La Nina - -  
Nov 6, 1971 La Nina - -  
Nov 7, 1971 La Nina - -  
Nov 10, 1973 La Nina - -  
Nov 23, 1990 Neutral - -(t)  
Nov 5, 1996 Neutral N -  

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

The spread among the analogs from November 5 to December 3 is 28 days which is twice the spread of the prior 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, is about November 19. These analogs are centered on 3 days and 4 days ago (November 17 or November 18). So the analogs could be considered to be in sync with respect to weather that we would normally be getting right now. For more information on Analogs see discussion in the GEI Weather Page Glossary.

There were no duplicate analogs this week. There are two Neutral Analogs, eight La Nina analogs and zero El Nino Analogs. The phases of the ocean cycles of the analogs are very consistent with McCabe Condition B which itself is consistent with the 6 - 14 Day forecast except that the pattern is further north than what we would expect with McCabe Condition B which is why I am not surprised that some of the models are suggesting that the pattern may turn out to be a bit further south than the current forecast. .

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

McCabe Maps modified to include the subtitles

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

McCabe Conditions from 2007 report with labels corrected with authors permission

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

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

Looking Out Beyond Three Months

On Saturday November 18, we published our Three to Four Season Outlook and compared the forecasts of NOAA and JAMSTEC for the first three seasons namely Fall, Winter, and Spring. This report can be accessed here. There will be a new Seasonal Outlook issued by NOAA on December 21 which we will report on December 23.

Historical Anomaly Analysis

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

Recent CONUS Weather

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

Here is the 30 Days ending November 11, 2017

Novermber 11, 2017 30 Day Temperature and Precipitation Departures

Not much change in the precipitation pattern but you sure can see the cooler Northern Tier west of Minnesota. Remember, this is a 30 average so the most distant seven days are removed and the most recent seven days are added.

And the 30 Days ending November 18, 2017

November 18, 2017 30 Day Temperature and Precipitation Departures

The precipitation record is pretty much unchanged. The temperature situation is changed especially for New England and the Northern Tier cool anomaly is shown further east.  Remember, this is a 30 average so the most distant seven days are removed and the most recent seven days are added.

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

Same as above but for July

I will be including the above two graphics regularly as they really help with understanding why things are happening the way they are. I think the (at least intermediate) Source is The Weather Channel and I was able to download the full presentation with difficulty and you can attempt the same thing by clicking here. I think these two graphics 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 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 the end of November so we are 5/6ths between the set of positions shown above for July and the ones shown for January. For CONUS, the seasonal repositioning of the Bermuda High and the Pacific High are very significant. Notice the Winter position of the Pacific High. Right now it is not in the January Position or close to it.

Forecast for Today

Temperature at 2 Meters

Notice that below the map there is a tabulation of magnitude of the current anomalies by region. Overall it is warmer than climatology. But we see some cool areas also

Maine Reanalyer

This graphic is actuals not anomalies as is the case in the temperature map. We again see the dry area from North Africa through Asia other than (a small part of) extreme Southeast Asia but including most of India. South America south of the ITCZ is mostly wet until you get south of Brazil. Africa north of the Equator and the ITCZ is mostly dry but the wet zone extends fairly far south. Australia is mostly dry. Southern Europe is wet.

Additional Maps showing different weather variables can be found here.

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

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


BOM Current Temperature Wedensday

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


BOM World Preciptation  Wednesday

.I do not see much of interest for the Northern Hemisphere other than the storm off the Northeast Coast.

And now we have experimental forecasts from the US NAEFS Model.

NAEFS 8 - 14 Day Temperature

And Precipitation

NAEFS Experimental World Precipitation

Looking Out a Few Months

Here is the precipitation forecast from Queensland Australia:

Consistently positive SOI  forecast for November to January  2017.- 2018

It is kind of amazing that you can make a worldwide forecast based on just one parameter the SOI and changes in the SOI. Notice the change from the forecast last month due to a change from a consistently near zero SOI  to a consistently positive SOI. CONUS now looks like a north south divide with the northern tier wet. Southern Africa is wet. Eastern Australia is wet.

JAMSTEC Forecasts

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

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

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

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

                              First the categorization of the SST anomalies.

Mediterranean, Black Sea and Caspian Sea Western Pacific West of North America North and East of North America North Atlantic
Fairly Neutral but Caspian Sea warm..

Mixed but slightly  coolish except warm east of Kamchatka.

