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posted on 17 June 2017

NOAA and JAMSTEC Issue their Seasonal Outlook Updates Sans El Nino

Written by Sig Silber

NOAA issued their Seasonal Outlook on June 15 and JAMSTEC issued most of theirs on June 13 so both forecasts are equally current. Both agencies had to scramble to remove El Nino from their forecast. The resulting outlook for CONUS by JAMSTEC is less wet than the forecast by NOAA for the first two three-month periods but wetter and cooler for DJF 2017 - 2018.

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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 and mostly related to the differing perspectives on the timing of the small rises and later large decline of the Nino 3.4 Index. JAMSTEC in their further-out forecast (which is out to Dec 2017 - Feb 2018) is reflecting a higher probability of weak El Nino conditions this coming Fall into Winter.

Some Housekeeping Issues.

On Wednesday we issued a Special Update that addressed one item namely the reduction of the probabilities for an El Nino as indicated by the Nino 3.4 forecast that JAMSTEC posted on Tuesday June 13. That report can be found here. The data in that report, in some cases further updated, is in this evening's report. The Special Update contains some other information on the ENSO Cycle that is not included in this report which follows its usual format. This report will be posted late Saturday June 17.  A link to this report and the above mentioned Special Update will appear in the Weekly Weather and Climate Report for reference until the Saturday after the next NOAA Update on July 20, 2017 which we will report on July 22. The next Regular Weekly Weather and Climate Report will be published on June 19. If you are reading this Update Report and wish to transfer to the Current Weather and Climate Report, Click Here for the list of Weather Posts. That link takes you to the archive of all weather articles written by Sig Silber so you can if the new Weekly Weather Report has been published go there or back to an earlier report but please keep in mind that the graphics in earlier reports in some cases auto-update and the text may no longer apply to the graphics shown. Remember, if you leave this page to visit links provided in this article, you can return by hitting your "Back Arrow", usually top left corner of your screen just to the left of the URL box.

Now we Begin Our Report

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

  NOAA Alaska + CONUS JAMSTEC North America JAMSTEC Europe

JAS    (NOAA)

JJA (JAMSTEC)

JJA US Temperature Issued on June 15, 2017, NOAA Forecast JJA Temperature Based on June 1, 2017 JAMSTEC Forecast JJA Europe Temperature JAMSTEC June 1, 2017 Forecast
SON SON US Temperature Issued by NOAA on June 1, 2017 SON NA Temperature based on JAMSTEC June 1, 2017 Forecast SON 2017 Europe Temperature based on JAMSTEC June 1, 2017 Forecast

DJF

2017/2018

DJF 2017-2018 Temperature Issued by NOAA on May 15, 2017 DJF NA Temperature based on June 1 JAMSTEC Forecast DJF Europe Temperature Based on June 1, 2017 Jamstec Forecast

 

Precipitation

  NOAA Alaska + CONUS JAMSTEC North America JAMSTEC Europe

JAS (NOAA)

JJA (JAMSTEC)

JAS US Precipitation Issued on June 15, 2017 NOAA Forecast JJA NA Precipitation Based on June 1, 2017 JAMSTEC Forecast JJA Europe JAMSTEC Precipitation May 1, 2017 Forecast
SON SON US Precipitation Based on June 1, 2017 Forecast SON NA Precipitation based on JAMSTEC June 1, 2017 Forecast SON 2017 Europe Precipitation based on JAMSTEC June 1, 2017 Forecast

DJF

2017/2018

DJF 2017 Precipitation based on June 15, 2017 NOAA forecast DJF US Precipitation based on June 1, JAMSTEC Forecast DJF Europe Precipitation Based on May 1, 2017 Jamstec Forecast

 

NOAA Updated Seasonal Outlook

NOAA issued their updated Seasonal Outlook on the third Thursday of the month i.e. June 15, 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 July 2017. It is called the Early Outlook because it will be updated at the end of June. Only the July Outlook will be updated at that time.

