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posted on 21 October 2017

October, 2017 Seasonal Outlook Update - NOAA and JAMSTEC

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NOAA and JAMSTEC  have substantially similar but not identical ideas on the ENSO forecast which is the key to the Seasonal Outlook. Both see a "cool" Eastern Equatorial Ocean pattern with NOAA being more optimistic than JAMSTEC that it will be a true La Nina. This results in closer agreement than usual for the temperature and precipitation forecasts for at least the first two Seasons. The details on this are discussed in this report.

Seasonal Outlook Update


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This report is organized into two Parts:

A. A full discussion of the recent NOAA Seasonal Outlook

B. A comparison between the NOAA and JAMSTEC Forecasts.

But for those who want a quick synopsis of the two forecasts, below is a summary of the temperature and precipitation forecasts for three time-periods and from left to right the NOAA forecast for Alaska and CONUS (the contiguous mid-latitude U.S), then JAMSTEC for North America (which includes Canada and Northern Mexico), and then JAMSTEC for Europe and surrounding areas. Larger graphics are provided later in the report. It is kind of a tease to keep you reading but you can see the evolution of the weather pattern through Winter, Spring and into Summer. For some readers, these two sets of summary graphics may be all the information they wish to look at and that is fine.

Temperature

  NOAA Alaska Plus CONUS JAMSTEC North America JAMSTEC Europe

DJF

Winter

2017-2018

Temp

DJF 2017-2018  US Temperature Issued on October 19, 2017, NOAA Forecast DJF 2017 -2018 NA Temperature Based on Oct 1, 2017 JAMSTEC Forecast DJF 2017 - 2018 Europe Temperature JAMSTEC Oct 1, 2017 Forecast

MAM

Spring

2018

Temp

MAM 2018 US Temperature Issued by NOAA on October 19, 2017 MAM 2018  NA Temperature based on JAMSTEC Oct 1, 2017 Forecast MAM  - 2018 Europe Temperature based on JAMSTEC Oct 1 2017 Forecast

JJA 2018

Summer

Temp

JJA 2018 Temperature Issued by NOAA on October 19, 2017 JJA 2018 NA Temperature based on Oct 1 JAMSTEC Forecast JJA 2018 Europe Temperature Based on Oct 1, 2017 Jamstec Forecast

There are not a lot of changes by season in the NOAA forecasts for CONUS and Alaska but there is quite a bit by JAMSTEC with MAM 2018 showing a lot of cool area  along the Northern Tier. For Europe, the cool winter for North Africa shows up in the Europe graphic.

Precipitation

  NOAA Alaska Plus CONUS JAMSTEC North America JAMSTEC Europe

DJF

Winter

2017/2018

Precip

DJF 207 - 2008 US Precipitation Issued by NOAA on October 19, 2017 DJF 2017-2018  NA Precipitation Based on Oct 1, 2017 JAMSTEC Forecast DJF 2017-2018 Europe JAMSTEC Precipitation Oct 1, 2017 Forecast

MAM

Spring

2018

Precip

NOAA MAM Precipitation Issued on October 19, 2017 MAM 2018 NA Precipitation based on JAMSTEC Oct 1, 2017 Forecast MAM- 2018 Europe Precipitation based on JAMSTEC Oct 1, 2017 Forecast

JJA

Summer

2018

Precip

JJA 2018 Precipitation issued by NOAA on October 19, 2017 JJA 2018 US Precipitation based on Oct 1, JAMSTEC Forecast JJA 2018 Europe Precipitation Based on Oct , 2017 Jamstec Forecast

For NOAA, there is a big change from Winter to Spring. JAMSTEC has the CONUS Southeast dry for the Summer. JAMSTEC tends to keep Europe dry for all three seasons.
NOAA DJF 2017/2018 SST
djf 2017/2018 JAMSSTEC SST based on Oct 1, 2017 nino 3.4

I do not usually present these graphics (there are an endless number of graphics that could be presented), but this graphic often very clearly shows the difference in the forecasts between NOAA and JAMSTEC because weather is determined by patterns of sea surface temperature (SST) variances from normal. These two graphics show the two forecasts for SST's for DJF 2017/2018
They are not identical but quite close to each other. So we would expect that the two Agencies would be viewing DJF 2017/2018 in a very similar way and in general they are. But there are differences.

A. Focus on the NOAA Update

A note about terminology; 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. In my comments I have used EC to cover all the situations where a clear anomaly is not shown.

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

Temperature

November 2017 Early Temperature Report Issued on October 19, 2017

Precipitation

November 2017 Early Precipitation Outlook Issued on October 19, 2017

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 November maps from the September 21, NOAA Report to compare against. And October is not over so we can not really compare the November forecast against October actual. It is probably best to just try to understand what NOAA is trying to convey about November which can be summarized as for temperature, the Southwest, New England and Northern Alaska will be warm with the rest EC.  Re precipitation, the Southern Tier except Arizona will be dry, Montana and parts of neighboring states will be wet and northern Alaska will be wet.

Now we consider the three-month Outlook.

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

Prior Temperature Outlook for NDJ 2017-2018

NDJ 2017/2018 Temperature Outlook Issued September 21,  2017

New Temperature Outlook for NDJ 2017-2018

NDJ 2017 - 2018  Temperature Outlook Issued on October 19, 2017

The temperature forecast is not much changed with some areas having higher probabilities of being warmer than in the forecast for this three months that was issued last month.

Prior Precipitation Outlook for NDJ 2017 - 2018

NDJ 2017/2018 Precipitation Outlook Issued on September 21, 2017

New Precipitation Outlook for NDJ 2017 - 2918

NDJ 2017 - 2018 Precipitation Outlook issued October 19, 2017

The new precipitation forecast has the wet anomaly in the north further east and away from the coast. The dry anomaly in the southern tier extends somewhat farther north ans west than in the prior forecast.

Now let us focus on the long-term situation and compare the new set of maps with the maps issued on July 20, 2017.

