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posted on 17 December 2016

New Seasonal Outlook Updates from NOAA and JAMSTEC Disagree

Written by Sig Silber

On December 15, NOAA released their Seasonal Outlook (which actually looks out fifteen months). JAMSTEC, which is a Japanese Research Institute, also has issued their Outlook based on their December 1 forecast for ENSO. We will review what have we learned - and address the question:  Are either of these forecasts credible?

 weather.caption for Updates

In this Update, we compare the JAMSTEC temperature and precipitation forecast maps which are for the World with the NOAA temperature and precipitation forecast maps that cover only CONUS and Alaska. We do this primarily for educational purposes. Remember: these are forecasts not guarantees. But the differences between the NOAA and JAMSTEC forecasts are significant - especially in the further-out months - and are mostly related to the differing perspectives on the strength and duration of this Cool ENSO Event. JAMSTEC in their further-out forecast (which is only out to June - August 2017) is reflecting El Nino conditions.

Some Housekeeping Issues

This report will be posted late Saturday December 17 and will be referred to in the Weekly Report for reference until the Saturday after the next NOAA Update on January 19, 2017. The Regular Weekly Report will be published on December 19. If you are reading this Update Report and wish to transfer to the Current Weather and Climate Report, Click here for the list of Weather Posts. That link takes you to the archive of all weather articles written by Sig Silber so you can if the new Weekly Weather Report has been published go there or back to an earlier report but please keep in mind that the graphics in earlier reports in some cases auto-update and the text may no longer apply to the graphics shown. 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.


NOAA Updated Seasonal Outlook

NOAA issued their updated Seasonal Outlook on the third Thursday of the month i.e. December 15, 2016 as is their normal schedule. Let's take a look. In the NOAA maps, the deviations from climatology/normal are color coded but also labeled "A" for more than normal and "B" for less than normal. The area designated EC means Equal Chances of being more or less than normal. JAMSTEC relies on their color coding.

First we will take a look at the Early Outlook for January 2017. It is called the Early Outlook because it will be updated at the end of December. Only the January Outlook is updated at that time.

Temperature

January 2017 Early Temperature Report  Issued on December 15, 2016

Precipitation

January 2017  Early Preciitation Outlook Issued on December 15, 2016

We have nothing to compare these maps with as NOAA does not in their Update provide a forecast for two months out separate from their three-month forecast. Thus I do not have January maps from the November 17 NOAA Report to compare against. And December is not over so we can not really compare the January forecast against December actual. It is probably best to just try to understand what NOAA is trying to convey about January which can be summarized as for temperature, we have a warmer than climatology Southern Tier and New England with a drier than climatology area focused on Montana but extending to the south into Utah. For precipitation, we have drier than climatology along the Southern Tier and wetter than climatology in the North Central states centered on Montana and the Northern Great Lakes. In most cases the anomalies mirror each other as opposites in the Temperature and Precipitation Maps. The exception is the positive anomaly which for temperature shows up in New England but for precipitation shows up to the west in the Upper Great Lakes area.

Now we consider the three-month Outlook.

Notice that the three-month periods are abbreviated e.g. January/February/March is shown as JFM. You will see such abbreviations often in this report.

Prior Temperature Outlook for JFM 2017

JFM 2017 Temperature Outlook Issued November 17, 2016

New Temperature Outlook for JFM 2017

JfM  2017  Temperature Outlook Issued on December 15, 2016

It is almost identical to the prior forecast. The warm anomaly is rotated just a bit counter-clockwise thus in the West the anomaly is further south and along the East Coast the anomaly is further west.

Prior Precipitation Outlook for JFM 2017

JFM 2017 Precipitation Outlook Issued on November 17, 2016

New Precipitation Outlook for JFM 2017

JFM 2017 Precipitation Outlook issued December 15, 2016

It is almost identical but one can see a slight shift to the south in the pattern.  

Now let us focus on the long-term situation and compare the new set of maps with the maps issued on November 17, 2016.

