Written by Sig Silber
A key index regarding seasonal weather forecasting is the Nino 3.4 Index which measures sea surface temperatures (SST) in a particular part of the Eastern Pacific. NOAA forecasts a moderate increase to El Nino levels (already there) and a fairly constant level for at least two seasons (I do not have a longer forecast from NOAA). JAMSTEC forecasts a fairly step rise early in 2019 and a steady decline for four seasons.
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There is a lag between El Nino Conditions along the Equator and impacts on CONUS. But the difference assessment of the Nino 3.4 Index (JAMSTEC is I believe correct on this) may explain the substantially different forecasts described in this report. But the fact that I think that JAMSTEC has a better grasp of the Nino 3.4 forecast does not mean I prefer their weather forecast to that of NOAA. Only time will tell who was more correct and JAMSTEC is a World forecast so they may be correct about a lot of places but not necessarily CONUS.
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.
We previously published Part I of this report which included all of the NOAA maps that were issued on December 20, 2018. The full report can be accessed here but what we have below may be sufficient for most readers. The full report contains a longer-term forecast but much of that is repeated in this report via the comparison with JAMSTEC.
| Temperature | Precipitation | |
| January |  |  |
| Three Months |  |  |
The three-month drought forecast map was also issued. A drought forecast for January only will be issued on the last day of December which is just two days from now. When issued, we will update this report to include that forecast.
This report is organized into a summary that has two tables of graphics that show the temperature and precipitation forecasts for the upcoming three seasons, A brief discussion of the ENSO assumptions by both NOAA and JAMSTEC and then the NOAA and JAMSTEC Agency discussions and then a comparison of the two forecasts which is basically an expansion of the summary table.
Summary of the NOAA and JAMSTEC Forecasts
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 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 | |
Winter JAMSTEC DJF 2018 – 2119 NOAA JFM 2019 |
|  |  |
Spring Temp MAM |  |  |  |
Summer Temp JJA 2019 |  |  |  |
Precipitation
| NOAA Alaska Plus CONUS | JAMSTEC North America | JAMSTEC Europe | |
Winter JAMSTEC DJF 2018 – 2119 For NOAA JFM 2019 |
|  |  |
Spring MAM 2019 |  |  |  |
Summer JJA 2019 |  |  |  |
It is useful to look at the forecasts for the Nino 3.4 Index used to determine if the Sea Surface Temperatures meet the criteria for an El Nino. Here is a brief summary of the Indices of the two Agencies and how they compare.
| One Year | JAMSTEC Two Years | |
| JAMSTEC |
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| CFS.v2 | CPC-IRI Probabilities | |
| NOAA |  |  |
| Which one of the above did NOAA use? They usually use the early meteorologist forecast but the model forecast that comes out later was available but was it used? The NOAA Discussion suggests the earlier forecast was used. |
Indices use a single number to convey information. Sometimes it is useful to look at the forecast Sea Surface Temperatures that correlate to the indices. I believe that these SST’s directly correlated with the JAMSTEC model but NOAA uses a variety of tools so it is not so easy to understand exactly how they do their forecast but there is a lot of information on that in their lengthy discussion which is presented shortly.
| NOAA | JAMSTEC |
 |  |
 | For completeness I show to the left a DJF forecast made by NOAA in early December, I do not see a significant difference between that graphic and the one above it. |
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 | To the left is the NOAA MAM 2019 SST forecast made in Early December. You can see their forecast was for a bit stronger El Nino at that time but not much different than their current forecast. They did not have a JJA forecast at that time. |
 |  |
Updates from JAMSTEC can be found here. Updates from NOAA can be found here. You have to look for the SST row and go to the right where it says “normalized with mask” and click on E3 which provides the latest model run.
All of these forecasts depend to a large extent on what is known about subsurface temperature anomalies. Here is the latest analysis.
Now let us examine the extent to which the atmosphere has responded to the warming Eastern Pacific.
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).
We see a lot of difference There may be some difference in duration but there clearly is a difference in both the maximum intensity and the pattern of the intensity with NOAA being lower and more even and JAMSTEC showing a pattern of a rapid rise and a slow but extended decline. The difference in the forecasts shows up in all three seasons. We go into that later in the report.
A. Focus on the NOAA Update (We presented the maps from NOAA Forecast in our Part I Report Published on December 21 which can be accessed here). But we did not present the NOAA Official Discussion at that time as I wanted to study it first.