Slightly warm off Baja

Warm off East Coast especially to the north.

Warm north of Scandinavia,


Pacific cool east of 170E

SST Daily Anomalies
Africa West of Australia North, South and East of Australia

West of South America

East of South America

Cool of southeast coast


warm southeast.

Cool, cool, cool. Intensely cool but not right offshore of  Ecuador

Cool offshore east of 20S

Warm 30S to 40S


Then we look at the change in the anomalies.  Here it gets a little tricky as 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

Black and Caspian Seas warming. Western Mediterranean cooling.

Cooling east of Asia except between China and Japan.

Cooling west of and far to the east of Kamchatka

Slight cooling Bering Strait

Warming west of Northern California.

The changes are definitely in the direction of a more negative PDO.


Cooling Gulf of Mexico and Western Caribbean

Warming east of British Isles.  .

Equator Indian Ocean warming. Pacific mixed. Atlantic Cooling
Change in weekly anomalies November 20, 2017
Africa West of Australia North, South and East of Australia West of South America East of South America

Cooling west of North Africa but just above the Equator.

Warming south of Africa.

Intense warming but further south than last week. Coolling to the northeast.

Cooling 15S but mostly offshore

Warming south of 30S and off the Southern Cape.

Cooling 20S to 40S


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

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

AMO click for full list.

Indian Ocean Dipole (Values read off graph)
October   -0.68 +0.39 -0.3
November   +0.84 +0.40 0.0
December   +0.55 +0.34 -0.1
January   +0.10 +0.23 0.0
February   +0.04 +0.23 +0.2
March   +0.12 +0.17 +0.0
April   +0.52 +0.29 +0.2
May   +0.30 +0.32 +0.2
June   +0.19 +0.31 0.0
July   -0.50 +0.31 0.0
August   -0.68 +0.31 +0.4
September   -0.28 +0.35 +0.2
October   -0.60 +0.44  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 November 20 for what is shown as Week Two, the period November 22 to November 28, 2017, we see wet conditions (* and**)  for the Maritime Continent and wet conditions* for Panama and western Africa just south of the Equator and wet and cyclone development conditions* for Indochina and Bangladesh.

 * Moderate Confidence that the indicated anomaly will be in the upper or lower third of the historical range as indicated in the Legend. ** High Confidence that the indicated anomaly will be in the upper or lower third of the historical range as indicated in the Legend.

Now let us look at the Western Pacific in Motion.

Western Pacific Tropical Activity

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

C. Progress of ENSO

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

Starting with Surface Conditions.

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

Current SST and wind anomalies

Location Bar for Nino 3.4 Area Above and Below

------------------------------------------------ A B C D E -----------------


The pattern now is very cold water to the south of the Equator with warm water to the north of the Equator. That means ENSO Neutral.

The below table only looks at the Equator (and starting this week I am including large anomalies just off the Equator also) 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


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)





+0.5C to +1C (marginal)





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





0C or cooler Anomaly (coolish neutral)





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





-1.0C or cooler Anomaly





-1.5C or cooler Anomaly*





-2.0C or cooler Anomaly





-2.5C or cooler Anomaly






* There is a -1.5 or colder anomaly approximately 140W to 120W but it is  just  barely touching the Equator so I did not  count it but it could have been counted. Similarly there is a +0.5C or warmer anomaly just south of the Equator which stretches from 165W to 142W which also was not counted in the above analysis because it just barely touched the Equator. 

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 November 20, in the afternoon working from the November 19 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

Anomaly Segment Estimated Anomaly
  Last Week This Week
A. 170W to 160W +0.1 -0.6
B. 160W to 150W -0.1 -0.5
C. 150W to 140W -0.6 -0.8
D. 140W to 130W -0.7 -1.0
E. 130W to 120W -0.8 -1.1
Total -2.1 -4.0
Total divided by five i.e. the Daily Nino 3.4 Index (-2.1)/5 = -0.4 (-4.0)/5 = -0.8

My estimate of the daily Nino 3.4 SST anomaly tonight is -0.8 which is an ENSO La Nina value. NOAA has reported the weekly Nino 3.4 to again be -1.1 which is a fairly strong La Nina value and to us appears too high relative to the TAO/TRITON graphic. But the NOAA value is consistent with the CDAS values so it probably is correct and perhaps TAO/TRITON might be underreporting the cool anomalies. It is not that important as we get official values at the end of every three month period. Nino 4 is reported slightly cooler at -0.4. Nino 3 is slightly  warmer at -1.1. Nino 1 + 2 which extends from the Equator south rather than being centered on the Equator is reported slightly warmer at -1.0. It was up there close to 3 at one time so this index has been declining quite a bit and also fluctuating quite a bit which is not surprising as it is the area most impacted by the Upwelling off the coast. So it is an indication of the interaction between surface water and rising cool water. Thus it is subject to larger changes. 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.