Prior 14 Month Temperature Outlook: JFM  2017 - DJF 2017/2018

14 month Temperature Maps Issues on November 17, 2016

New 14 Month Temperature Outlook: FMA 2017 - JFM 2018

14 Month Temperature Maps Issued on December 15, 2016

To compare maps from one release to another, one needs to remember that the new release drops one three-month period and adds a later one. So to make the comparisons one has to shift the new maps to the right one position and that makes the map on the right drop down to become the left-most map in the next level. I do not have a computer software tool for doing that for you so you have to do it mentally. When I do the comparison, I print the two sets of maps and put them side by side and number the same three-month maps 1, 2, 3,.....,11 in both sets of maps to make it easier for me to easily compare the same three-month period in the new with the previous forecast. One uses the same procedure to compare the precipitation maps. Based on this procedure, I conclude that:

There is essentially no change from the prior forecast. Jan-Feb-Mar 2018 was outside the forecast window last month and shows an EC Northeast Quadrant of CONUS which is a big change from the pattern of warmer than climatology everywhere.

Prior 14 Month Precipitation Outlook: JFM 2017 - DJF 2017/2018

14 Month Precipitation Outlook Issued on November 17, 2016

New 14 Month Precipitation Outlook: FMA 2017 - JFM 2018

14 month precipitation maps Issued on December 15, 2016

Unlike temperature, there are significant changes in the precipitation maps as follows: Mar-Apr-May 2017 (Southeast dry anomaly added, Northern Tier wet anomaly shifted to the east);  Apr-May-Jun 2017 (Mid-West Coast dry anomaly added); May-Jun-Jul 2017 (West Coast dry anomaly shifted to the north). Jan-Feb-Mar 2018 was outside of the forecast window last month but unlike the previous month triplets, the Northern California dry anomaly does not appear in the Jan-Feb-Mar 2018 forecast.

If you want larger versions of each map (temperature and precipitation) you can find them here. And then each of those maps can be clicked on to further enlarge them.

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

January 2017 plus JFM 2017  Issued on December 15, 2016

One can mentally subtract the January Outlook from the three-month Outlook and create the Outlook for the last two months in the three-month period namely February and March 2017. When I do that, I deduce that:

With respect to temperature, The three-month forecast has an elongated cool area across the Northern Tier which in the January map has a smaller east to west coverage but extends further south. This suggests that February and March may have to have the opposite anomaly where the two patterns differ for the three-month average to work out. For precipitation, the same logic applies to the Great Lakes wet anomaly and the Northwest wet anomaly where the Three-Month extent is larger suggesting that areas shown as wet in the three-month map but not in January will need to have even higher probabilities of being wet in February and March for the three-month average to work out.
The whole idea is that a three-month average set of probabilities for anomalies is the sum of that information for three months. If you have the first month differing in places from the three-month average you can calculate what a map of the second and third month would look like for the sum of the two maps (January and February/March) to equal the published three-month map.

Below are excerpts (significantly reorganized and with a lot of the redundancy removed) from the Discussion released by NOAA on December 15, 2016. Headings that are "Initial Cap" only rather than all caps were added by the Author of this Update Report for clarity. Also we have organized the sequence of the sections of NOAA Discussion to first present the Atmospheric Conditions and then the Current Month, the Three or Four-month period, and finally the remainder of the 15 Month Forecast. We think that sequence with the three- to four-month period broken out separately, makes the discussion more useful for more readers.

Discussion

Below are excerpts (significantly reorganized and with a lot of the redundancy removed) from the Discussion released by NOAA on December 15, 2016. Headings that are "Initial Cap" only rather than all caps were added by the Author of this Update Report for clarity. Also we have organized the sequence of the sections of NOAA Discussion to first present the Atmospheric Conditions and then the Current Month, the Three or Four-month period, and finally the remainder of the 15 Month Forecast. We think that sequence with the three- to four-month period broken out separately, makes the discussion more useful for more readers.

CURRENT ATMOSPHERIC AND OCEANIC CONDITIONS  

OCEANIC AND ATMOSPHERIC OBSERVATIONS INDICATE THAT LA NINA CONDITIONS ARE CURRENTLY PRESENT. [Editor's Note: We totally disagree with that statement and discuss it more later]. DURING THE PAST FOUR WEEKS, EQUATORIAL SSTS REMAINED BELOW (ABOVE)-AVERAGE ACROSS THE CENTRAL AND EASTERN PACIFIC OCEAN (NEAR THE MARITIME CONTINENT). NEGATIVE ANOMALIES CONTINUE TO BE RELATIVELY SMALL FROM THE DATE LINE TO THE SOUTH AMERICAN COAST. NEGATIVE SUBSURFACE TEMPERATURE ANOMALIES HAVE PERSISTED SINCE APRIL ACROSS THE CENTRAL AND EASTERN PACIFIC. HOWEVER, THESE ANOMALIES WEAKENED DURING NOVEMBER. THE MOST RECENT ONI VALUE (SEPTEMBER - NOVEMBER 2016), BASED ON SST DEPARTURES FROM AVERAGE IN THE NINO 3.4 REGION, IS -0.8 DEGREES C.