Below are excerpts (slightly reorganized and with a bit of the redundancy and discussion of methodology removed) from the Discussion released by NOAA on December 20, 2018. 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 new NOAA Summary for DJF, and then the
- Atmospheric and Oceanic Conditions, and then
- The Initial Month (January in this case), and finally
- the remainder of the 15 Month Forecast.
We have in the past reorganized some of the material to consolidate it into the first three months of the forecast. The new NOAA Summary is not very detailed but it performs that function. Overall the NOAA forecast discussion has shown continual improvement in being a very useful read.
SUMMARY OF THE OUTLOOK FOR NON-TECHNICAL USERS
THE JANUARY-FEBRUARY-MARCH (JFM) 2019 TEMPERATURE OUTLOOK FAVORS ABOVE NORMAL TEMPERATURES THROUGHOUT THE WESTERN CONUS WITH THE HIGHEST ODDS (ABOVE 60 PERCENT) ACROSS THE PACIFIC NORTHWEST. THESE HIGH ODDS FOR ABOVE NORMAL TEMPERATURES EXTEND NORTH TO THE ALASKA PANHANDLE. A SLIGHT TILT IN THE ODDS FOR BELOW (ABOVE) NORMAL TEMPERATURES IS FORECAST ACROSS THE UPPER OHIO VALLEY, TENNESSEE VALLEY AND SOUTHERN APPALACHIANS (SOUTH FLORIDA). THE EXPECTATION FOR A HIGHLY VARIABLE TEMPERATURE PATTERN DURING THE 3-MONTH PERIOD RESULTS IN A FORECAST OF EQUAL CHANCES (EC) OF BELOW-, NEAR-, OR ABOVE-NORMAL TEMPERATURES ACROSS A MAJORITY OF THE EASTERN CONUS AND CENTRAL TO SOUTHERN GREAT PLAINS.
THE JFM 2019 PRECIPITATION OUTLOOK INDICATES ENHANCED ODDS OF ABOVE NORMAL PRECIPITATION AMOUNTS FOR THE SOUTHWEST, SOUTHERN GREAT PLAINS, GULF COAST, SOUTHEAST, AND PARTS OF THE MID-ATLANTIC. ABOVE-NORMAL PRECIPITATION IS ALSO FAVORED FOR SOUTHERN ALASKA AND THE ALASKA PANHANDLE. THE MOST LIKELY AREAS FOR BELOW NORMAL PRECIPITATION INCLUDE THE OHIO VALLEY AND THE PACIFIC NORTHWEST. EC IS FORECAST AMONG AREAS WHERE SEASONAL ACCUMULATED PRECIPITATION AMOUNTS ARE EXPECTED TO BE SIMILAR TO CLIMATOLOGICAL PROBABILITIES.
CURRENT ATMOSPHERIC AND OCEANIC CONDITIONS
OCEANIC OBSERVATIONS (FOR THE WEEK CENTERED ON 12 DECEMBER 2018) INDICATE ABOVE AVERAGE SEA SURFACE TEMPERATURES (SST) OF MORE THAN +1 DEGREE C ALONG THE EQUATOR, FROM 170E TO NEAR THE SOUTH AMERICA COAST. ABOVE-NORMAL SUB-SURFACE TEMPERATURES PERSIST AT DEPTH ACROSS THE CENTRAL AND EASTERN EQUATORIAL PACIFIC. THE LATEST WEEKLY ONI VALUE, BASED ON SST DEPARTURES FROM AVERAGE IN THE NINO 3.4 REGION, IS +1.1 DEGREES C.
DESPITE THE OCEANIC OBSERVATIONS SUPPORTING EL NINO, THE ATMOSPHERIC OBSERVATIONS THROUGH NOVEMBER 2018 REMAIN CONSISTENT WITH ENSO-NEUTRAL CONDITIONS WITH INTRA-SEASONAL VARIABILITY ASSOCIATED WITH THE MADDEN-JULIAN OSCILLATION (MJO) REMAINING THE MAJOR INFLUENCE. DURING EARLY TO MID-DECEMBER, NEGATIVE OLR ANOMALIES WERE OBSERVED FROM THE DATE LINE NORTHEAST TO THE SOUTHERN TIER OF THE CONUS. SINCE OCTOBER 2018, THE MADDEN-JULIAN OSCILLATION (MJO) WAS QUITE ROBUST WITH ITS ALTERNATING PHASES CROSSING THE PACIFIC OCEAN. DUE IN PART TO THE ACTIVE MJO, THE 850-HPA WINDS WERE NEAR AVERAGE ACROSS THE EQUATORIAL PACIFIC. THE ENHANCED PHASE OF THE MJO IS FORECAST TO PROPAGATE EAST FROM THE MARITIME CONTINENT TO THE PACIFIC OCEAN DURING LATE DECEMBER 2018 AND EARLY JANUARY 2019. THIS EVOLUTION OF THE MJO IS EXPECTED TO PLAY A ROLE IN THE CIRCULATION PATTERN AND TEMPERATURES ACROSS THE MID-LATITUDES OF NORTH AMERICA DURING JANUARY 2019.