Prior 14 Month Temperature Outlook: NDJ 2017 - OND 2018

14 Month Temperature Issued on September 21, 2017

New 14 Month Temperature Outlook: DJF 2017/2018 - NDJ 2018/2019

14 month Temperature Issued on October 19, 2017

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:

The addition of the CONUS Northern Tier cool anomaly continues through MAM 2018 and for Southern Alaska and the Panhandle it continues through FMA 2018.

Now Precipitation

Prior 14 Month Precipitation Outlook: NDJ 2017 - OND 2018

14 Month Preipitation Forecast Issued September 21, 2017

New 14 Month Precipitation Outlook: DJF 2017/2018 - NDJ 2018/2019

14 Month Precipitation Issued on October 19, 2017

For precipitation, the changes are the connection of the two Northern Tier wet anomalies through JFM 2018;  the elimination of the Southwest dry anomaly in MJJ and JJA 2018 and the connection in FMA 2018 of the two previously not connected Southern Tier dry anomalies but with only low probability.

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 

November Plus NDJ 2017 - 2018 Issued on October 19, 2017

One can mentally subtract the First-Month Outlook from the Three-month Outlook and create the Outlook for the last two months in the three-month period.

For both temperature and precipitation if you assume the colors in the maps are assigned correctly, it is a simple algebra equation to solve the month two/three forecast probability for a given location = (3XThree-Month Probability - Month One Probability)/2*. So you can derive the month two/three forecast this way. You can do that calculation easily for where you live or for the entire map.

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

Discussion

Below are excerpts (significantly reorganized and with a lot of the redundancy and discussion of methodology removed) from the Discussion released by NOAA on October 19, 2017. 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 and Oceanic 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

A LA NINA WATCH CONTINUES, AS ATMOSPHERIC AND OCEANIC CONDITIONS, TAKEN IN TOTALITY, REMAIN CLOSEST TO ENSO-NEUTRAL CONDITIONS THROUGH EARLY OCTOBER. OCEANIC CONDITIONS CONTINUE TO MOVE QUITE CLOSE TO THE LA NINA STATE AS EQUATORIAL SEA SURFACE TEMPERATURE (SST) DEPARTURES FROM NORMAL ARE NEGATIVE TO A MAGNITUDE OF -0.5 DEGREES C FROM ABOUT 150W TO THE SOUTH AMERICAN COAST WITH A HORSESHOE OF ABOVE NORMAL SSTS TO THE NORTH AND SOUTH OF THIS REGION AND ACROSS THE FAR WESTERN PACIFIC (TYPICAL OF DEVELOPING/ESTABLISHED LA NINA CONDITIONS). OCEANIC HEAT CONTENT (OCEAN TEMPERATURES ACROSS THE PACIFIC BASIN FROM THE SURFACE TO 300 METERS DEPTH) SHOW A CONSIDERABLE RESERVOIR OF COLDER THAN NORMAL WATER, OFTEN A PRECURSOR FOR THE DEVELOPMENT OF MORE ESTABLISHED LA NINA CONDITIONS.

IN TERMS OF THE ATMOSPHERE, SUPPRESSED CONVECTION REMAINS OBSERVED ACROSS MUCH OF THE CENTRAL EQUATORIAL PACIFIC WHILE ENHANCED RAINFALL CONTINUES ACROSS THE MARITIME CONTINENT REGION. ALTHOUGH GENERALLY WEAK OVERALL, THE TRADE WINDS IN THE PACIFIC HAVE BEEN ENHANCED AND UPPER-LEVEL WESTERLY WIND ANOMALIES ARE CURRENTLY OBSERVED IN THE REGION AS WELL. AN ADDITIONAL FACTOR TO BE COGNIZANT OF IN THE COMING MONTH IS THE CURRENT DEVELOPING MJO WHICH HAS, AND WILL LIKELY CONTINUE TO, MODULATE SST, WINDS AND CONVECTION ON THE SUBSEASONAL TIME SCALE ACROSS THE PACIFIC BASIN AS IT PROGRESSES ACROSS THE PACIFIC TO THE WESTERN HEMISPHERE, AS CURRENTLY PREDICTED.

PROGNOSTIC DISCUSSION OF SST FORECASTS

THERE HAS NOT BEEN MUCH CHANGE TO PREDICTIONS OF EQUATORIAL PACIFIC SST ANOMALIES FROM LAST MONTH WITH MOST STATISTICAL AND DYNAMICAL MODEL SOLUTIONS HOVERING AROUND THE -0.5 DEGREES C THRESHOLD, GENERALLY TAKEN AS THE BOUNDARY FOR WEAK LA NINA CONDITIONS. SPECIFICALLY, THE CPC NINO3.4 SST CONSOLIDATION, WHICH OBJECTIVELY WEIGHTS STATISTICAL GUIDANCE (CCA, CA AND MARKOV) AND THE CFS, FORECASTS THE NINO3.4 SST ANOMALY TO HOVER AT THE -0.5 DEGREES C VALUE THROUGH JFM 2018 BEFORE GRADUALLY REDUCING TOWARD AN ANOMALY NEAR ZERO BY AMJ 2018. THERE ARE CONSIDERABLE DIFFERENCES IN THE EVOLUTION OVER TIME OF THESE FORECASTS THIS MONTH, WITH THE CA, AS AN EXAMPLE, PREDICTING NEAR ZERO ANOMALY THROUGHOUT THE FORECAST PERIOD.

