Written by Sig Silber
NOAA issued their Seasonal Outlook on May 18 and JAMSTEC issued theirs at least a week earlier than NOAA. There are significant differences in the two forecasts for the U.S. I also present the forecasts for the Rest of the World but cannot compare them to a NOAA forecast due to lack of available data. I provide separate maps for Europe. It is very important to understand these forecasts and track the development of a possible El Nino as the differences are very significant for the U.S. Europe, Asia, Australia and may impact world events in the Middle East.
 
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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 evolution of a possible ENSO into Summer and Fall. JAMSTEC in their further-out forecast (which is out to Dec 2017 – Feb 2018) is reflecting a much higher probability of strong El Nino conditions this coming Fall into Winter.
Both the NOAA and ENSO forecasts are attempting to properly factor in the chances of an El Nino this Summer and into next winter. The difficulty with predicting an El Nino in May is discussed [click here ] This makes all forecasts right now beyond the next three months somewhat of a WAG. But I am surprised at the extent of the differences between the JAMSTEC probability of an El Nino and the NOAA estimates of the probability of an El Nino. Those probabilities have a big impact on the projected weather and the impact of that weather which we will discuss in this article. It is also important because we are watching for a possible Climate Shift in the Pacific to a period lasting two to three decades of PDO Positive. A strong El Nino this winter would be supportive of that Climate Shift taking place.
Some Housekeeping Issues
This report will be posted late Saturday May 20 and will be referred to in the Weekly Report for reference until the Saturday after the next NOAA Update on June 15, 2017 which we will report on June 17. The Regular Weekly Report will be published on May 22. 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.
Below is a quick 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 Summer, Fall into Winter. For some readers, these two sets of summary graphics may be all the information they wish to look at and that is fine.
Temperature
| Â | NOAA Alaska + CONUS | JAMSTEC North America | JAMSTEC Europe |
| JJA |  |  |  |
| SON |  |  |  |
DJF 2017/2018 |  |  |  |
Precipitation
| Â | NOAA Alaska + CONUS | JAMSTEC North America | JAMSTEC Europe |
| JJA |  |  |  |
| SON |  |  |  |
DJF 2017/2018 |  |  |  |
NOAA Updated Seasonal Outlook
NOAA issued their updated Seasonal Outlook on the third Thursday of the month i.e. May 18, 2017 as is their normal schedule. Let’s first take a look at the NOAA maps. Then we will compare the NOAA Maps to those issued by JAMSTEC. 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 June 2017. It is called the Early Outlook because it will be updated at the end of May. Only the June Outlook will be updated at that time.
Temperature
Precipitation
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 June maps from the April 20, NOAA Report to compare against. And May is not over so we can not really compare the June forecast against May actual. It is probably best to just try to understand what NOAA is trying to convey about June which can be summarized as warm around the perimeter and wet in the Rocky Mountains where it also is likely to be cool.
Now we consider the three-month Outlook.
Notice that the three-month periods are abbreviated e.g. June/July/August is shown as JJA. You will see such abbreviations often in this report.
Prior Temperature Outlook for JJA 2017
New Temperature Outlook for JJA 2017
Prior Precipitation Outlook for JJA 2017
New Precipitation Outlook for JJA 2017
Now let us focus on the long-term situation and compare the new set of maps with the maps issued on May 18, 2016.
Prior 14 Month Temperature Outlook: JJA 2017 – MJJ 2018
New 14 Month Temperature Outlook: JAS 2017 – JJA 2018
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:
Prior 14 Month Precipitation Outlook: JJA 2017 – MJJ 2018
New 14 Month Precipitation Outlook: JAS 2017 – JJA 2018
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          Â
One can mentally subtract the June Outlook from the three-month Outlook and create the Outlook for the last two months in the three-month period namely July and August 2017. To do that you need to take into account that:
* 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 some of the redundancy removed) from the Discussion released by NOAA on May 18, 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
OCEANIC AND ATMOSPHERIC OBSERVATIONS ACROSS THE EQUATORIAL PACIFIC AS A WHOLE INDICATE ENSO-NEUTRAL CONDITIONS ARE CONTINUING. THE LATEST WEEKLY SST ANOMALY MAP INDICATES THAT WEAKLY POSITIVE SST ANOMALIES EXIST ACROSS NEARLY THE ENTIRE EQUATORIAL PACIFIC BASIN, WITH HIGHER AMPLITUDE ANOMALIES LOCATED NEAR THE SOUTH AMERICAN COAST. THE HEAT CONTENT ANOMALY OF THE UPPER-OCEAN LAYERS, TO A DEPTH OF 300 METERS, SUMMED ACROSS THE BASIN FROM THE DATE LINE TO 100W HAS REBOUNDED FROM THE DECREASE OBSERVED LAST MONTH AND IS NOW POSITIVE.