PROGNOSTIC DISCUSSION OF SST FORECASTS
THE CPC SST CONSOLIDATION FORECAST, WHICH INCLUDES THREE STATISTICAL FORECASTS ALONG WITH THE CFS MODEL, PREDICTS A WEAK EL NINO, WITH SST ANOMALIES OF SLIGHTLY ABOVE +0.5 DEGREES C, CONTINUING THROUGH APRIL-MAY-JUNE 2019. THE NORTH AMERICAN MULTI MODEL ENSEMBLE (NMME) ENSEMBLE MEAN FORECAST FOR THE NINO-3.4 SST ANOMALY IS SLIGHTLY LESS THAN THE PREVIOUS MONTH, WITH ANOMALIES AT OR BELOW +1 DEGREE C. BASED ON THE LATEST OBSERVATIONS AND MODEL FORECASTS, THE OFFICIAL CPC/IRI ENSO OUTLOOK (AS OF EARLY DECEMBER) INDICATES A GREATER THAN 80 PERCENT CHANCE OF EL NINO DURING JFM 2019 AND 70 PERCENT THAT IT PERSISTS THROUGH MARCH-APRIL-MAY 2019.
PROGNOSTIC TOOLS USED FOR U.S. TEMPERATURE AND PRECIPITATION OUTLOOKS
THE TEMPERATURE AND PRECIPITATION OUTLOOKS WERE BASED ON DYNAMICAL MODEL GUIDANCE WHICH INCLUDED THE CFS ALONG WITH THE NMME AND ITS CALIBRATED PROBABILITIES THROUGH MAY-JUNE-JULY 2019. THE IMME WAS USED THROUGH APRIL-MAY-JUNE 2019. STATISTICAL FORECAST MODELS SUCH AS THE COMBINED ENSO-OCN TOOL, THE CONSTRUCTED SST ANALOG, AND CCA WERE ALSO INPUTS. INITIAL CONDITIONS SUCH AS COASTAL SSTS PLAYED A MINOR ROLE IN THE EARLIER LEADS. LONG-TERM TRENDS WERE WEIGHED MORE HEAVILY IN THE LATER OUTLOOKS, FROM SUMMER 2019 THROUGH THE 2019-20 WINTER.
CLIMATE EFFECTS TYPICALLY ASSOCIATED WITH EL NINO DURING THE WINTER AND SPRING WERE ALSO CONSIDERED. THE MJO IS EXPECTED TO REMAIN A MAJOR CONTRIBUTOR TO ANOMALOUS TROPICAL CONVECTION AND ITS ASSOCIATED INTERACTION WITH THE MID-LATITUDE CIRCULATION PATTERN, ESPECIALLY DURING JANUARY 2019. UNCERTAINTY REMAINS ON HOW MUCH BLOCKING AT THE HIGH LATITUDES DEVELOPS LATER IN JANUARY AND ITS LONGEVITY WITH LIMITED CONFIDENCE ON THE FUTURE EVOLUTION OF THE ARCTIC OSCILLATION (AO) AND NORTH ATLANTIC OSCILLATION (NAO).
30-DAY OUTLOOK DISCUSSION FOR JANUARY 2019 (This will be updated on December 31 which is just two days from now)
THE MONTHLY TEMPERATURE AND PRECIPITATION OUTLOOKS ARE BASED ON DYNAMICAL MODELS (MONTHLY NMME SUITE OF FORECASTS WHICH INCLUDES THE CFS, THE IMME, AND THE WEEK 3/4 ECMWF AND CFS FORECASTS), STATISTICAL MODELS (SMLR, CCA, OCN, CAS), ENSO, THE MJO, SSTS NEAR THE U.S. COAST, CONSIDERATION OF BOTH THE NORTH PACIFIC OSCILLATION (NPO) AND ARCTIC OSCILLATION (AO), AND CLIMATOLOGY.