THE NMME SUITE OF MODELS FOLLOW THIS GENERAL THEME, ALTHOUGH THE PERIOD OF THE MOST NEGATIVE NINO3.4 SST ANOMALIES VARIES SOMEWHAT AS THE CFS REACHES THIS POINT DURING DJF 2017-18 WHILE THE GFDL MODEL DOES SO DURING OND 2017. THE ENSEMBLE MEAN PREDICTION IS QUITE CONSISTENT WITH THE CPC NINO3.4 SST CONSOLIDATED FORECAST, ALTHOUGH WITH SOMEWHAT MORE NEGATIVE TEMPERATURE DEPARTURES - REACHING -0.7 DEGREES C DURING DECEMBER 2017 AND JANUARY 2018. THE VARIATION AND IN SOME CASES THE INCREASE IN NINO3.4 SST ANOMALIES AT THE START OF THE PREDICTIONS IS RELATED SUBSEASONAL NOISE ASSOCIATED WITH THE ONGOING MJO EVENT.

30-DAY OUTLOOK DISCUSSION FOR NOVEMBER 2017

THE OUTLOOK FOR NOVEMBER 2017 IS DRAWN FROM A COMBINATION OF DYNAMICAL AND EMPIRICAL FORECAST TOOLS SPANNING SUBSEASONAL TO SEASONAL TIME SCALES. THE 0.5-MONTH LEAD MONTHLY OUTLOOK IS ALWAYS CHALLENGING BECAUSE OF THE UNCERTAIN INTERPLAY BETWEEN LOW-FREQUENCY VARIABILITY AND WEEK-TO-WEEK CLIMATE VARIABILITY. THIS PROBLEM IS NOW AMPLIFIED CONSIDERING THAT AUTUMN IS A PERIOD WHEN PREDICTABILITY OF SUBSEASONAL VARIABILITY IS RELATIVELY LOW AND THE EXTRATROPICAL RESPONSE TO ENSO IS NOT YET FULLY MATURE.  

A FIRST PASS AT THE NOVEMBER TEMPERATURE OUTLOOK MUST CONSIDER THE COMBINED EFFECTS OF ENSO AND LONG-TERM TRENDS. THIS MONTH THERE IS CONSTRUCTIVE INTERFERENCE OVER THE SOUTHWESTERN CONUS BETWEEN WARMING TRENDS AND THE LA NINA CLIMATE FOOTPRINT. CALIBRATED DYNAMICAL GUIDANCE ALSO YIELDS THE HIGHEST PROBABILITIES FOR ABOVE-NORMAL TEMPERATURES OVER THAT REGION, AND SO THE OFFICIAL FORECAST FAVORS ABOVE-NORMAL TEMPERATURES OVER MUCH OF THE SOUTHWESTERN CONUS. LONG-TERM TRENDS AND CALIBRATED MODEL GUIDANCE AGREE ON A SLIGHT TILT TOWARD ABOVE-NORMAL TEMPERATURES FOR PARTS OF THE NORTHEAST. OVER MUCH OF ALASKA, ESPECIALLY THE NORTH SLOPE, LONG-TERM TRENDS CONTINUE TO DOMINATE AND LEAD TO A FAIRLY CONFIDENT FORECAST IN FAVOR OF ABOVE-NORMAL TEMPERATURES.

OVER A LARGE SWATH OF THE COUNTRY, HOWEVER, SPANNING FROM THE ALASKA PANHANDLE TO THE NORTHWEST TO THE MIDWEST TO THE SOUTHEAST, EQUAL CHANCES OF ABOVE-, NEAR-, AND BELOW-NORMAL TEMPERATURES ARE FORECAST. THIS IS DUE TO CONFLICTING FORECAST SIGNALS AMONG VARIOUS TOOLS.  

IN THE VERY SHORT TERM, A HIGH AMPLITUDE PATTERN CHANGE IS FORECAST OVER NORTH AMERICA WITH A WEST-EAST RIDGE/TROUGH PATTERN FORECAST DURING THE 6 TO 10 DAY PERIOD. THIS PATTERN CHANGE MIGHT BE AMPLIFIED BY THE FORECAST RECURVATURE AND EXTRATROPICAL TRANSITION OF TYPHOON LAN OVER THE WEST PACIFIC. THIS IS LIKELY TO LEAD TO BELOW-NORMAL TEMPERATURES FOR A TIME OVER PARTS OF THE EASTERN HALF OF THE CONUS. HOWEVER, THE LATEST EXTENDED RANGE GUIDANCE FROM THE GLOBAL ENSEMBLE SYSTEMS SUGGESTS THAT THIS PATTERN IS MORE OR LESS TRANSIENT.  

THE LATEST FORECASTS FROM THE CFS FAVOR ABOVE-NORMAL TEMPERATURES ACROSS MOST OF THE CONUS, INCLUDING OVER AREAS OF THE CENTRAL CONUS WHERE THE MODEL HAS CONSIDERABLE HINDCAST SKILL. ADDITIONALLY, THE LATEST WEEKS 3-4 DYNAMICAL MODEL GUIDANCE FAVORS ABOVE-NORMAL TEMPERATURES FOR THE FIRST HALF OF THE MONTH OVER MOST OF THE NORTHERN TIER OF THE CONUS, BUT SLIGHTLY FAVORS BELOW-NORMAL TEMPERATURES OVER THE SOUTHEAST. COMPLICATING MATTERS IS AN ONGOING STRONG MJO EVENT THAT IS FORECAST TO PROPAGATE OVER THE FAR WESTERN PACIFIC DURING THE COMING TWO WEEKS. AN EMPIRICAL FORECAST MODEL THAT INCORPORATES THE MJO, ENSO, AND LONG-TERM TRENDS DEPICTS BELOW-NORMAL TEMPERATURES CENTERED OVER THE UPPER MIDWEST DURING THE FIRST HALF OF NOVEMBER. THIS DISCUSSION IS PROVIDED HERE TO GIVE SOME INSIGHTS INTO THE VARIOUS CONSIDERATIONS AND CONFLICTING CLIMATE SIGNALS THAT GO INTO A EC FORECAST.