The cool anomaly has shifted west this week and again records as La Nina.

Novermber 20, 2017 Nino Readings

This is probably the best place to AGAIN express the thought that this way of measuring an ENSO event leaves a lot to be desired. Only the surface interacts with the atmosphere and is able to influence weather. The subsurface tells us how long the surface will remain cool (or warm). Anomalies are deviations from "Normal". NOAA calculates and determines what is "Normal" which changes due to long ocean cycles and Global Warming. So to some extent, the system is "rigged". Hopefully it is rigged to assist in providing improved weather forecasts. But to assume that any numbers reported can be assumed to be accurate to a high level of precision is foolhardy.

This overlaps with the next topic but I will show it here.

Equatorial (0 - 300) meter heat content As reported November 13, 2017

The discussion in this slide says it better than I could. One might compare the current reading to Oct/Nov 2016. We may be at Peak La Nina  but it has a few months to run.

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.

November 20, 2017 Equatorial Pacific SST Anomalies

A major advantage of the Hovmoeller method of displaying information is that it shows the history so I do not need to show a sequence of snapshots of the conditions at different points in time. This Hovmoeller provides a good way to visually see the evolution of this ENSO event. I have decided to use the prettied-up version that comes out on Mondays rather that the version that auto-updates daily because the SST Departures on the Equator do not change rapidly and the prettied-up version is so much easier to read. The bottom of the Hovmoeller 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.

Not much changed from last week but perhaps one now sees this week more blue in the Nino 3.4 Measurement Area than least week especially in the Nino 3.4 Measurement Area. So the Nino 3.4 Index is likely to be a La Nina value this week. You can see where La Nina took a vacation but it was a short vacation.

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

November 20, 2017 Upper Ocean Heat Anoma

The bottom of the Hovmoeller shows the current situation. The pattern is shifted to the east. We see more cool anomaly east of 120W where the Nino 3.4 Index is measured suggesting the impact of the MJO being in the Active Phase.

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).

.November 20, 2017 Kelvin Wave Analysis.

Winds or currents are keeping most of the cool water just below the surface. There is cool water at depth from the 160W to LAND. The cool water is reaching the surface mostly east of 135W so only part of the cool anomaly is reaching the surface in the Nino 3.4 Measurement Area. It is less this week than last week. We also see a growing warm water anomaly extending from the west to the Dateline and now beyond to 175W..It is at depth not on the surface but it is signaling the probably end of this La Nina not to an El Nino but to ENSO Neutral but it will take a while for that warm water to arrive in the Nino 3.4 Measurement Area. BUT IT MAY HAPPEN MORE RAPIDLY THAN THE MODELS ARE SHOWING. 

Anomalies are strange. You can not really tell for sure if the blue area is colder or warmer than the water above or below. All you know is that it is cooler than usual for this time of the year. A later graphic will provide more information. Aside from buoyancy the currents tend to bring water from that depth up to the surface mostly farther east.

Now for a more detailed look. 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.

There is cold water from 170W to Land. To the west it is now not quite 200 meters deep. We now have warm water developing west of the Dateline and starting to cross the Dateline. Soon it will be intruding into the Eastern Pacific Nino 3.4 Measurement Area. La Nina's days are numbered.
Subsurface temperature Anomalies
The 28C Isotherm is at 175W, the 27C Isotherm is at 170W, the 25C Isotherm is at 145W.


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 and we have gone to a Weak La Nina thermocline.

Tracking the change.

Sepember 15, 2017 Subsurface Water Temperatures Equatorial Ocean Subsurface as of November 14, 2017


I have "frozen" these two charts. The one on the left shows the situation as reported for September 15, 2017. The one on the right shows the situation now.  The situation is not much different east of the Dateline from the situation as reported for September 15, 2017. But west of the Dateline is looks a lot different. We will use the graphic on the left as a reference and see how the current situation changes over time.

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

Equatorial Temperature Simulation

Isotherm Simulation

And now Let us look at the Atmosphere.