IN THE ATMOSPHERE OVER THE PAST MONTH, LOWER TROPOSPHERIC ZONAL WIND ANOMALIES WERE WEAK. OVER THE SAME PERIOD, MEASUREMENTS OF TROPICAL CONVECTION INDICATED THE DEVELOPMENT OF ENHANCED CONVECTION JUST SOUTH OF THE EQUATOR WITH WEAKLY ENHANCED CONVECTION CONTINUING OVER THE MARITIME CONTINENT. THIS COMBINATION OF THE ATMOSPHERIC AND OCEANIC EVOLUTION SUGGESTS A SHIFT FURTHER AWAY FROM THE REMNANT LA NINA BASE STATE.
ENSO-NEUTRAL CONDITIONS PERSISTED DURING APRIL, WITH NEAR-AVERAGE SEA SURFACE TEMPERATURES (SSTS) OBSERVED ACROSS THE CENTRAL EQUATORIAL PACIFIC, AND ABOVE-AVERAGE SSTS IN THE FAR EASTERN PACIFIC. A RESERVOIR OF SUBSURFACE WARMTH CONTINUES TO BE OBSERVED NEAR THE DATE LINE, CENTERED AT A DEPTH OF ABOUT 150 METERS. MAXIMUM TEMPERATURE ANOMALIES RANGE FROM ABOUT 3-5 DEGREES C ABOVE-AVERAGE. LOW-LEVEL (850-HPA) WIND ANOMALIES AVERAGED CLOSE TO NORMAL DURING THE PAST 30-DAYS. FOR THE SAME TIME PERIOD, THE OUTGOING LONGWAVE RADIATION (OLR) PATTERN (WHICH SERVES AS A PROXY FOR CONVECTIVE ANOMALIES ACROSS THE TROPICAL PACIFIC) DEPICTED AN AREA OF ENHANCED CONVECTION SOUTH OF THE EQUATOR FROM ABOUT 160E TO 125W, OR FROM ABOUT THE SOLOMON ISLANDS EASTWARD ACROSS THE SOUTH PACIFIC TO THE PITCAIRN ISLANDS. SUPPRESSED CONVECTION WAS NOTED ROUGHLY WITHIN THE SAME LONGITUDE BAND, THOUGH NORTH OF THE EQUATOR. THIS OLR FIELD IS NOT REPRESENTATIVE OF EITHER AN EL NINO OR A LA NINA.
PROGNOSTIC DISCUSSION OF SST FORECASTS
THE CPC NINO 3.4 SST INDEX CONSOLIDATION FORECAST, WHICH INCLUDES CANONICAL CORRELATION ANALYSIS (CCA), CONSTRUCTED ANALOG (CA), AND MARKOV STATISTICAL FORECASTS, ALONG WITH THE CFS DYNAMICAL MODEL, PREDICTS A MEDIAN TEMPERATURE ANOMALY OF BETWEEN +0.4C AND +0.5C FOR THE COMING SEASONS FROM APPROXIMATELY JJA THROUGH NDJ 2017, WITH EL NINO AS MOST LIKELY FROM LATE SUMMER THROUGH AUTUMN. THE CFS HAS BACKED OFF ITS EL NINO FORECAST IN A FAIRLY DRAMATIC FASHION OVER THE PAST MONTH, WHILE THE CA STATISTICAL FORECAST HAS BECOME THE WARMEST CONSTITUENT MEMBER OF THE CONSOLIDATION FORECAST. THE LATEST FORECASTS FROM THE DYNAMICAL SUITE OF MODELS FROM THE NMME CONTINUE TO FAVOR EL NINO DEVELOPMENT, THOUGH NOT AS STRONGLY AS LAST MONTH. THE LATEST OFFICIAL ENSO OUTLOOK FROM CPC/IRI PLACES THE ODDS OF EL NINO AND ENSO NEUTRAL AT ROUGHLY 45% FROM JJA THROUGH DJF. THE CONSENSUS FORECAST INDICATES THE LIKELIHOOD OF A REPEAT LA NINA EVENT TO BE SMALL DURING THIS FORECAST PERIOD.