ENHANCED CONVECTION REMAINS CENTERED OVER THE MARITIME CONTINENT, WITH SUPPRESSED CONVECTION EXTENDING EASTWARD FROM 160E ACROSS MUCH OF THE EQUATORIAL PACIFIC. DURING THE PAST COUPLE OF MONTHS, SUBSEASONAL VARIABILITY HAS DISRUPTED THIS PATTERN AND LED TO PERIODIC DRYING ACROSS PARTS OF THE MARITIME CONTINENT AND EASTERN INDIAN OCEAN. TRADE WINDS AVERAGED NEAR NORMAL ACROSS THE CENTRAL AND EASTERN EQUATORIAL PACIFIC FROM NOVEMBER 10 TO DECEMBER 9, 2016.

THE ATMOSPHERIC CIRCULATION DURING OCTOBER FORCED A DRAMATIC COOLING OVER THE NORTH-CENTRAL PACIFIC BASIN. AS OF EARLY DECEMBER, NEGATIVE ANOMALIES ARE NOW PRESENT OVER THE NORTH PACIFIC, CENTERED AT 40N-150W. [Editor's Note: This is very important and has impacted CONUS weather in recent months and will continue to as long as that pattern persists]. POSITIVE SST ANOMALIES, ALBEIT WITH SMALLER MAGNITUDE, CONTINUE FROM THE COASTAL PACIFIC NORTHWEST NORTH TO THE ALASKA PANHANDLE.

PROGNOSTIC DISCUSSION OF SST FORECASTS

THE CPC SST CONSOLIDATION FORECAST, WHICH INCLUDES THREE STATISTICAL FORECASTS ALONG WITH THE CFS, PREDICTS A TRANSITION FROM LA NINA TO ENSO-NEUTRAL CONDITIONS DURING JFM AND FMA 2017 WITH ENSO-NEUTRAL CONDITIONS FAVORED THEREAFTER. THE NORTH AMERICAN MULTI MODEL ENSEMBLE (NMME) ENSEMBLE MEAN FORECAST FOR THE NINO-3.4 SST ANOMALY IS SLIGHTLY WARMER THAN LAST MONTH, WITH ENSO-NEUTRAL FAVORED EARLY IN OUTLOOK PERIOD. BASED ON THE LATEST OBSERVATIONAL AND MODEL FORECAST INDICATORS, THE OFFICIAL CPC/IRI ENSO OUTLOOK FAVORS ENSO-NEUTRAL CONDITIONS AT 55% DURING JFM 2017.

WEAK LA NINA CONDITIONS CONTINUE ACROSS THE EQUATORIAL PACIFIC OCEAN, AS REPRESENTED IN CURRENT OCEANIC AND ATMOSPHERIC OBSERVATIONS. THE OFFICIAL CPC ENSO FORECAST INDICATES A TRANSITION TO ENSO-NEUTRAL CONDITIONS DURING JANUARY-MARCH 2017. [Editor's Note: That is only the case because both NOAA and CPC/IRI publish on December 15 and NOAA apparently has not incorporated the latest information from CPC/IRI which calls for a faster transition and we believe that transition has already occurred] the end of  ENSO-NEUTRAL CONDITIONS ARE FAVORED TO PERSIST THROUGH AT LEAST THE BOREAL SUMMER.

30-DAY OUTLOOK DISCUSSION FOR JANUARY 2017

THE JANUARY 2017 TEMPERATURE AND PRECIPITATION OUTLOOKS ARE BASED ON DYNAMICAL MODEL OUTPUTS, STATISTICAL TOOLS, TYPICAL PATTERNS ASSOCIATED WITH TROPICAL SST VARIABILITY, AND THE LIKELY STATES OF PATTERNS OF EXTRATROPICAL VARIABILITY. LA NINA CONDITIONS CONTINUE OVER THE TROPICAL PACIFIC, AND ARE EXPECTED TO CONTINUE THROUGH JANUARY 2017, THOUGH IMPACTS ON THE MONTHLY TIMESCALE FROM ENSO ARE LESS ROBUST THAN SEASONAL IMPACTS. CLIMATE SIGNALS ASSOCIATED WITH LA NINA ARE CONSIDERED AS A PORTION OF THE OUTLOOK.