Low-Level Wind Anomalies near the Equator

Here are the low-level wind anomalies.

Low Level Wlind Anomalies

We now see easterly anomalies in the Nino 3.4 Measurement Area which means that the cool water below the surface will be rising to the surface as the water on the surface is blown to the west.

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

OLR Anomalies Along the Equator

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

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

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

Current SOI Readings

The 30 Day Average on November 20 was reported as  6.98 which is a marginal La Nina value. The 90 Day Average was reported at 7.99 which is also somewhat of a marginal La Nina value. Looking at both the 30 and 90 day averages is useful and right now both are in agreement with the 90 day lagging the 30 day as one would expect. But the decline in the 90 Day average needs to be watched.

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

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

Forecasting the Evolution of ENSO

Here is the primary NOAA model for forecasting the ENSO Cycle.

CFSv2 spread and bias correct ENSO forecast

This model is forecasting a La Nina. It probably is the most aggressive model re being so definitive about the ENSO Phase for this Fall and Winter.

Click here to see a month by month version of the same model but without some of the correction methodologies applied. It gives us a better picture of the further out months as we are looking at monthly estimates versus three-month averages.

From Tropical

CDAS Legacy System

The above is from a legacy "frozen" NOAA system meaning the software is maintained but not updated. Notice since mid-July the collapse of Nino 3.4 values from the range of 0.5C to 0.6C down to Zero C and then down to -0.9C but recently moved back closer to 0C.

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. Below is the October 12 and October 19 CPC/IRI ENSO Forecasts

CPC/IRI October 19, 2017 ENSO Forecast

And here is the new one.

November 20, 2017 CPC/IRI ENSO 3.4 forecast.

You might notice the pattern here that the early month forecasts that are partly based on a survey have meteorologists has not changed. In between the October and recent forecast there was the second week model based forecast. So my conclusion is that there has been no change.  Also when you look at this graph you see four blue bars in the earlier graph and only three in the mid-month graph but that is because the  early graph  has OND in it and the second graph does not. So it really is not a big change except for FMA which favored La Nina in the early survey based analysis and now favors ENSO Neutral which is not a surprise to us.

And here is the updated discussion.

IRI Technical ENSO Update Published: November 20, 2017

Note: The SST anomalies cited below refer to the OISSTv2 SST data set, and not ERSSTv4. OISSTv2 is often used for real-time analysis and model initialization, while ERSSTv4 is used for retrospective official ENSO diagnosis because it is more homogeneous over time, allowing for more accurate comparisons among ENSO events that are years apart. During ENSO events, OISSTv2 often shows stronger anomalies than ERSSTv4, and during very strong events the two datasets may differ by as much as 0.5 C. Additionally, the ERSSTv4 may tend to be cooler than OISSTv2, because ERSSTv4 is expressed relative to a base period that is updated every 5 years, while the base period of OISSTv2 is updated every 10 years and so, half of the time, is based on a slightly older period and does not account as much for the slow warming trend in the tropical Pacific SST.

Recent and Current Conditions

In mid-November 2017, the NINO3.4 SST anomaly was in the weak La Niña category, and during the most recent weak was near the borderline of moderate La Niña. For October the SST anomaly was -0.46 C, near the borderline of ENSO-neutral and weak La Niña, and for August-October it was -0.35 C, in the cool ENSO-neutral range. The IRI’s definition of El Niño, like NOAA/Climate Prediction Center’s, requires that the SST anomaly in the Nino3.4 region (5S-5N; 170W-120W) exceed 0.5 C. Similarly, for La Niña, the anomaly must be -0.5 C or less. The climatological probabilities for La Niña, neutral, and El Niño conditions vary seasonally, and are shown in a table at the bottom of this page for each 3-month season. The most recent weekly anomaly in the Nino3.4 region was -1.1, qualifying for moderate La Niña for just that week. The pertinent atmospheric variables, including the upper and lower level zonal wind anomalies, have been showing patterns suggestive of La Niña, and he Southern Oscillation Index (SOI) has also been above average. Subsurface temperature anomalies across the eastern equatorial Pacific are somewhat below average. Given the current and recent SST anomalies, the subsurface profile and the La Niña patterns in most key atmospheric variables, an official diagnosis of La Niña is warranted and a La Niña Advisory has been issued.