30-DAY OUTLOOK DISCUSSION FOR JUNE 2017 Â
THE MADDEN-JULIAN OSCILLATION (MJO) WAS ACTIVE SINCE LATE APRIL, WITH THE ENHANCED CONVECTIVE PHASE CURRENTLY OVER THE INDIAN OCEAN. DURING THE NEXT TWO WEEKS, THE MJO IS FORECAST TO EXHIBIT EASTWARD PROPAGATION ACROSS THE INDIAN OCEAN AND MARITIME CONTINENT, BUT WITH VERY LOW AMPLITUDE. THEREFORE, THE MJO IS NOT LIKELY TO PLAY A SIGNIFICANT ROLE IN THE MONTHLY VARIABILITY OVER NORTH AMERICA DURING JUNE. ANTECEDENT SOIL MOISTURE WAS ALSO CONSIDERED FOR THE JUNE TEMPERATURE AND PRECIPITATION OUTLOOKS. SOIL MOISTURE IS ANOMALOUSLY HIGH OVER PORTIONS OF THE MIDWEST, AND SOUTH-CENTRAL PARTS OF BOTH THE MISSISSIPPI VALLEY AND GREAT PLAIN REGIONS. AT THIS TIME OF YEAR, THERE IS A SIGNIFICANT NEGATIVE CORRELATION BETWEEN SURFACE TEMPERATURE AND PRECIPITATION IN THIS GENERAL AREA; THAT IS, RELATIVELY COOL AND WET CONDITIONS OFTEN GO HAND-IN-HAND.
Temperature
DYNAMICAL MODELS FROM THE NMME SUITE GENERALLY INDICATED ABOVE-NORMAL MEAN TEMPERATURES FOR PORTIONS OF THE WESTERN, SOUTHERN, AND EASTERN CONUS, AND FOR MUCH OF WESTERN ALASKA. PROBABILISTIC AND CALIBRATED VERSIONS OF THE NMME TOOL WERE CONSIDERED FIRST-GUESS FIELDS FOR THE JUNE OUTLOOK. THE UNCALIBRATED NMME TEMPERATURE FORECAST APPEARED TO BE TOO WARM ACROSS THE MIDWESTERN STATES, WHERE CALCULATED SOIL MOISTURE RANKING PERCENTILES WERE EASILY IN EXCESS OF 70-80 PERCENT. THE CFS, THE CANADIAN MODEL (CMC1 CANCM3), AND THE NASA MODEL PREDICTED BELOW-NORMAL TEMPERATURES OVER PORTIONS OF THE NORTHERN AND CENTRAL ROCKIES, AND CENTRAL AND SOUTHERN PLAINS. THE OFFICIAL TEMPERATURE OUTLOOK FOR JUNE INCLUDES AN AREA OF FAVORED BELOW-NORMAL TEMPERATURES OVER MUCH OF WYOMING AND COLORADO, ESPECIALLY IN LIGHT OF THE NEGATIVE TEMPERATURE-PRECIPITATION CORRELATIONS NOTED EARLIER, AND THE FACT THAT THE ONE PRECIPITATION SIGNAL THAT IS CONSIDERED RELIABLE IS THE AREA OF PREDICTED ABOVE-MEDIAN PRECIPITATION OVER THIS SAME GENERAL REGION. OTHER MODEL SOLUTIONS, SUCH AS THOSE FROM GFDL AND NCAR, APPEAR TO BE TOO BULLISH ON THEIR PREDICTION OF NEARLY COAST-TO-COAST WARMTH ACROSS THE CONUS. IN WESTERN ALASKA, MOST (BUT NOT ALL) OF THE NMME SUITE PREDICTS ABOVE-NORMAL TEMPERATURES. RELATIVELY WARM SSTS, AND THE UNUSUALLY LARGE EXPANSE OF OPEN (ICE-FREE) WATER WEST AND SOUTHWEST OF BARROW BY MID-MAY, FAVOR ABOVE-NORMAL TEMPERATURES FOR THE WESTERN PORTION OF THE NORTH SLOPE.