THE MJO IS NOT CURRENTLY ACTIVE, AND THE UNCERTAINTY FOR INTRASEASONAL VARIABILITY IS HIGH, SO THE MJO DID NOT PLAY A ROLE IN THE OUTLOOK. ITS EVOLUTION WILL BE CLOSELY MONITORED FOR THE REVISED OUTLOOK AT THE END OF DECEMBER.

THE DYNAMICAL MODEL OUTLOOKS FOR JANUARY 2017 EXHIBITED GOOD AGREEMENT, WHEREAS LAST MONTH THE OUTLOOKS FOR DECEMBER HAD BETTER AGREEMENT, SO THE CONFIDENCE IN THE OUTLOOK IS SLIGHTLY LOWER, RESULTING IN LOW TO MODERATE COVERAGE. LA NINA CONDITIONS WOULD FAVOR ABOVE NORMAL TEMPERATURES OVER THE SOUTHERN CONUS WITH BELOW NORMAL TEMPERATURES OVER MUCH OF THE NORTHERN CONUS. THE SPATIAL COVERAGE OF WHERE BELOW NORMAL TEMPERATURES ARE FAVORED OVER THE NORTHERN ROCKIES AND NORTHERN GREAT PLAINS IS SMALLER THAN A TYPICAL SEASONAL FOOTPRINT OF LA NINA, DUE TO LOWER PREDICTABILITY AND DYNAMICAL MODEL GUIDANCE. SOME STATISTICAL TOOLS FAVOR BELOW NORMAL TEMPERATURES EXTENDING INTO NORTHERN COLORADO. SOME DYNAMICAL MODELS INDICATE A SLIGHT TILT TOWARD A NEGATIVE ARCTIC OSCILLATION THROUGHOUT THE WINTER, WHICH FAVORS PERIODS OF COLDER AIR MOVING SOUTHWARD OVER THE GREAT PLAINS, SO PROBABILITIES FOR ABOVE NORMAL TEMPERATURES ARE LOWER THAN INDICATED IN MODEL GUIDANCE OVER THE GREAT PLAINS AND MID-ATLANTIC. ABOVE NORMAL SSTS FAVOR ABOVE NORMAL TEMPERATURES FOR WESTERN ALASKA AND THE ALEUTIANS.

THE PRECIPITATION OUTLOOK FOR JANUARY 2017 REFLECTS CALIBRATED NMME OUTPUT AND IS CONSISTENT WITH TRADITIONAL LA NINA IMPACTS DURING DJF AND JFM. COVERAGE AND PROBABILITIES FOR THE CATEGORIES ARE LOWER THAN IF LA NINA WAS THE ONLY FACTOR, AS SIGNALS IN THE DYNAMICAL MODELS ARE WEAKER, AND LA NINA IMPACTS ON A SINGLE MONTH OF A SEASON ARE LESS PRONOUNCED THAN IMPACTS ON AN ENTIRE SEASON. BELOW MEDIAN PRECIPITATION IS FAVORED FOR THE SOUTHERN CONUS, WITH ABOVE MEDIAN PRECIPITATION FAVORED ALONG THE ROCKIES AND OVER THE GREAT LAKES REGION, WITH A MORE ACTIVE NORTHERN STORM TRACK. ABOVE NORMAL SSTS, BELOW NORMAL SEA ICE COVERAGE IN THE BERING SEA, AND MODEL GUIDANCE FAVOR ABOVE MEDIAN PRECIPITATION

Three Month Forecast JFM

Temperature

THE JANUARY-FEBRUARY-MARCH (JFM) 2017 TEMPERATURE OUTLOOK FAVORS ABOVE-NORMAL TEMPERATURES ALONG THE EAST COAST AND ACROSS THE SOUTHERN TIER OF THE CONUS, WITH THE HIGHEST ODDS (GREATER THAN 50 PERCENT) FORECAST ACROSS PARTS OF NEW MEXICO AND TEXAS. ABOVE-NORMAL TEMPERATURES ARE ALSO FAVORED FOR WESTERN AND NORTHERN ALASKA. INCREASED CHANCES FOR BELOW-NORMAL TEMPERATURES DURING JFM ARE FORECAST FROM PARTS OF THE PACIFIC NORTHWEST EAST TO THE NORTHERN GREAT PLAINS AND UPPER MISSISSIPPI VALLEY.