THE PRECIPITATION OUTLOOK FOR NOVEMBER 2017 HAS LESS COVERAGE THAN THE TEMPERATURE FORECAST AND DRAWS MOSTLY ON THE LOW-FREQUENCY ENSO FOOTPRINT. GIVEN LARGE DISAGREEMENTS BETWEEN STATISTICAL AND DYNAMICAL GUIDANCE OVER MUCH OF THE CONUS, MODEST PROBABILITIES REFLECTING THE BACKGROUND CLIMATE STATE ARE MOST APPROPRIATE. ABOVE-NORMAL PRECIPITATION IS FAVORED OVER NORTHERN ALASKA WHICH IS CONSISTENT WITH LONG-TERM TRENDS.

PROGNOSTIC DISCUSSION OF OUTLOOKS - NDJ 2017 TO NDJ 2018

Three-Months NDJ 2017  -  2018 with consideration of Spring as well.

Temperature

THE NOVEMBER-DECEMBER-JANUARY (NDJ) 2017-18 OUTLOOK FAVORS ABOVE NORMAL TEMPERATURES FOR THE MAJORITY OF THE FORECAST DOMAIN, INCLUDING MUCH OF ALASKA. THE HIGHEST PROBABILITIES FOR ELEVATED ODDS OF WARMER THAN NORMAL TEMPERATURES ARE LOCATED ACROSS PORTIONS OF THE SOUTHWEST AND TEXAS. DURING THE WINTER MONTHS THROUGH FEBRUARY-MARCH-APRIL (FMA) 2018 SEASON, ENHANCED ODDS FOR BELOW NORMAL TEMPERATURES ARE HIGHLIGHTED IN VARYING AREAS OF THE NORTHERN CONUS, SOUTHEAST ALASKA AND THE ALASKA PANHANDLE, WHILE ABOVE NORMAL TEMPERATURES REMAIN FAVORED FOR MUCH OF THE WESTERN AND SOUTHERN CONUS, AND NORTHERN ALASKA.  

Precipitation

THE NDJ 2017-18 PRECIPITATION OUTLOOK INDICATES INCREASED CHANCES OF ABOVE NORMAL PRECIPITATION FOR WESTERN AND NORTHERN ALASKA, AS WELL AS AREAS OF THE NORTHERN AND CENTRAL ROCKIES. DURING NDJ 2017-18, BELOW NORMAL PRECIPITATION IS FAVORED ALONG THE SOUTHERN TIER OF THE CONUS, EXCLUDING SOUTHERN CALIFORNIA. AS WE MOVE THROUGH THE WINTER SEASON, ELEVATED ODDS FOR ABOVE NORMAL PRECIPITATION INCREASE IN COVERAGE FOR AREAS OF THE NORTHERN PLAINS, GREAT LAKES AND OHIO VALLEY THROUGH JANUARY-FEBRUARY-MARCH (JFM) 2018 AND THEN SLOWLY DECREASE ENTERING THE CORE SPRING MONTHS.

PROGNOSTIC TOOLS USED FOR U.S. TEMPERATURE AND PRECIPITATION OUTLOOKS

THE OFFICIAL TEMPERATURE AND PRECIPITATION OUTLOOKS FOR THE SEASONS FROM NDJ 2017-18 THROUGH FMA 2018 TOOK INTO CONSIDERATION IMPACTS OFTEN OBSERVED DURING LA NINA EVENTS AS THE LATEST OFFICIAL ENSO OUTLOOK AND NINO3.4 SST MODEL GUIDANCE CONTINUES TO INDICATE ELEVATED PROBABILITIES AS COMPARED TO CLIMATOLOGY FOR LA NINA CONDITIONS DURING THIS PERIOD. STATISTICAL MODEL FORECAST TOOLS SUCH AS REGRESSIONS ANCHORED TO THE CPC NINO3.4 SST CONSOLIDATION FORECAST AND THE CCA U.S. TEMPERATURE AND PRECIPITATION PREDICTIONS ALONG WITH DYNAMICAL MODEL GUIDANCE FROM THE NMME SUITE OF MODELS, BOTH IN DETERMINISTIC AND CALIBRATED PROBABILISTIC FORM, CONTRIBUTED HEAVILY TO THE OUTLOOK. LONG TERM TRENDS IN BOTH TEMPERATURE AND PRECIPITATION WERE ALSO UTILIZED QUITE STRONGLY IN SOME AREAS IN THE OUTLOOKS. THE CA U.S. TEMPERATURE AND PRECIPITATION PREDICTIONS WERE ONLY USED AT INTERMEDIATE AND LATER LEADS AS ITS ENSO FORECAST WAS VIEWED AS SOMEWHAT OF AN OUTLIER AS COMPARED TO THE REMAINING NINO3.4 SST GUIDANCE EARLY IN THE PERIOD.

TEMPERATURE

THE UPDATED SET OF TEMPERATURE OUTLOOKS THIS MONTH DO INDICATE SOME SUBSTANTIAL CHANGES FROM THE PRECEDING SET OF OUTLOOKS DURING THE WINTER SEASONS PRIMARILY ACROSS THE NORTHERN CONUS AND SOUTHEAST AREAS OF ALASKA INCLUDING THE ALASKA PANHANDLE. INCREASING PROBABILITIES FOR LA NINA (AS INDICATED IN OBSERVATIONAL DATA AND THE MOST RECENT SET OF MODEL FORECASTS) AS WELL AS STATISTICAL AND DYNAMICAL FORECAST TOOLS THAT IN LARGE PART ARE CONSISTENT WITH TYPICAL LA NINA IMPACTS ESPECIALLY THOSE OBSERVED IN THE MORE RECENT PORTION OF THE AVAILABLE RECORD ARE A STRONG CONTRIBUTION TO THE TEMPERATURE OUTLOOK EVOLUTION FROM NDJ 2017-18 THROUGH FMA 2018. LONG TERM TRENDS IN MANY AREAS ALSO PLAYED A CONSIDERABLE ROLE IN THE OUTLOOK EVOLUTION AT NEARLY ALL FORECAST LEADS. OUTLOOKS FROM SUMMER 2018 WERE PRIMARILY DRIVEN BY LONG TERM TRENDS AND THE CONSTRUCTED ANALOGUE STATISTICAL TOOL AFTER ANY CONSIDERATIONS FOR RESIDUAL LA NINA IMPACTS ARE ANTICIPATED TO END.