Precipitation
THE JUNE PRECIPITATION OUTLOOK ALSO USES THE PROBABILISTIC AND CALIBRATED VERSIONS OF THE NMME AS ITS STARTING POINT. THE ONLY SIGNAL WHICH APPEARED RELIABLE IS AN AREA OF EXPECTED ABOVE-MEDIAN PRECIPITATION OVER THE VICINITY OF THE ROCKIES, AND CENTRAL AND SOUTHERN PLAINS. THE CFS, IMME, CANADIAN MODEL (CMC2 CANCM4), AND TO A LESSER DEGREE THE NASA MODEL, LEND SUPPORT FOR THIS WET SIGNAL. IN CONTRAST, THE GFDL FLOR MODEL PREDICTS BELOW-MEDIAN PRECIPITATION ACROSS THIS PART OF THE CONUS, WHILE THE GFDL CM2.1 AND NCAR MODELS PREDICT SOMETHING IN-BETWEEN THE TWO EXTREMES. ELSEWHERE, WHICH INCLUDES A LARGE PORTION OF THE CONUS AND ALL OF ALASKA, PRECIPITATION SIGNALS ARE EITHER TOO WEAK OR TOO INCOHERENT TO BE OF MUCH USE.
Three to Four Month June, July, August and Possibly September
Temperature
THE LATEST JJA AND JAS 2017 TEMPERATURE OUTLOOKS INDICATE ABOVE-NORMAL TEMPERATURES ARE MOST LIKELY FOR MUCH OF THE FORECAST DOMAIN, WITH THE EXCEPTION OF PARTS ROCKIES AND PLAINS. THE CHANCES OF ABOVE-NORMAL SEASONAL MEAN TEMPERATURES ARE SLIGHTLY ENHANCED FOR MUCH OF THE PACIFIC NORTHWEST, BUT THE PROBABILITY OF ABOVE-NORMAL TEMPERATURES IS MODERATED BY RECENT POSITIVE SNOW AND SOIL MOISTURE ANOMALIES. ABOVE-NORMAL TEMPERATURES ARE PARTICULARLY ENHANCED FOR A REGION STRETCHING FROM THE SOUTHWEST, EASTWARD ACROSS THE FAR SOUTHERN TIER OF THE CONUS INTO THE EASTERN U.S. THE GREATEST PROBABILITIES EXCEED 50% FOR PARTS OF THE SOUTHWEST AND ALONG THE GULF AND ATLANTIC COASTS, FOLLOWING THE CALIBRATED PROBABILISTIC GUIDANCE FROM THE NMME. NEGATIVE SOIL MOISTURE ANOMALIES IN THE SOUTHEAST REGION ALSO CONTRIBUTE TO THE LIKELIHOOD OF ANOMALOUS WARMTH. DECADAL CLIMATE TRENDS ALSO SUPPORT THE OUTLOOK AND ARE A COMPONENT OF THE DYNAMICAL MODEL GUIDANCE. THESE FORECAST TOOLS ALSO SUPPORT ENHANCED PROBABILITIES OF ABOVE-NORMAL TEMPERATURES FOR ALASKA.
POSITIVE SOIL MOISTURE ANOMALIES, COMBINED WITH PROBABILITIES FAVORING ABOVE-MEDIAN PRECIPITATION, SUPPORT SOME EXPANSION OF THE RELATIVE TEMPERATURE WEAKNESS OVER PARTS OF THE ROCKIES AND PLAINS STATES FOR JJA AND JAS. Â ADDITIONALLY, ANTECEDENT TROPICAL AND EXTRATROPICAL SST BOUNDARY CONDITIONS MAY INDICATE SOME COMPONENT OF INTERANNUAL VARIABILITY THAT COULD DESTRUCTIVELY INTERFERE WITH LONGER TERM WARMING TRENDS OVER PARTS OF THE CENTRAL AND EASTERN CONUS. WHILE THE FORECAST STILL BROADLY FAVORS ABOVE-NORMAL TEMPERATURES, THE PROBABILITIES ARE NOT EXCEPTIONAL, AND INDEED THE NMME FORECAST AND THE OFFICIAL FORECAST SUGGEST A SLIGHTLY COOLER FORECAST FOR THE CONUS AS A WHOLE THAN THAT ISSUED FOR LAST SUMMER FOR JJA AND JAS.