THE LATEST ENSO UPDATE INDICATES ENSO-NEUTRAL CONTINUED DURING NOVEMBER. DESPITE ABOVE AVERAGE SSTS AND SUBSURFACE TEMPERATURES ACROSS MOST OF THE TROPICAL PACIFIC, THERE IS NO CLEAR COUPLING BETWEEN ATMOSPHERIC CONVECTION AND THE ABOVE AVERAGE OCEAN TEMPERATURES. THE LONG TRANSITION FROM ENSO-NEUTRAL TO EL NINO IS EXPECTED TO FINALLY GIVE WAY TO EL NINO, AND THEN CONTINUE THROUGH THE NORTHERN HEMISPHERE WINTER (90% CHANCE) AND THROUGH SPRING (ABOUT A 60% CHANCE). THEREFORE, EL NINO IS EXPECTED TO PLAY A ROLE IN THE JANUARY 2019 TEMPERATURE AND PRECIPITATION PATTERNS.
THE MJO IS CURRENTLY ROBUST, WITH THE ENHANCED CONVECTIVE PHASE OVER THE MARITIME CONTINENT REGION (PHASES 4 AND 5). DURING THE NEXT FEW WEEKS, THIS ENHANCED PHASE IS FORECAST TO MOVE OUT OVER THE WESTERN PACIFIC (PHASES 6 AND 7). THE CONVECTIVE PHASE OVER THIS LATTER REGION IS OFTEN ASSOCIATED WITH ANOMALOUSLY COLD WEATHER OVER THE CENTRAL AND EASTERN CONUS, PERHAPS BY MID JANUARY 2019.
THE NORTH PACIFIC OSCILLATION (NPO) AND ITS RELATED WEST PACIFIC OSCILLATION (WPO) ARE CURRENTLY IN THEIR POSITIVE PHASE. THIS PHASE IS CHARACTERIZED BY BELOW NORMAL SEA-LEVEL PRESSURE AND MID-TROPOSPHERIC HEIGHTS OVER THE ALASKA DOMAIN, AND ABOVE NORMAL SEA-LEVEL PRESSURE AND MID-TROPOSPHERIC HEIGHTS OVER THE MID-LATITUDE CENTRAL AND EASTERN PACIFIC. THIS SETUP IS TYPICALLY ASSOCIATED WITH ANOMALOUS WARMTH OVER MUCH OF NORTH AMERICA, AS RELATIVELY MILD PACIFIC AIR OVERSPREADS A LARGE PORTION OF THE CONTINENT. HOWEVER, IT IS THOUGHT THAT BY MID TO LATE JANUARY 2019, THE PHASE OF THE NPO COULD REVERSE, WHICH FAVORS THE FORMATION OF CONTINENTAL ARCTIC AIR MASSES OVER WESTERN CANADA. FROM THERE, IT’S ONLY A MATTER OF TIME BEFORE THESE ARCTIC AIR MASSES ADVANCE SOUTHEASTWARD INTO THE CENTRAL AND EASTERN CONUS. THE ARCTIC OSCILLATION (AO) IS ANOTHER KEY PLAYER REGARDING U.S. WINTERTIME CLIMATE VARIABILITY. THE GFS ENSEMBLE MEAN PREDICTS THE AO WILL BE IN ITS NEGATIVE PHASE (ANOMALOUS COLD OVER MUCH OF THE EASTERN CONUS) FOR THE NEXT 7-10 DAYS. BEYOND THAT, THERE IS LARGE UNCERTAINTY IN THE PREDICTED PHASE OF THE AO, THOUGH A SLIGHT MAJORITY OF ENSEMBLE MEMBERS FAVOR THE NEGATIVE PHASE.