THE NDJ 2017-18 TEMPERATURE OUTLOOK IS LARGELY UNCHANGED FROM THE OUTLOOK RELEASED LAST MONTH AND DEPICTS ELEVATED ODDS FOR ABOVE NORMAL TEMPERATURES FOR MOST OF THE FORECAST DOMAIN. THE MAIN CHANGE WAS A DECREASE IN COVERAGE IN FAVORED ABOVE NORMAL TEMPERATURES FOR PORTIONS OF SOUTHERN ALASKA. AS WE EVOLVE THROUGH THE WINTER SEASON THROUGH FMA 2018, HOWEVER, AN ENHANCED LIKELIHOOD OF BELOW NORMAL TEMPERATURES IS HIGHLIGHTED FIRST FOR PORTIONS OF SOUTHEAST AREAS OF ALASKA INCLUDING THE PANHANDLE, THE FAR PACIFIC NORTHWEST TO THE FAR NORTHERN PLAINS. DURING JFM AND FMA 2018, BELOW NORMAL TEMPERATURES ARE FAVORED FOR AN AREA IN THE MIDWEST AND WESTERN GREAT LAKES. THE ADDITIONS ARE BASED AS A RESULT OF A CONVERGENCE OF TOOL SUPPORT FROM TYPICAL LA NINA IMPACTS, TEMPERATURE PREDICTIONS BASED ON REGRESSION WITH THE CPC NINO3.4 SST CONSOLIDATION PREDICTION AND LONG TERM TRENDS AS PREDICTORS AND CONSISTENT, TO FIRST ORDER, FORECASTS FROM SEVERAL SHORT TERM CLIMATE DYNAMICAL MODEL GUIDANCE FROM THE NMME PARTICIPANT MODELS AND ITS ENSEMBLE MEAN IN BOTH DETERMINISTIC AND CALIBRATED PROBABILISTIC FORMATS. ALSO, RECENT LONGER TERM TEMPERATURE TRENDS IN THE GREAT LAKES REGION AND MIDWEST, AS CHARACTERIZED BY 15 YEAR OCN METHODOLOGY, ARE NEGATIVE AND CONTRIBUTE TO THE OUTLOOK AS WELL.  

THE REMAINING OUTLOOKS FROM MJJ 2018 ONWARD THROUGH NDJ 2018-19 ARE PRIMARILY BASED ON LONGER TERM TEMPERATURE TRENDS THAT CAN BE STRONG AND REASONABLY PREDICTABLE IN MANY AREAS OF THE CONTIGUOUS U.S. AND ALASKA. ALONG WITH TRENDS, PREDICTIONS FROM THE NEAR GLOBAL SST BASED CONSTRUCTED ANALOGUE TOOL ALSO CONTRIBUTED TO THE OUTLOOKS.

PRECIPITATION

FOR PRECIPITATION, THE OUTLOOKS ARE TO FIRST ORDER SIMILAR TO THE SET OF OUTLOOKS RELEASED LAST MONTH WITH THE PRIMARY DIFFERENCE IN MOST CASES, AN INCREASE IN FORECAST COVERAGE AND IN SOME CASES AN INCREASE IN FORECAST PROBABILITIES. PROGRESSING FROM THE NDJ 2017-18 PERIOD THROUGH THE WINTER, ELEVATED ODDS FOR ABOVE NORMAL PRECIPITATION, INITIALLY HIGHLIGHTED IN THE NORTHERN ROCKIES, EXPAND IN COVERAGE TO INCLUDE PARTS OF THE NORTHERN PLAINS, MIDWEST, GREAT LAKES AND OHIO VALLEY. DRIER THAN AVERAGE CONDITIONS ARE FAVORED ACROSS THE SOUTHERN TIER OF THE CONUS WITH THE GREATEST PROBABILITIES IN DJF 2017-18 AND JFM 2018 IN SOME AREAS OF THE SOUTHEAST. AGAIN, IN MOST PARTS OF THE REGIONS DEPICTED, ALTHOUGH THE PROBABILITIES ARE MODEST, FORECASTS REFLECT WHERE THERE IS A PREPONDERANCE OF EVIDENCE FROM BOTH STATISTICAL FORECAST TOOLS, DYNAMICAL MODEL OUTPUT AND IN SOME REGIONS NON-TRIVIAL LONG TERM, BOTH POSITIVE AND NEGATIVE, PRECIPITATION TRENDS.

THE PRECIPITATION OUTLOOKS FROM AMJ 2018 ONWARD THROUGH OND 2018 WERE GENERALLY UNCHANGED FROM THE OUTLOOKS PREPARED LAST MONTH. THESE FORECASTS ARE HIGHLIGHTING GENERALLY SMALL REGIONS WHERE LONG TERM PRECIPITATION TRENDS ARE EVIDENT AND WHERE HISTORICAL CROSS VALIDATED PREDICTION SKILL HAS BEEN SHOWN TO BE POSITIVE.

Forecasting the Evolution of ENSO

El Nino Probabilities used by NOAA in Their Forecast (The forecast for the value of the Nino 3.4 Index receives the most attention).

Below is the latest NOAA forecast of Nino 3.4 temperature anomalies.  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 sea surface temperatures.

Here is the NOAA forecast for the Nino 3.4 Index.

CFSv2 Forecast as of October 20, 2017

I have added a blue line at -0.5C which is the level that defines La Nina Sea Surface Conditions in the Nino 3.4 Measurement Area. This level needs to be maintained or exceeded on the downside for five consecutive overlapping three-month periods to constitute a La Nina not just a period of La Nina Conditions. In the above graphic, the required duration may be barely met over the period from mid October through FMA 2018. But it does not last that long in some other models that NOAA uses. It does not last that long in many International forecasting models. So it is a judgment call at this point in time.