Precipitation
THE JJA 2017 PRECIPITATION OUTLOOK INDICATES ENHANCED PROBABILITIES OF ABOVE-MEDIAN PRECIPITATION FOR PARTS OF THE ROCKIES AND HIGH PLAINS, CENTERED EAST OF THE CONTINENTAL DIVIDE, EXTENDING SOUTHWARD THROUGH THE SOUTHERN PLAINS. ABOVE-MEDIAN PRECIPITATION IS ALSO SLIGHTLY FAVORED FOR PARTS OF MAINLAND ALASKA.
Longer Term Sept 2017 Through June/July/Aug 2018
AS THE FORECAST PROGRESSES TOWARD THE COLD SEASON, A SLIGHT TILT TOWARD EL NINO (RELATIVE TO LA NINA) IS INDICATED BY THE LATEST OBJECTIVE GUIDANCE AND EXPERT ASSESSMENTS. THIS HAS A SMALL IMPACT ON THE TEMPERATURE AND PRECIPITATION FORECASTS FOR THE SEASONS SPANNING SON 2017 THROUGH FMA 2018.
PROGNOSTIC TOOLS USED FOR U.S. TEMPERATURE AND PRECIPITATION OUTLOOKS
THE PRIMARY TOOLS USED FOR THIS SET OF SEASONAL OUTLOOKS INCLUDED BOTH STATISTICAL AND DYNAMICAL MODEL FORECAST GUIDANCE, AND IN PARTICULAR AT LONGER LEADS, DECADAL TEMPERATURE AND PRECIPITATION TRENDS. THE CALIBRATED DYNAMICAL MODEL GUIDANCE FROM THE NORTH AMERICAN MULTI-MODEL ENSEMBLE (NMME) AND, TO LESSER EXTENT, ITS INDIVIDUAL MODELS, INCLUDING THE NCEP CFS, WERE IMPORTANT CONTRIBUTORS TO THE OUTLOOKS THROUGH OND 2017. ANTECEDENT SOIL MOISTURE AND SNOWPACK ANOMALIES IN CERTAIN REGIONS ALSO IMPACTED THE OUTLOOKS AT EARLY LEADS. WHILE THE ENSO FORECAST REMAINS HIGHLY UNCERTAIN, THE SLIGHT TILT TOWARD EL NINO WAS CONSIDERED IN THE TEMPERATURE AND PRECIPITATION FROM SON THROUGH FMA.
PROGNOSTIC DISCUSSION OF OUTLOOKS – JJA 2017 TO JJA 2018
TEMPERATURE Â
SUBTLE CHANGES WERE MADE TO LATER LEADS, FROM ASO TO FMA, BASED ON THE LATEST MODEL GUIDANCE AND STATISTICAL FORECASTS THAT EMPHASIZE A SLIGHT TILT TOWARD EL NINO IMPACTS. GENERALLY THIS IS SEEN AS A SLIGHT INCREASE IN PROBABILITIES FAVORING ABOVE-NORMAL TEMPERATURE ACROSS THE NORTHERN TIER OF THE CONUS, AND A REDUCTION OF THE SAME ACROSS THE FAR SOUTHERN TIER.
HIGH PROBABILITIES FOR ABOVE-NORMAL TEMPERATURES ARE INDICATED FOR THE NORTH SLOPE OF ALASKA DURING SON AND OND 2017 DUE TO DECADAL TRENDS IN THE SEASONAL CYCLE OF SEA ICE.
PRECIPITATION
FROM ASO THROUGH OND 2017, INCREASING CHANCES FOR EL NINO CONDITIONS AND DYNAMICAL MODEL FORECASTS OF GREATER THAN AVERAGE SSTS IN THE EASTERN TROPICAL PACIFIC LEAD TO A SOUTHWARD SHIFT OF THIS REGION OF LIKELY ABOVE-MEDIAN PRECIPITATION INTO THE SOUTHWEST CONUS, EXTENDING ACROSS THE FAR SOUTHERN TIER OF THE CONUS WITH STILL MODEST PROBABILITIES.