THE LARGEST CHANGE IN THE CALIBRATED PROBABILISTIC NMME FORECAST FROM ONE MONTH AGO IS A COLDER SOLUTION FOR THE NORTHWESTERN U.S. FOR JFM 2017 [Editor's Note: this does not appear to be a change from the map released on November 17, 2016]. THEREFORE, BELOW-NORMAL TEMPERATURES ARE FAVORED FOR PARTS OF THE PACIFIC NORTHWEST AND NORTHERN ROCKIES ALBEIT WITH MODEST PROBABILITIES. THE TEMPERATURE OUTLOOK REMAINS UNCERTAIN ACROSS THE NORTHERN AND CENTRAL GREAT PLAINS, GREAT LAKES, AND MIDWEST. STATISTICAL METHODS OFFER A COLDER SOLUTION ACROSS THESE AREAS COMPARED TO THE VARIOUS DYNAMICAL MODELS. BELOW-NORMAL TEMPERATURES ARE SLIGHTLY FAVORED ACROSS THE NORTHERN GREAT PLAINS AND UPPER MISSISSIPPI VALLEY, BUT THE TEMPERED PROBABILITIES REFLECT THE CONTINUED UNCERTAINTY IN THE TEMPERATURE OUTLOOK FOR THIS REGION. INCREASED CHANCES OF ABOVE-NORMAL TEMPERATURES, FORECAST ACROSS THE SOUTHERN TIER OF THE CONUS, ARE BASED LARGELY ON A CONSENSUS AMONG THE TOOLS. THE HIGHEST ODDS FOR ABOVE-NORMAL TEMPERATURES (GREATER THAN 50 PERCENT) ARE FORECAST ACROSS THE SOUTHWEST DUE TO TRENDS AND GOOD AGREEMENT BETWEEN DYNAMICAL MODELS AND STATISTICAL TOOLS.

SUBSEASONAL TROPICAL VARIABILITY SUCH AS THE MADDEN-JULIAN OSCILLATION, ESPECIALLY DURING JANUARY AND FEBRUARY WHEN VARIANCE IS HIGHEST, MAY PLAY A ROLE IN DETERMINING THE OBSERVED TEMPERATURE FIELD DURING JFM 2017 ACROSS THE CENTRAL AND EASTERN U.S. IF ENHANCED CONVECTION REMAINS CENTERED OVER THE MARITIME CONTINENT AND FAR WESTERN PACIFIC, THE COLDER OUTCOME INDICATED BY STATISTICAL GUIDANCE IS MORE LIKELY ACROSS THE NORTHERN CONUS. FOLLOWING A TWO MONTH PERIOD OF A NEGATIVE ARCTIC OSCILLATION (AO), THIS INDEX HAS RECENTLY BECOME POSITIVE DURING EARLY DECEMBER. THE GFS MODEL INDICATES THAT A POSITIVE AO INDEX WILL PERSIST INTO THE LATTER HALF OF DECEMBER. DUE TO POOR MODEL PERFORMANCE SINCE EARLY NOVEMBER WITH THE AO INDEX FORECAST, ITS STATUS IS UNCERTAIN ENTERING JANUARY 2017 AND ITS POTENTIAL INFLUENCE IS UNKNOWN AT THIS TIME.

Precipitation

THE JFM 2017 PRECIPITATION OUTLOOK INDICATES ENHANCED PROBABILITIES OF ABOVE-MEDIAN PRECIPITATION AMOUNTS FOR THE PACIFIC NORTHWEST ALONG WITH NORTHERN AREAS OF THE GREAT BASIN, ROCKIES, AND HIGH PLAINS. INCREASED CHANCES OF ABOVE MEDIAN-PRECIPITATION ARE ALSO FAVORED FROM THE GREAT LAKES SOUTH TO THE OHIO AND TENNESSEE VALLEYS ALONG WITH PARTS OF ALASKA. BELOW-MEDIAN PRECIPITATION AMOUNTS ARE MOST LIKELY FOR SOUTHERN CALIFORNIA, THE SOUTHWEST, SOUTHERN GREAT PLAINS, GULF COAST, FLORIDA, AND THE SOUTHERN ATLANTIC COASTAL AREAS.

THE JFM 2017 PRECIPITATION OUTLOOK IS BASED ON THE CALIBRATED DYNAMICAL MODEL GUIDANCE FROM THE NMME AND IS CONSISTENT WITH LINGERING EFFECTS FROM THE CURRENT LA NINA EVENT.