I am using the below NOAA image in addition to the image that updates daily because it also shows the sea surface temperature forecast for the entire Equatorial Pacific. Red is a warm anomaly. For an El Nino forecast the model would be showing red along the Equator in the Eastern Pacific and the model is not projecting that but instead we see what is called a cold tongue in blue extending from Ecuador. Those images are a bit small I agree. But the Equator is marked and so is the Coast of South America. It is a little tricky but you can find larger images here. Track across the top row labeled SST Normalized with Skill Mask and click on the E3 which is the latest forecast. Each of the images can also be clicked on to enlarge.

 CFS.V2 SST Forecast October 16, 2017September 18, 2017

It is now showing a La Nina for Fall and Winter. You can see the cold tongue extending from Ecuador in the maps on the right.

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

As you can see there has been in the past week a slight shortening of the La Nina duration perhaps. FMA 2018 is where the timing of the transition back to Neutral is in dispute.

Here is the IRI Discussion:

IRI Technical ENSO Update Published: October 19, 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-October 2017, the NINO3.4 SST anomaly was near the borderline of the weak La Niña category. For September the SST anomaly was -0.47 C, in the upper portion of the ENSO-neutral range, and for July-September it was -0.07 C, in the 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 -0.5, at the borderline of ENSO-neutral and weak La Niña. The pertinent atmospheric variables, including the upper and lower level zonal wind anomalies, have been showing patterns suggestive of near-La Niña, and the Southern Oscillation Index (SOI) has also been somewhat above average. Subsurface temperature anomalies across the eastern equatorial Pacific are somewhat below average. Despite recent SST anomalies and some clear signs of La Niña patterns in some key atmospheric variables, the combination of the SST and the atmospheric conditions continues to warrant an official diagnosis of ENSO-neutral for the recent 1-month period.

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 fall and into winter, with slightly lower chances for ENSO-neutral. A La Niña watch was issued with that Discussion, for the second consecutive month. The latest set of model ENSO predictions, from mid-October, now available in the IRI/CPC ENSO prediction plume, is discussed below. Those predictions suggest that the SST has the greatest chance for being in the weak La Niña range for October-December through January-March 2017, with a slightly lower but significant probability for ENSO-neutral during that period.

As of mid-October, about 65 to 70% of the dynamical or statistical models predicts La Niña conditions from the initial Oct-Dec 2017 season through to the Jan-Mar 2018 season. During this period, about 30 to 35% of models predict neutral conditions, while no models predicts El Niño 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 Jan-Mar 2018 season, among models that do use subsurface temperature information, 33% of models predicts neutral conditions and 67% predicts La Niña conditions. For all models, at longer lead times reaching through the first half of 2018, predictions for ENSO-neutral conditions dominate, with probabilities from 70% to higher levels, except for the final season of Jun-Aug 2018 when the probability for El Niño rises to 35% and for La Niña decreases to near zero.

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 65 and 70% from Oct-Dec to Dec-Feb, with 30-35% probabilities for neutral conditions during these seasons and near-zero probabilities for El Niño. Probabilities for ENSO-neutral rise to approximately 75% during Mar-May and Apr-Jun when the likely La Niña conditions are expected to have returned to neutral. For the longer lead forecasts for Apr-Jun to Jun-Aug 2018, chances for El Niño rise to 32% by the final season as chances for neutral remain greater than 50% and for La Niña decrease to 15-20%. 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 Oct-Dec 2017 to Jan-Mar 2018, with neutral regaining highest probability status from Feb-Apr through the end of the forecast period in summer 2018. Chances for El Niño are very small through Mar-May 2018, rising to near-climatological probabilities for May-Jul and slightly higher for Jun-Aug 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 in early June [Editor's Note: I believe they mean early November and this sentence seems to often not be updated] by CPC and IRI, which will include some human judgement in combination with the model guidance.

A look at the subsurface along the Equator is very useful.

July 11, 2017 Equatorial Temperature Anomalies. Sepember 15, 2017 Subsurface Water Temperatures Equatorial Ocean Subsurface as of october 15, 2017

I have "frozen" these three charts. The one on the left shows the situation three months ago. The one on the right shows the situation now.  The situation is a lot different now than three months ago but similar to the situation last month. There is now no warm water on the surface between 170W and 120W which is where ENSO is measured. Three months ago there was a lot. We predicted that given that three months ago there was not much warm water to the west of 170W that the situation would change and indeed it has. Notice that currently there is a lot of cold water at depth. We have not discussed it in this report but the Easterlies when strong move surface water west which causes subsurface water to move to the surface. The SOI is part of the equation here as the SOI has now signaled that the Easterlies will tend to persist aside from periodic interruptions by the Active Phase of the MJO.

Upper Ocean Heat Content October 15, 2017

Above is a larger version of the graphic on the right in the set of three graphics. It is the current situation. One might notice that there cool area is not a bit fragmented and closer to the surface and to the wast there is a bit more warm water.

Upper Ocean heat Content October 15, 2017

This pretty much integrates the temperature of the water in the area of measurement across the various pods of warmer and cooler water...we are talking about anomalies not absolute temperatures. It may be that the overall negative temperature anomaly has peaked and is starting to moderate. That is a natural process and suggests that the life of this cool event is limited.

It could well be that the every ten year adjustment adjustment mechanism NOAA uses for the base climatology of the Tropical Pacific for real time analysis (OISSTv2 data set) is not able to keep up with Ocean Warming which may slightly overstate warm anomalies. Even the five year adjustment they use to review the data for historical analysis (ERSSTv4) really does not help very much when there is a trend that is either a secular trend due to Global Warming or part of a sixty-year low-frequency cycle such as the PDO. Current values tend to be higher than the average.