Expected Conditions

What is the outlook for the ENSO status going forward? The most recent official diagnosis and outlook was issued approximately one week ago in the NOAA/Climate Prediction Center ENSO Diagnostic Discussion, produced jointly by CPC and IRI; it stated that La Niña is favored for late fall and winter, with decidedly lower chances for ENSO-neutral. A La Niña Advisory was issued with that Discussion, following two months with a La Niña watch. The latest set of model ENSO predictions, from mid-November, now available in the IRI/CPC ENSO prediction plume, is discussed below. Those predictions suggest that the SST has the greatest chance for staying in the weak La Niña range for November-January through January-March 2017, with a lower but non-negligible probability for ENSO-neutral during that period.

As of mid-November, about 75% of the dynamical or statistical models predicts La Niña conditions for the initial Nov-Jan 2017-18 season, dropping a bit to 68% for the Jan-Mar 2018 season. During this period, no model predicts El Niño conditions, so that the remaining probability is only for neutral conditions. At lead times of 3 or more months into the future, statistical and dynamical models that incorporate information about the ocean’s observed subsurface thermal structure generally exhibit higher predictive skill than those that do not. For the Feb-Apr 2018 season, among models that do use subsurface temperature information, 38% of models predicts neutral conditions and 62% predicts La Niña conditions. For all models, at longer lead times beginning with Mar-May 2018, predictions for ENSO-neutral conditions dominate, with probabilities of 85% or more for Mar-May to May-Jul. At the end of the forecast range, Jun-Aug and Jul-Sep, the probability for El Niño rises to nearly 30% and La Niña probabilities decrease to near zero, leaving just over 70% for neutral.

Caution is advised in interpreting the distribution of model predictions as the actual probabilities. At longer leads, the skill of the models degrades, and skill uncertainty must be convolved with the uncertainties from initial conditions and differing model physics, leading to more climatological probabilities in the long-lead ENSO Outlook than might be suggested by the suite of models. Furthermore, the expected skill of one model versus another has not been established using uniform validation procedures, which may cause a difference in the true probability distribution from that taken verbatim from the raw model predictions.

An alternative way to assess the probabilities of the three possible ENSO conditions is more quantitatively precise and less vulnerable to sampling errors than the categorical tallying method used above. This alternative method uses the mean of the predictions of all models on the plume, equally weighted, and constructs a standard error function centered on that mean. The standard error is Gaussian in shape, and has its width determined by an estimate of overall expected model skill for the season of the year and the lead time. Higher skill results in a relatively narrower error distribution, while low skill results in an error distribution with width approaching that of the historical observed distribution. This method shows probabilities for La Niña between 70 and 75% for Nov-Jan and Dec-Feb, decreasing thereafter to 45% for Feb-Apr and to 15-20% from Apr-Jun through Jul-Sep. Probabilities for neutral conditions begin at 25% for Nov-Jan, first exceed 50% in Feb-Apr, and peak around 75% in Apr-June, after which it drops to less than 50% for Jul-Sep as El Niño probabilities rise to 38% after having been less than 10% through Apr-Jun.  A plot of the probabilities generated from this most recent IRI/CPC ENSO prediction plume using the multi-model mean and the Gaussian standard error method summarizes the model consensus out to about 10 months into the future. The same cautions mentioned above for the distributional count of model predictions apply to this Gaussian standard error method of inferring probabilities, due to differing model biases and skills. In particular, this approach considers only the mean of the predictions, and not the total range across the models, nor the ensemble range within individual models.

In summary, the probabilities derived from the models on the IRI/CPC plume describe, on average, a preference for weak La Niña conditions from Nov-Jan 2017-18 to Jan-Mar 2018, with neutral regaining highest probability status from Feb-Apr through the end of the forecast period in late summer 2018. Chances for El Niño are very small through Apr-Jun 2018, rising to near-climatological probabilities for May-Jul and slightly higher for Jun-Aug and Jul-Sep 2018. A caution regarding this latest set of model-based ENSO plume predictions, is that factors such as known specific model biases and recent changes that the models may have missed will be taken into account in the next official outlook to be generated and issued early next month by CPC and IRI, which will include some human judgment in combination with the model guidance.

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

And the Discussion:

La Niña ALERT: Tropical Pacific near La Niña thresholds

The tropical Pacific is approaching La Niña thresholds. If the current progression continues, and thresholds are exceeded for a sustained period, 2017–18 will be considered a La Niña event. As a result, the Bureau’s ENSO Outlook has been raised to La Niña ALERT meaning there is approximately a 70% chance—or triple the normal likelihood—of La Niña occurring. Climate models suggest that any event is likely to be weak and short-lived. This means it is expected to be very different to the strong 2010–12 La Niña.