Temperature
THE OFFICIAL JANUARY 2019 TEMPERATURE OUTLOOK FAVORS ABOVE NORMAL TEMPERATURES OVER ALASKA, THE WESTERN CONUS, AND SOUTHERN FLORIDA. THIS IS SUPPORTED BY THE NMME MODEL SUITE, THE IMME, MOST CFS MODEL RUNS DURING THE PAST NINE DAYS, AND TO SOME DEGREE THE SMLR TOOL. TEMPERATURE TRENDS DURING THE PAST 15 YEARS FOR THIS TIME OF YEAR SUPPORT ABOVE NORMAL TEMPERATURES ACROSS THE WEST. BELOW NORMAL TEMPERATURES ARE FAVORED OVER THE INTERIOR SOUTHEAST, SOUTHERN OHIO VALLEY, AND THE VIRGINIAS. THIS AGREES WELL WITH THE WEEK 3/4 TEMPERATURE FORECASTS FROM THE CFS AND ESPECIALLY THE ECMWF. SEVEN OF THE LAST NINE RUNS OF THE CFS PREDICT NEAR NORMAL TEMPERATURES ACROSS THIS SAME GENERAL REGION, WITH THE EXCEPTION OF THE LATEST TWO RUNS, WHICH INTRODUCE SOME ABNORMAL COLD TO THE EAST. A FEW OF THE INPUT MODELS TO THE NMME (NCAR, NASA, AND GFDL) ALSO FAVOR THIS RELATIVE COLD, BUT THE EXACT LOCATION IS UNCLEAR. THE CMC1 AND CMC2 CANADIAN MODELS PREDICT BELOW NORMAL TEMPERATURES FARTHER WEST OVER THE MIDDLE AND LOWER MISSISSIPPI VALLEY. ELSEWHERE, EQUAL CHANCES (EC) OF BELOW, NEAR, AND ABOVE NORMAL TEMPERATURES ARE FAVORED.
Precipitation
THE PRECIPITATION OUTLOOK FOR JANUARY 2019 FAVORS ABOVE NORMAL PRECIPITATION FROM THE SOUTHERN PLAINS EASTWARD ACROSS THE GULF COAST STATES, INCLUDING ALL OF FLORIDA. THIS WETNESS IS SUPPORTED BY A MAJORITY OF NMME INPUTS, AND IS WHAT WOULD BE EXPECTED WITH AN EL NINO AND ITS ASSOCIATED SOUTHERN TIER STORM TRACK. THE CALIBRATED VERSION OF THE NMME DEPICTS THE MOST FAVORED AREAS FOR RELATIVE WETNESS ARE THE SOUTHERN HIGH PLAINS AND THE EASTERN GULF COAST REGION. THE IMME, ON THE OTHER HAND, PREDICTS NEAR TO BELOW NORMAL PRECIPITATION ACROSS THE PREDICTED REGION (SOUTHERN PLAINS EASTWARD ACROSS THE GULF COAST STATES, INCLUDING ALL OF FLORIDA). THE CFS HAS BEEN CONSISTENT IN PREDICTING ABOVE NORMAL PRECIPITATION OVER MUCH OF TEXAS AND FLORIDA. ABOVE NORMAL PRECIPITATION IS ALSO FAVORED OVER THE SOUTHERN THIRD OF MAINLAND ALASKA, WHICH IS CONSISTENT WITH AN EL NINO, THOUGH THIS IS NOT PREDICTED BY ALL MODELS. BELOW NORMAL PRECIPITATION IS FAVORED OVER THE PACIFIC NORTHWEST, NORTHERN CALIFORNIA, THE NORTHERN AND PORTIONS OF THE CENTRAL INTERMOUNTAIN REGION, AND PARTS OF THE NORTHERN ROCKIES. THIS IS STRONGLY SUPPORTED BY THE NMME, THE IMME (ALTHOUGH SHIFTED SOUTHWARD TO INCLUDE WESTERN OREGON AND ALL OF CALIFORNIA), AND THE CFS MODEL TO VARIOUS DEGREES. ODDS FAVOR BELOW NORMAL PRECIPITATION OVER THE OHIO VALLEY AND SOUTHERN GREAT LAKES REGION, WHICH IS PARTLY ATTRIBUTED TO TYPICAL EL NINO IMPACTS, THE CAS, A MAJORITY OF THE PAST 9 CFS RUNS, AND THE IMME. ELSEWHERE, EQUAL CHANCES (EC) OF BELOW, NEAR, AND ABOVE NORMAL PRECIPITATION IS FAVORED.