FOR LATE AUTUMN AND WINTER, FROM NDJ 2017-2018 THROUGH JFM 2018, THE LOW PROBABILITY OF A LA NINA AND ELEVATED CHANCES FOR A POSSIBLE EL NINO NOW RESULT IN THE INTRODUCTION OF PROBABILITIES ASSOCIATED WITH A CANONICAL EL NINO, ALBEIT AT VERY LOW AMPLITUDE AND COVERAGE DUE TO THE HIGH UNCERTAINTY. FOLLOWING JFM 2018, WEAK SIGNALS DUE TO DECADAL TRENDS IN PRECIPITATION ARE INDICATED, INCLUDING BELOW-MEDIAN PRECIPITATION FOR PARTS OF THE SOUTHWEST BEGINNING WITH THE MAM 2018 SEASON AND ABOVE-MEDIAN PRECIPITATION IN THE NORTHERN-CENTRAL CONTIGUOUS U.S. BEGINNING WITH MAM 2018.
OVER ALASKA, CALIBRATED DYNAMICAL GUIDANCE FAVORS A SHIFT TOWARD ABOVE-MEDIAN PRECIPITATION FOR PARTS OF THE MAINLAND DURING THE EARLY LEADS. DURING SON, MODEST PROBABILITIES FAVORING ABOVE-MEDIAN PRECIPITATION ARE INTRODUCED OVER SOUTHERN ALASKA TO ACCOUNT FOR THE TILT TOWARD EL NINO; THAT SIGNAL CONTINUES IN THE FORECASTS THROUGH JFM 2018.
Forecasting the Evolution of ENSO
Here 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.
The question now is will the Warm Event that is taking place meet El Nino Standards?
A look at the subsurface is very useful.
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 remain in the ENSO Neutral phase 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).
And now we have the IRI/CPC May 18, 2017 fully model-based report. This (click to read) is the discussion that was issued with the May 18 Report (the graphic is on the right) and also the less formal mostly based on a Meteorologist survey a week earlier shown on the left.
Here is the most recent Nino 3.4 report from the Australian BOM.
Here is the recently released JAMSTEC forecast of the Nino 3.4 values. Notice they are forecasting a fairly high level for the Nino 3.4 Index (higher than the other Meteorological Agencies) but a rapid decline starting just prior to January. That is very significant relative to their DJF 2017 – 2018 forecast since some believe that the trend in the Nino 3.4 Index is as important as the absolute value. JAMSTEC’s forecast for the Nino 3.4 Index is of course subject to change next month.
The ENSO forecasts are not the only factor that is considered when making these fairly long-term forecasts but it is a very major factor so that ENSO forecast strongly influences the Temperature and Precipitation forecasts.
Now the Comparison of the NOAA and JAMSTEC Forecasts. I am only discussing the differences for Alaska and 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. I should note that JAMSTEC believes their model is most accurate at low latitudes. This makes sense as they would reasonably focus on Japan which is at about the same latitude as CONUS (the contiguous part of the United States in North America).
JAMSTEC works in three-month intervals and does not change the selection of months each time they update. So we have JJA, SON and DJF 2018, to work with from JAMSTEC and the same are available from NOAA. That means that this is the one out of every three months where the comparison can be made starting with the immediate three-month period.
JJA
Temperature
NOAA
And here is the forecast for North America that I extracted from the JAMSTEC World Forecast
And Now the JAMSTEC WORLD FORECAST
Precipitation
NOAA
And here is the forecast for North America that I extracted from the JAMSTEC World Forecast
JAMSTEC WORLD FORECAST
SON 2017
Temperature
NOAA
And here is the forecast for North America that I extracted from the JAMSTEC World Forecast
JAMSTEC WORLD FORECAST
Precipitation
NOAA
And here is the forecast for North America that I extracted from the JAMSTEC World Forecast
JAMSTEC WORLD FORECAST
DJF 2017-2018
Temperature
NOAA
And here is the forecast for North America that I extracted from the JAMSTEC World Forecast
JAMSTEC WORLD FORECAST
Precipitation
NOAA
And here is the forecast for North America that I extracted from the JAMSTEC World Forecast
JAMSTEC WORLD FORECAST
Conclusion
Both forecasts are based on an El Nino or Near-El Nino arriving. JAMSTEC assumes a stronger El Nino than NOAA and their forecast reflects this. In general an El Nino is a drought pattern for most of the World but not the U.S. The JAMSTEC forecast is simply more committed to a strong El Nino than is NOAA.