PROGNOSTIC DISCUSSION OF OUTLOOKS - JFM 2017 TO JFM 2018 (Focus on the months beyond JFM 2017)

TEMPERATURE

THE TEMPERATURE OUTLOOK FOR FMA 2017 IS VERY SIMILAR TO JFM WITH LITTLE CHANGES APPARENT AMONG THE DYNAMICAL AND STATISTICAL TOOLS. AS A SHIFT TO ENSO-NEUTRAL CONDITIONS IS LIKELY TO OCCUR DURING THE NEXT THREE MONTHS, THE TEMPERATURE OUTLOOKS FROM MAM THROUGH MJJ 2017 ARE BASED LARGELY ON THE CALIBRATED PROBABILISTIC FORECASTS FROM THE NMME ALONG WITH TRENDS. BEYOND MJJ 2017, NO CHANGES WERE MADE TO THE TEMPERATURE OUTLOOKS FROM THE PREVIOUS OUTLOOKS. DURING THE WINTER 2017-18, THE TEMPERATURE OUTLOOKS ARE BASED ON TRENDS.

PRECIPITATION

MODEST PROBABILITIES, SIMILAR TO THE TEMPERATURE OUTLOOK AT THIS EARLY LEAD, REFLECT CONTINUED UNCERTAINTY ON THE HOW MUCH INFLUENCE THE WEAKENING LA NINA HAS ON THE CLIMATE PATTERN ACROSS THE MIDDLE LATITUDES. COVERAGE OF FAVORED AREAS FOR ANOMALOUS PRECIPITATION DECREASE FROM FMA THROUGH AMJ 2017 AS FORECAST CONFIDENCE DIMINISHES WITH A WEAKENING SIGNAL AMONG PRECIPITATION TOOLS.

DURING JJA AND JAS 2017, BELOW (ABOVE)-MEDIAN PRECIPITATION FAVORED FOR THE PACIFIC NORTHWEST (NEW ENGLAND) IS RELATED TO HISTORICAL TRENDS. BY NEXT WINTER 2017-18, INCREASED CHANCES OF BELOW-MEDIAN PRECIPITATION FORECAST ACROSS PARTS OF THE SOUTHEAST AND ALONG THE WEST COAST ARE ALSO BASED ON TRENDS.

NOAA indicates that they are not clear as to the forecast for the Arctic Oscillation (AO). It can be very important during the Winter Months so I will repeat part of the discussion from last month.

Arctic Oscillation (AO) Courtesy of the State Climate Office of North Carolina

The Arctic Oscillation (AO) is a climate index of the state of the atmospheric circulation over the Arctic. It consists of a positive phase, featuring below average geopotential heights, which are also referred to as negative geopotential height anomalies, and a negative phase in which the opposite is true. In the negative phase, the polar low pressure system (also known as the polar vortex) over the Arctic is weaker, which results in weaker upper level winds (the westerlies). The result of the weaker westerlies is that cold, Arctic air is able to push farther south into the U.S., while the storm track also remains farther south. The opposite is true when the AO is positive: the polar circulation is stronger which forces cold air and storms to remain farther north. The Arctic Oscillation often shares phase with the North Atlantic Oscillation (NAO) and its phases directly correlate with the phases of the NAO concerning implications on weather across the U.S. and Europe.

Perhaps the following graphics side by side for comparison may be helpful. The warm phase (AO+) is on the left, the cool phase (AO-) on the right. You can click on them to get a larger version.

AO Positive

Cool Phase

 

There are two parts to this discussion: the atmospheric factors that cause the two phases and the impacts on weather which is mainly the location and strength of the jet stream and both are shown in these graphics.

Forecasting the Evolution of ENSO

Here is the latest NOAA forecast of Nino 3.4 temperature anomalies. This graphic does auto-update daily but changes slowly. You can see the "blue" newer model runs and the "red" older model runs. The Oceanic Niño Index (ONI) which is the three-month rolling average of the Nino 3.4 values is NOAA's primary indicator for monitoring El Niño and La Niña. The secondary indicator is the Southern Oscillation Index (SOI) which is based on the extent that the air pressure anomaly in Tahiti exceeds the air pressure anomaly in Darwin Australia.  It is a complicated formula and is intended to assess the response of the atmosphere to the changes in the pattern of warm and cool anomalies measured by the Nino 3.4 Index. It confirms rather than predicts the phases of ENSO.