PROGNOSTIC DISCUSSION OF OUTLOOKS – JFM 2019 TO JFM 2020
TEMPERATURE
THE MOST CHALLENGING PART OF THE JFM 2019 TEMPERATURE OUTLOOK REMAINS ON WHETHER TO INCLUDE A FAVORED AREA FOR BELOW NORMAL TEMPERATURES ACROSS PARTS OF THE EASTERN CONUS. BASED ON THE PREDICTED EVOLUTION OF THE MJO DURING THE NEXT FEW WEEKS ALONG WITH WEEKLY FORECASTS FROM THE CFS AND ECMWF MODELS, A RETURN TO BELOW NORMAL TEMPERATURES IS EXPECTED FOR THIS REGION LATER IN JANUARY. HOWEVER, THE STRENGTH AND LONGEVITY OF THIS ANOMALOUS COLD IS UNCERTAIN. IF THE MJO REMAINS ROBUST AND CONTINUES TO CIRCUMNAVIGATE THE GLOBAL TROPICS THROUGH THE WINTER, THEN ABOVE-NORMAL TEMPERATURES MAY BECOME MORE PREVALENT LATER IN FEBRUARY AND INTO MARCH. THIS COULD OFFSET ANY BELOW NORMAL TEMPERATURES THAT OCCUR EARLIER IN THE 3-MONTH PERIOD. AS OF MID-DECEMBER, THE CFS MONTHLY FORECASTS INDICATE A PROGRESSION FROM A COLDER TO WARMER OUTCOME FROM JANUARY THROUGH MARCH 2019 WHICH IS CONSISTENT WITH THE MJO REMAINING ACTIVE DURING THE NEXT COUPLE OF MONTHS. RECENT DAILY RUNS OF THE CFS MODEL HAVE TRENDED TOWARDS A COLDER OUTCOME ACROSS THE EASTERN CONUS DURING JANUARY. A COUPLE OF DYNAMICAL MODELS (GFDL AND NASA) PREDICT NEGATIVE TEMPERATURE ANOMALIES DURING JFM 2019 OVER A WIDESPREAD AREA OF THE EASTERN AND SOUTHERN CONUS. BASED ON HIGHER FORECAST CONFIDENCE EARLY IN THE 3-MONTH PERIOD RELATED TO FORCING FROM THE MJO, SUPPORT FROM STATISTICAL TOOLS, AND EL NINO TEMPERATURE COMPOSITES, TEMPERATURES DURING JFM 2019 ARE MOST LIKELY TO AVERAGE BELOW NORMAL ACROSS THE UPPER OHIO VALLEY, TENNESSEE VALLEY, AND SOUTHERN APPALACHIANS. DUE TO THE LACK OF GOOD AGREEMENT AMONG THE DYNAMICAL MODELS, PROBABILITIES FOR BELOW NORMAL TEMPERATURES ARE TEMPERED.
THE EXPECTATION OF A HIGHLY VARIABLE TEMPERATURE PATTERN DURING THE 3-MONTH PERIOD RESULTS IN A FORECAST OF EQUAL CHANCES OF BELOW-, NEAR-, OR ABOVE-NORMAL ACROSS THE MAJORITY OF THE EASTERN CONUS ALONG WITH THE CENTRAL AND SOUTHERN GREAT PLAINS. THE NMME SUPPORTS A SLIGHT TILT IN THE ODDS FOR ABOVE NORMAL TEMPERATURES ACROSS THE FLORIDA PENINSULA, WHILE THE FAVORED AREA OF ABOVE NORMAL TEMPERATURES ACROSS THE UPPER MISSISSIPPI VALLEY IS BASED ON EL NINO TEMPERATURE COMPOSITES AND DYNAMICAL MODELS. THE HIGHEST CONFIDENCE IN THE TEMPERATURE OUTLOOK FOR JFM 2019 EXISTS ACROSS THE WESTERN CONUS AND ALASKA WHERE ENHANCED ODDS FOR ABOVE NORMAL TEMPERATURES ARE FORECAST. THIS HIGH CONFIDENCE IS BASED ON EXCELLENT MODEL AGREEMENT, CONSISTENCY FROM PREVIOUS MONTHS, AND LONG-TERM TRENDS.