Here is the current October 1, 2017 JAMSTEC forecast for the Nino 3.4 Index.

October 1, 2017 JAMSTEC Forecast

There has since last month been a significant change in the JAMSTEC forecast of the Nino 3.4 Index  It is now fairly consistent with the NOAA forecast but the NOAA forecast is more suggestive that this cool event will have sufficient duration to be declared a La Nina and will reach a lower level of the Nino 3.4 index. The JAMSTEC forecasted Index is not low enough for long enough to be declared an official La Nina (-0.5C or lower) but it is is close and it continues to be a negative value through the forecast period way into 2019. The fairly minor differences between the various Nino 3.4 forecasts have a large impact on the seasonal outlooks of the two Agencies. 

Here is the discussion from JAMSTEC:

Oct. 20, 2017: Prediction from 1st Oct., 2017

ENSO forecast:

The weak La Niña-like condition will persist until boreal spring of next year. Then the tropical Pacific will return to a normal state by summer.

Indian Ocean forecast:

The weak positive Indian Ocean Dipole will disappear by December. The tropical Indian Ocean is expected to return to a normal state by spring of next year.

Regional forecast:

On a seasonal scale, most part of the globe will experience a warmer-than-normal condition, while some parts of West Africa, India and northern Brazil will experience a colder-than-normal condition in boreal winter.

As regards to the seasonally averaged rainfall, a wetter-than-normal condition is predicted for some parts of East Africa, Philippine, and northern Brazil during boreal winter, whereas most parts of Indonesia, Australia, West Africa, Europe, western U.S, and southern Brazil will experience a drier condition during boreal winter. Those are partly due to the weak La Niña-like condition and the weak positive Indian Ocean Dipole.

In late fall and winter, most parts of Japan will experience warmer- and drier-than-normal conditions.

Here is the Nino 3.4 report from the Australian BOM (it normally updates every two weeks but this copy is frozen to prevent it from updating after this article is published).

Australia POAMA ENSO model run October 8, 2017

Discussion Issued October 9, 2017

The El Niño–Southern Oscillation (ENSO) remains neutral. The surface of the tropical Pacific has warmed over the past fortnight as a result of weaker trade winds. This has reversed the cooling trend that had been observed since mid-winter. While sea surface temperatures remain well within the neutral range, anomalously cool water persists below the surface.

International climate models surveyed by the Bureau suggest this recent surface warming may only be temporary, with further cooling of the tropical Pacific Ocean likely. Five of the eight models suggest sea surface temperatures will reach La Niña thresholds by December 2017, but only three maintain values for long enough to be classified as a La Niña event.

While unusual, it is not unheard of to see La Niña develop this late in the year. Of the late-developing La Niña events, their effect on summer rainfall has been mixed, with some leading to widespread above-average falls across eastern Australia, and others having minimal effect. The current 3-month rainfall outlook suggests only a 50% likelihood of wetter conditions in many parts of the country.

The Australian BOM employs a different threshold for considering a SSTA to be either La Nina or El Nino. Note their forecast is showing ENSO Neutral based on their criteria through their forecast period. But it would meet the NOAA criteria for La Nina Conditions but it is marginal for having sufficient duration. 

Indian Ocean IOD (It updates every two weeks)

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

IOD POAMA Model Run October 8, 2017

Discussion Issued October 9

Indian Ocean Dipole outlooks

The Indian Ocean Dipole (IOD) is neutral. The weekly index value to 8 October was +0.05 °C.

Most of the climate models surveyed by the Bureau indicate that the IOD will remain neutral during spring. Three of the six models suggest a positive IOD remains a possibility during spring. A positive IOD is typically associated with below average spring rainfall over southern and central Australia.

IOD events typically decay during spring, and the influence of the IOD on Australian climate is weak during the months 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.

Thus both the NOAA and Australian BOM forecasts are signaling ENSO Cool with NOAA pretty much calling a La Nina and the September 1 JAMSTEC forecast shows near La Nina conditions for January 2018 while NOAA shows La Nina Conditions for January 2018.

Does the Atmosphere as measured by the SOI Index confirm that we have La Nina Condition?

SOI values as of October 20, 2017

Normally La Nina Conditions are confirmed by SOI 30 day values that are greater than or equal to +7.0.  El Nino Conditions are confirmed by SOI 30 day values that are less than or equal to -7.0. So right now both the Nino 3.4 Index and the SOI suggest that we are entering La Nina "Conditions". At this point no meteorological agency has felt compelled to declare that La Nina conditions currently exist but that could have soon.

Some believe the rate of change of the SOI Index is as important as the absolute value so notice the change from July through September and month to date in October.

The SOI Index is quite volatile. So even + or - 7.0 is not that significant. +  or - 20 means something.

SOI Index History

B. Now we begin our comparison of the NOAA and JAMSTEC Forecasts (Focus on next nine months i.e. three seasons)

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.

JAMSTEC works in three-month intervals which correspond to seasons and does not change the selection of months each time they update but does so every three months. At that time they drop one season and add another season further in the future. So for JAMSTEC we have Winter (DJF 2017-2018) Spring (MAM 2018) and Summer (JJA) to work with and we have the corresponding maps from NOAA so that we can compare the two. I show the NOAA Maps first followed by the JAMSTEC maps. I extract North America from the Worldwide JAMSTEC map and use that to compare with the NOAA Maps. I also extract Europe including parts of North Africa and Western Asia from the Worldwide JAMSTEC maps and include it in the summary table at the beginning of this article.

DJF 2017/2018 (Winter)

Temperature

NOAA

DJF 2017-2018 Temperature Issued by NOAA on october 19, 2017

And here is the DJF 2017/2018  temperature forecast for North America that I extracted from the JAMSTEC World Forecast

DJF 2017/2018 JAMSTEC Temperature extracted from Oct 1, 2017 World Forecast

These are fairly similar for CONUS but reversed for Alaska. JAMSTEC shows warmer for the Great Lakes Area.