 CFS.V2 SST Forecast
At this point in time, the forecast by the NOAA model is that Nino 3.4 no longer is sufficiently cool (-0.5C or cooler) to be considered a La Nina (but NOAA does not say this) and is expected to continue to be less cool. NOAA clams the atmosphere has recently confirmed that borderline La Nina Conditions apply but the SOI does not support that conclusion as shown below. The ultimate recording of this as a La Nina event depends on the duration requirements being met and that may or may not occur and at this point it seems that will not occur. It will be close but we wonder why NOAA insists on promoting the idea that we are having a La Nina when it is clear that this Cool Event does not fully meet the criteria to be recorded as a La Nina. In reality, fully meeting the criteria or just barely missing may have little impact on the weather that occurs.

Re The SOI

SOI values as of December 15, 2016

Normally La Nina Conditions are confirmed by SOI 30 day values that are greater than or equal to +7.0. As you can see, that was the case in September but not October or the last 30 days. So any claims that the atmosphere is showing La Nina is questionable at the very least.

And now we have the IRI/CPC December 15, 2016 fully model-based report.

December 15, 2016 Model Based ENSO Forecast

Here is the discussion that was released with the graphic.

What is the outlook for the ENSO status going forward? The most recent official diagnosis and outlook was issued one week ago in the NOAA/Climate Prediction Center ENSO Diagnostic Discussion, produced jointly by CPC and IRI; it carries a La Niña advisory and called for weak La Niña to last through winter 2016-17 (i.e., for December-February), and for a transition to neutral to occur by late winter. The latest set of model ENSO predictions, from mid-December, now available in the IRI/CPC ENSO prediction plume, is discussed below.  Those predictions suggest that the SST could remain in the weak La Niña category during the rest of 2016 and into the early part of 2017, or may return to neutral by the New Year. [Editor's Note: The Nino 3.4 has already warmed above La Nina criteria and the SOI has been neutral for over two months]

As of mid-November [Editor's Note: Not sure if they meant to say November or December], 17% of the dynamical or statistical models predicts La Niña conditions for the initial Dec-Feb 2016-17 season, while 83% predict neutral ENSO.  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 Mar-May 2017 season, among models that do use subsurface temperature information, no model predicts La Niña conditions, 89% predicts ENSO-neutral conditions, and 11% predicts El Niño conditions. For all model types, the probabilities for La Niña are 9% for Jan-Mar 2016-17, and less than 5% for all subsequent seasons out to Aug-Oct 2017. The probability for neutral conditions is at least 70% for all seasons through the final season of Aug-Oct 2017, and rise to greater than 90% from Jan-Mar through Apr-Jun 2017. Probabilities for El Niño are near zero initially, rise to 5-10% by Mar-May 2017, and to 25-30% from Jun-Aug through the final season of Aug-Oct.

Heading into the first quarter of 2017, the model-based results indicate that ENSO Neutral is 70% likely.

Here is the recently released JAMSTEC Nino 3.4 Forecast.

JAMSTEC December 1, 2016 ENSO Forecast.

Based on the Nino 3.4 projection, JAMSTEC is saying "no" to (other than a borderline) La Nina for this winter but is raising the possibility of an El Nino for the following winter.

Here is the Nino 3.4 report from the Australian BOM. It will update automatically on Tuesday morning or late Monday night.

Australia POAMA ENSO model run

This is basically the same forecast as other agencies but with different threshold for considering a SST to be either La Nina or El Nino and slightly higher values than NOAA through November so BOM does not show anything other than ENSO Neutral.

Now the Comparison of the NOAA and JAMSTEC Forecasts. I am only discussing the differences for CONUS since NOAA does not cover the World in this set of forecasts. But the JAMSTEC World forecast is here for you to see and I comment on the highlights of that forecast also.

JAMSTEC works in three-month intervals and does not change the selection of months each time they update. So we have DJF, MAM, and JJA to work with from JAMSTEC. This creates a problem as I have a DJF from JAMSTEC but not a JFM so I either have to compare the new DJF from JAMSTEC with the new JFM from NOAA or the old DJF from NOAA and I decided to do that to minimize confusion. It is not the ideal situation but the choice I made from two bad choices. Fortunately the new JFM from NOAA is not very different than the old DJF from NOAA. And earlier in this report the new JFM from NOAA are shown and if anyone wants to do so they can compare the new NOAA JFM maps with the JAMSTEC DJF maps.
I show the JAMSTEC forecast map first and comment on it and then I show the NOAA map and comment on it and compare it to the JAMSTEC map that is above the NOAA map. I hope this approach is not too confusing.