THE TEMPERATURE OUTLOOK FOR FMA 2019 IS SIMILAR TO JFM ALTHOUGH THE AREA FOR BELOW NORMAL TEMPERATURES IS REMOVED AS THE EXPECTATION FOR A COLDER OUTCOME DURING JANUARY AND EARLY FEBRUARY TIMES OUT. THE MAJOR REVISION TO THE TEMPERATURE OUTLOOKS NEXT SPRING WAS TO DECREASE THE COVERAGE OF ABOVE NORMAL TEMPERATURES ACROSS THE CENTRAL AND SOUTHERN GREAT PLAINS. THIS REVISION IS CONSISTENT WITH INCREASED CHANCES OF ABOVE NORMAL PRECIPITATION FOR THESE AREAS. THE TEMPERATURE OUTLOOKS FROM MAM THROUGH MJJ 2019 FOR MOST OF THE FORECAST DOMAIN ARE BASED ON THE CALIBRATED PROBABILITY FORECASTS FROM THE NMME ALONG WITH TRENDS. BEGINNING DURING THE SUMMER 2019 AND THROUGH WINTER 2019-20, THE TEMPERATURE OUTLOOKS WERE BASED PRIMARILY ON TRENDS.
PRECIPITATION
THE JFM 2019 PRECIPITATION OUTLOOK IS BASED ON DYNAMICAL MODELS AND EL NINO PRECIPITATION COMPOSITES WITH ABOVE NORMAL PRECIPITATION FAVORED ACROSS THE SOUTHWEST, SOUTHERN GREAT PLAINS, GULF COAST, SOUTHEAST, AND PARTS OF THE MID-ATLANTIC. DYNAMICAL MODELS HAVE REMAINED CONSISTENT IN THIS SPATIAL COVERAGE FOR THIS 3-MONTH PERIOD. EL NINO PRECIPITATION COMPOSITES AND THE IMME SUPPORT INCREASED CHANCES OF BELOW NORMAL PRECIPITATION ACROSS THE OHIO VALLEY. A SLIGHT TILT IN THE ODDS FOR BELOW NORMAL PRECIPITATION IS FORECAST FROM THE PACIFIC NORTHWEST SOUTH TO NORTHERN CALIFORNIA WHERE A GOOD MODEL CONSENSUS EXISTS. LIKEWISE, DYNAMICAL MODELS SUPPORT ENHANCED ODDS FOR ABOVE NORMAL PRECIPITATION ACROSS SOUTHERN ALASKA AND THE ALASKA PANHANDLE. EQUAL CHANCES OF BELOW-, NEAR-, OR ABOVE-NORMAL PRECIPITATION ARE FORECAST FOR THE REMAINDER OF THE FORECAST DOMAIN DUE TO WEAK OR CONFLICTING SIGNALS AMONG THE PRECIPITATION TOOLS. BASED ON THE LATEST DYNAMICAL MODELS, A SLIGHT TILT IN THE ODDS FOR ABOVE NORMAL PRECIPITATION WAS EXPANDED FROM THE PREVIOUS OUTLOOK TO INCLUDE THE DESERT SOUTHWEST AND SOUTHERN CALIFORNIA DURING FMA AND MAM 2019. ALSO, COVERAGE AND PROBABILITIES FOR ABOVE NORMAL PRECIPITATION DURING THE SPRING WERE INCREASED ACROSS THE CENTRAL AND SOUTHERN GREAT PLAINS.
COVERAGE OF FAVORED AREAS FOR ANOMALOUS PRECIPITATION DECREASE DURING THE SUMMER AS FORECAST CONFIDENCE DIMINISHES WITH A WEAKENING SIGNAL AMONG TOOLS AND CONVECTIVE PRECIPITATION BECOMES MORE DOMINANT. DURING JJA AND JAS 2019, BELOW (ABOVE)-NORMAL PRECIPITATION FAVORED FOR THE NORTHWESTERN (NORTHEASTERN) CONUS RELATED TO HISTORICAL TRENDS.
We also have the brief JAMSTEC Discussion
Dec. 19, 2018 Prediction from 1st Dec., 2018
ENSO forecast:
As predicted earlier, El Niño/El Niño Modoki-like state has actually emerged in October. The SINTEX-F continues to predict a moderate El Niño event that reaches its peak in late winter. This El Niño looks a mixture of Modoki-type and canonical-type and its impact may be different from that of the canonical El Niño.
Indian Ocean forecast:
As predicted earlier, the positive Indian Ocean Dipole (IOD) has actually emerged in July and the amplitude was enhanced in September. The model predicts that the positive IOD will quickly decay in winter. The Ningaloo Niña off the west coast of Australia will reach its peak in early austral fall.