And now the JAMSTEC WORLD FORECAST (for this graphic my comments are mostly related to areas other than Alaska and CONUS as those comments appear with the graphics above)

DJF 2017/2018 Temperature Forecast from JAMSTEC Oct 1, 2017 forecast.

For the World, JAMSTEC shows much of the world warm except for Africa and Northern South America and the CONUS Northwest and parts of Canada and most of India. Australia is mixed.

Precipitation

NOAA

NOAA NDJ 2017/2018 Precipitation Issued October 19, 2017

And here is the DJF 2017/2018 Precipitation Forecast for North America that I extracted from the JAMSTEC World Forecast.

North America DJF 2017/2018 Precipitation Extracted from Oct 1, JAMSTEC Forecast

A lot of similarity here but not identical for sure. The wet area in Alaska is different and the pattern in CONUS is as usual more north versus south for NOAA and more central versus west and east for JAMSTEC. It is a recurring pattern for NOAA to tend to show for CONUS North/South divisions and JAMSTEC to show West/East divisions or in this case a West/Central/East division. It will be interesting to see how things work out.

JAMSTEC WORLD FORECAST

DJF 2017/2018 Jamstec Precipitation Forecast From Oct 1, 2017

Of interest is the dry Europe and generally wet Southern Hemisphere. The dry Japan is also of interest.

Here is the precipitation forecast from Queensland Australia. It does not cover the same months but rather OND 2017:

Consistently Near Zeor SOI  forecast for October to December  2017.

It is kind of amazing that you can make a worldwide forecast based on just one parameter the SOI and changes in the SOI. In this graphic, CONUS looks like a north south divide with the southern tier wet. Eastern Africa is wet. Australia is slightly dry. This forecast will be updated on November 1 and since the SOI is not rising, the new forecast will be very different. I am showing the above mostly to show that one can make a forecast (that has a high level of accuracy) based on one index in this case the SOI.

MAM  (Spring)

Temperature

NOAA

MAM  2018 Temperature NOAA Issued on October 19, 2017September 21, 2017

And here is the MAM  2018 Temperature Forecast for North America that I extracted from the JAMSTEC World Forecast

MAM  2018 North American Temperature extracted from JAMSTEC Oct 1 Forecast

It is again fairly similar but JAMSTEC shows a much larger and western displaced cool anomaly and the view of Canada helps to put it in perspective. .

JAMSTEC WORLD FORECAST

MAM  2018 JAMSTEC Temp from Oct 1, 2017

For JAMSTEC we see a lot more cool areas in this season. Northern South America is cool plus much of Central America and is Northern and Eastern Australia plus part of the Middle East and scattered areas in Africa. 

Precipitation

NOAA

NOAA AM  2018 Precipitation Issued on October 19, 2017

And here is the MAM  2018 Precipitation Forecast for North America that I extracted from the JAMSTEC World Forecast

MAM  2018 JAMSTEC Precipitation for CONUS based on Oct 1 forecast

JAMSTEC has Alaska wet and has more dry area in CONUS especially the Southeast.

JAMSTEC WORLD FORECAST

MAM 2018 JAMSTEC Precipitation Forecast from Oct 1, 2017

Much of Eastern Europe is dry. Brazil is wet. Australia is mixed. Parts of India are dry. Equatorial Africa is dry but Southern Africa is wet. Japan is dry.

JJA 2018 (Summer)

Temperature

NOAA

NOAA JJA 2018 Temperature Issued October 19, 2017

And here is the JJA 2018 Temperature Forecast for North America that I extracted from the JAMSTEC World Forecast

JJA 2018 North America Temperature Forcast Extracted from the Oct 1 JAMSTEC Forecast

The pattern is similar but where NOAA shows EC, JAMSTEC shows cool and again the connection with Canada helps with the understanding.

JAMSTEC WORLD FORECAST

JJA 2018 JAMSTEC Temperature from Oct 1, 2017

The cool areas are Northeastern Siberia, The British Isles and part of Scandinavia, Northeastern South America and Mexico, and the Southern Tip of Africa and the Northern part of Australia and Eastern Asia. It is warm overall but not that extreme an imbalance.

Precipitation

NOAA

JJA 2018 Precipitation Issued October 19, 2017

And here is the JJA 2018 Precipitation Forecast for North America that I extracted from the JAMSTEC World Forecast

JAMSTEC JJA 2018 precipitation extracted from their Oct 1 2017 Forecast

NOAA shows only New England wet and JAMSTEC does not fully agree and shows a huge Southeast dry anomaly. JAMSTEC also shows Southern Alaska dry while NOAA has it EC. So this season is very divergent.

JAMSTEC WORLD FORECAST

JAMSTEC JJA 2018. Precipitation from 1 Oct 2017

Southern Europe continues to be dry with Scandinavia wet. India is dry. Central America is dry. Japan remains dry but most of Southeast Asia is wet, India is dry, the Maritime Continent is dry. You  can see the dry pattern in the Equatorial Pacific but not a wet tongue associated with an El Nino.

Conclusion

Both forecasts are based on ENSO being primarily negative with NOAA going all the way to a weak but short La Nina and JAMSTEC still in Neutral Territory but closer to NOAA than last month. The differences in the forecast maps are less than last month. But the NOAA forecast last month may not have fully reflected their Nino 3.4 forecast so part of their change this month might have been catch  up. Aside from the comparison of NOAA and JAMSTEC for Alaska and CONUS, JAMSTEC also provides a worldview that NOAA does not.

One value of doing this sort of analysis is that as the projected value of Nino 3.4 changes, we have the basis for extrapolating between these two sets of forecast maps if the Nino 3.4 forecasts come closer together. If they become farther apart, it may still be possible to make some reasonable guesses as to how this will impact weather.

Some Housekeeping Issues.

The next Regular Weekly Weather and Climate Report will be published on October 23. 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.

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

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