Oceanic indicators of ENSO show a clear progression towards La Niña. Tropical Pacific sea surface temperatures (SSTs) have cooled since late winter, and waters beneath the surface remain cooler than average in the eastern Pacific. However, they are currently just shy of La Niña thresholds. Atmospheric indicators such as the Southern Oscillation Index (SOI) and trade winds have shown signs of shifting into a La Niña-like state. In order for La Niña to become established, atmospheric and oceanic indicators need to be reinforcing each other ("coupled"), which will strengthen and sustain these changes (i.e. a positive feedback).

All international climate models suggest further cooling of the tropical Pacific is likely. All models reach La Niña thresholds in December 2017, and most maintain these values until at least February 2018.

International climate models surveyed by the Bureau indicate that further cooling of equatorial Pacific Ocean sea surface temperatures is expected over the next 1 to 3 months. All of the eight models anticipate that SSTs will reach or surpass La Niña thresholds by the end of 2017.

Seven of the eight models sustain the conditions long enough to be considered an event, where persistence for three months is generally the minimum length required. However, the models also suggest any La Niña may be short lived, with tropical Pacific sea surface temperatures warming again by late summer. Warming back towards neutral levels in late summer is typical of the ENSO cycle at that time of year.

La Niña typically brings above average rainfall to eastern Australia during late spring and summer. However, sea surface temperature patterns in the Indian Ocean and closer to Australia are not typical of La Niña, reducing the likelihood of widespread summer rainfall. La Niña can also increase the chance of prolonged warm spells for southeast Australia.

Here is the new JAMSTEC forecast issued on November 1, 2017

November 1, 2017 JAMSTEC Forecast

The discussion is available in the Seasonal Outlook we published on November 18 which can be accessed here.

Indian Ocean IOD (It updates every two weeks)

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


Discussion Issued November 19

Indian Ocean Dipole outlooks

The Indian Ocean Dipole (IOD) is neutral. The weekly index value to 19 November was −0.20 °C. All six of the climate models surveyed by the Bureau indicate that the IOD will remain neutral into early 2018.

The influence of the IOD on Australian climate is weak during December to April. This is because the monsoon trough shifts south over the tropical Indian Ocean changing wind patterns, which prevents the IOD pattern from being able to form.

However, to the south of the traditional Indian Ocean Dipole regions, cooler than average sea surface temperatures in the eastern Indian Ocean may be limiting the feed of moisture over Australia, and opposing more typical La Niña influences.

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

IOD Measurement Regions

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

D. Putting it all Together.

At this time it would seem a La Nina is likely for this Winter and Spring. But the situation for next Summer is not yet clear. However, we are getting very close to being able to forecast the end of this La Nina event.

Forecasting Beyond Five Years.

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

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

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

E. Relevant Recent Articles and Reports

Weather in the News

Improvements in Predicting La Ninas

Not a surprise really as the Spring Prediction Barrier applies mostly to forecasting an El Nino and the best way to look at the ENSO Cycle is as a battery. The Easterlies tend to skim warm water off the surface of the Tropical Pacific and move into the Indo-Pacific Warm Pool. When conditions lead to the discharge of this warm water which creates an El Nino, it takes a while for the battery (IndoPacific Warm Pool) to be recharged. That is why to some extent the stronger the El Nino the more likely a subsequent and long La Nina.

Weather Research in the News

Nothing to Report

Global Warming in the News

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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 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 Western Pacific Westerlies MJO Active Phase MJO Inactive Phase

  • Weaker
  • Stronger
  • Part of Decay Process
  • Counteracts Easterlies
  • Enhances Easterlies
  • Stronger
  • May Create or Stimulate the Onset of El Nino via Kelvin Waves
  • Weaker
  • Part of Decay Process
  • Strengthens Westerlies
  • Weakens Westerlies
  • More likely
  • Stimulates
  • Less likely and weak
  • Retards development of a new La Nina
  • Stimulates the Jet Stream
  • 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 and 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

November 6-, 2017 Revised Historical ONI Readins.

Note: Without fanfare the base climatology was changed from ERSST.V4 to ERSST.V5

The JAS reading was adjusted to -0.2 which remains an ENSO Neutral Reading and the new ASO reading of -0.4 is also 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.

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

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

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

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

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