Regional forecast:
On a seasonal scale, SINTEX-F predicts that most part of the globe will experience a warmer-than-normal condition in boreal winter, while some parts of southern U.S.A., northeastern Brazil, eastern Russia, western China, northern Africa, and southeastern Europe will experience a colder-than-normal condition. In boreal spring, SINTEX-F predicts that most part of the Southern Hemisphere will experience a warmer-than-normal condition, while U.S.A., northeastern China, Eurasian Continent, northern India, eastern Europe, and U.K. will experience a colder-than-normal condition. As regards to the seasonally averaged rainfall in boreal winter, a wetter-than-normal condition is predicted for most part of the western coast of Canada, southeastern/western U.S.A., eastern Brazil, western part of southern Africa, eastern China, and northeastern India. In contrast, northeastern U.S.A., Central America, northern part of the South American Continent, northwestern Brazil, Australia, eastern part of southern Africa, Europe, eastern Russia, southern part of Southeast Asia, the Philippines, and western part of Indonesia will experience a drier-than-normal condition. We notice that Australia may continue to experience extremely drier than normal condition.
In boreal spring, a wetter-than-normal condition is predicted for most part of U.S.A., western part of the South American Continent, eastern part of southern Africa, East Asia, and Indonesia. In contrast, the western coast of Canada, Mexico, Central America, northern part of the South American Continent, Brazil, Australia, western part of southern Africa, West Africa, Southeast Asia, the Philippines, and southern part of India will experience a drier-than-normal condition. We notice that Australia may continue to experience drier than normal condition.
The model predicts most part of Japan will experience warmer and wetter-than-normal condition in winter and spring as a seasonal average.
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) but for NOAA we have JFM, Spring (MAM), and Summer (JJA) to work with. JAMSTEC only provides three sets of maps and they only change every three months. So one out of three months the first season lines up perfectly and this is not that month. In one month (this time) the JAMSTEC first season is already underway and in another month it starts one month out.
The timing of the forecasts is something to consider. NOAA releases their Seasonal Outlook on the third Thursday of the month so one expects that the material was compile perhaps two days earlier than the date when it is published. JAMSTEC does not have a consistent time for releasing their forecast but the Nino 3.4 forecasts are dated the 1st of the month. Their Nino Index graphic and their forecast maps are placed on their web site just before NOAA issues their Seasonal Outlook. So one is not sure that the “initial conditions” for both forecasts are the same. In a couple places in this report I attempt to deal with that potential slight different in the currency of the two forecasts. It is not possible for me to know exactly what information the two agencies used in the preparation of their forecasts. I have assured myself that this detail of the way the two forecasts are produced has not had a major impact this month.
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 those excerpted maps in the summary table at the beginning of this article.
Winter DJF 2018/2019 for JAMSTEC and JFM 2019 for NOAA.
Temperature
NOAA
And here is the DJF 2018/2019 temperature forecast for North America that I extracted from the JAMSTEC World Forecast.
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 larger graphics above)
Precipitation
NOAA
And here is the DJF 2018/2019 Precipitation Forecast for North America that I extracted from the JAMSTEC World Forecast.
JAMSTEC WORLD FORECAST
Spring (MAM – 2019)
Temperature
NOAA
And here is the MAM – 2019 Temperature Forecast for North America that I extracted from the JAMSTEC World Forecast.
JAMSTEC WORLD FORECAST
Precipitation
NOAA
And here is the MAM – 2019 Precipitation Forecast for North America that I extracted from the JAMSTEC World Forecast.
JAMSTEC WORLD FORECAST
Summer (JJA 2019)
Temperature
NOAA
And here is the JJA 2019 Temperature Forecast for North America that I extracted from the JAMSTEC World Forecast.
JAMSTEC WORLD FORECAST
Precipitation
NOAA
And here is the JJA 2019 Precipitation Forecast for North America that I extracted from the JAMSTEC World Forecast
JAMSTEC WORLD FORECAST
C. Progress of ENSO
We are not including this section this month but we have addressed it early in this report and it is addressed in some detail in the NOAA Discussion. We published an ENSO Update in conjunction with our Drought and Agriculture Report on December 13 and it can be accessed here. Sea Surface Temperatures (SST’s) are already at El Nino levels so there is not much point in looking at the forecasts as to if and when that will happen as it has happened
NOAA will be updating the January forecast at the end of this month and will be issuing an ENSO update on January 10, 2019. We will use that opportunity to go into more detail on the status of a possible El Nino which may be declared on January 10, 2019. Either way we will have something to say on that topic at that time.