DJF 2016/2017

Temperature

JAMSTEC

DJF 2016.2017 Temperature JAMSTEC

It is mostly warm but with notable cool areas in Northern Brazil, Australia, and North America.

NOAA

DJF 2016 NOAA Temperature Issued on November 17, 2016

NOAA shows a cool anomaly across North Central CONUS and below that a lot of EC with Alaska having a warm coast and EC interior. JAMSTEC in their graphic above forecasts for CONUS more of a Northeast cool/Southwest warm divide rather than simply north/south. Overall JAMSTEC is a cooler forecast for CONUS.  .

Precipitation

JAMSTEC

D 2016 JF Jamstec Precipitation Forecast

Of interest is the wet Brazil and dry Maritime Continent and Japan. There is really somewhat of a Northern Hemisphere/Southern Hemisphere divide.

And then to get more focus, I extracted and enlarged an image for CONUS on the left and Europe on the right.

 

For many purposes 55N latitude is the dividing line in Europe in regards to the Arctic Oscillation (AO) and the North Atlantic Oscillation (NAO) Impacts. You see that here with Scandinavia wet and southern Europe dry. It is suggestive of AO+. The NAO is highly correlated with the AO so it is also suggestive of NAO +. For CONUS it is a La Nina Neutral pattern and different than shown below for NOAA and it is not a North/South divide but a West/East divide. NOAA has not offered a forecast for the AO or NAO and I do not yet have the discussion from JAMSTEC but it appears that JAMSTEC is forecasting a mostly positive AO and NAO. 

NOAA

NOAA DJF 2016 - 2017 Precipitation Issued November 17, 2016

Notice the different pattern between NOAA and JAMSTEC as per their graphic above. NOAA is classical La Nina. JAMSTEC is not. NOAA may have it correct but they also may not. I suspect that they do not.

MAM 2017

Temperature

JAMSTEC

MAM 2017 JAMSTEC Temp

A lot more cooler areas: Europe: Siberia and Mongolia, Australia, Part of Brazil, North Central CONUS and West Africa

NOAA

MAM Temperature NOAA Issued on December 15, 2016

NOAA has a large part of the Northern Tier being EC with JAMSTEC in their graphic above showing it cool. There is a lot of similarity here.

Precipitation

JAMSTEC

MAM 2017 JAMSTEC Precipitation Forecast

Again there seems to be a Northern Hemisphere/Southern Hemisphere Divide. Southern Africa is very wet. Eastern Australia is wet. Most of South America below Venezuela and Columbia is wet and most of CONUS is wet. Scandinavia is dry.

NOAA

NOAA MAM 2017 Precipitation Issued on December 15, 2016October 20, 2016

NOAA still has a north/south La Nina divide but impacting only parts of the Southern Tier (dry) and an extended Great Lakes Area wet. There is quite a bit of agreement with JAMSTEC as described in their graphic above but JAMSTEC is a bit wetter.

JJA 2017 (And this is a period of time where JAMSTEC is essentially predicting an El Nino or Near El Nino)

Temperature

JAMSTEC

JJA 2017 JAMSTEC Temperature

JAMSTEC has Europe cool, Northern Australia cool, CONUS and Southern Canada cool and parts of Eastern Siberia cool and Libya and Egypt cool. Most of the rest is warm with very little EC (white coloration).  

NOAA

NOAA JJA 2016 Temperature Issued on December 15, 2016

Strange! JAMSTEC in their graphic above finally goes all in with a mostly cool CONUS except warm for the Southeast.  NOAA is all warm including Alaska with a small EC area for the Dakotas.

Precipitation

JAMSTEC

JJA 2017 JAMSTEC Precipitation Forecast

Europe is wet, North America is wet except for CONUS Southeast, and Australia is dry.

NOAA

JJA 2017 Precipitation Issued December 15, 2016

NOAA is mostly EC with a wet New England and dry Northwest.  NOAA is forecasting a normal Southwest Monsoon.  JAMSTEC as shown in their graphic above is forecasting a fairly wet Monsoon but a dry Southeast..

Conclusion

Most of the differences can be explained by the differing forecasts for ENSO with NOAA being far more all in on the La Nina scenario than JAMSTEC. It  results in very different forecasts, especially beyond three months as JAMSTEC trends towards a forecast with El Nino characteristics.

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

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