Temperature

July 2017 Early Temperature Report Issued on June 15, 2017

Precipitation

July 2017 Early Precipitation Outlook Issued on June 15, 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 July maps from the May 18, 2017, NOAA Report to compare against. And June is not over so we can not really compare the July forecast against July actual. It is probably best to just try to understand what NOAA is trying to convey about July which can be summarized as for temperature, it will be warm except in the Northwest which will be EC and with respect to precipitation, it is mostly EC with three wet anomalies one in far western Alaska, another mostly in Montana and a Western-Gulf-Coast wet anomaly. There is also a dry anomaly for the Central Rocky Mountain States.

Now we consider the three-month Outlook.

Notice that the three-month periods are abbreviated e.g. July/August/September is shown as JAS. You will see such abbreviations often in this report.

Prior Temperature Outlook for JAS 2017

JAS 2017 Temperature Outlook Issued May 18, 2017

New Temperature Outlook for JAS 2017

JJA 2017 Temperature Outlook Issued on June 15, 2017

There is not much change but the probabilities for warmer than climatology have decreased for parts of the Northwest and for parts of Texas and the Northern Plains EC area has withdrawn to the North and now only applies to Montana.

Prior Precipitation Outlook for JAS 2017

JAs 2017 Precipitation Outlook Issued on May 18, 2017

New Precipitation Outlook for JAS 2017

JJA 2017 Precipitation Outlook issued June 15, 2017

This is a big change with the Rocky Mountains wet anomaly withdrawing to the north and a Western Gulf Coast wet anomaly now appearing and the Alaskan wet anomaly withdrawing to the west. 

Now let us focus on the long-term situation and compare the new set of maps with the maps issued on June 15, 2017.

Prior 14 Month Temperature Outlook: JAS 2017 - JJA 2018

14 Month Temperature Outlooks Issued May 18, 2017

New 14 Month Temperature Outlook: ASO 2017 - JAS 2018

14 Month Temperature Outlook Issued on June 15, 207

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 changes are fairly minimal. In DJF 2017-2018 an EC anomaly develops in the North Central/Great Lakes area and continues throughout the remainder of the 14 month forecast. In the prior forecast this EC anomaly did not develop until MAM 2018. This probably is related to a faster decay of El Nino Conditions than assumed last month. Also a Mid-Atlantic cool anomaly shown last month to occur in JFM and FMA 2018 is no longer in the forecast.

Prior 14 Month Precipitation Outlook: JAS 2017 - JJA 2018

14 month Precipitation Outlooks Issued on May 18, 2017

New 14 Month Precipitation Outlook: ASO 2017 - JAS 2018

14 Month Precipitation Issued on June 15, 2017

For precipitation I will focus on the major changes. The most significant is the disappearance of the Southern Tier wet anomaly which last month showed from SON 2017 to DJF 2017-2018. This has been replaced by a Rocky Mountains wet anomaly for SON 2017 and OND 2017 which retreats to the south in NDJ 2017 to 2018 and the pattern then resembles a Southwest Summer Monsoon. Later in FMA 2018 it becomes a dry anomaly which is a month earlier than in the prior forecast. Again this reflects a faster progression of the ENSO event which NOAA now believes will be solidly ENSO Neutral sooner.

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 

July plus JAS 2017 Issued on June 15, 2017

One can mentally subtract the July Outlook from the three-month Outlook and create the Outlook for the last two months in the three-month period namely August and September 2017. To  do that you need to take into account that:

For temperature there is a reduction in the size of the CONUS Northwest EC anomaly in the three-month map as compared to the July Map. Thus if you assume these colors are assigned correctly, it is a simple algebra equation to solve August/September probability for a given location = (3XThree-Month Probability - July Probability)/2*. So you can derive the August/September forecast this way. You can do that calculation easily for where you live.
Re precipitation, there is  a Mid-Rocky Mountains cool anomaly shown in July but not in the three-month map. Thus if you assume these colors are assigned correctly, it is a simple algebra equation to solve August/September probability for a given location = (3XThree-Month Probability - July Probability)/2*. So you can derive the August/September forecast this way. You can do that calculation easily for where you live.

* 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 June 15, 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.

SUMMARY OF THE OUTLOOK FOR NON-TECHNICAL USERS

CURRENT ATMOSPHERIC AND OCEANIC CONDITIONS

OCEANIC AND ATMOSPHERIC OBSERVATIONS ACROSS THE EQUATORIAL PACIFIC INDICATE ENSO-NEUTRAL CONDITIONS PERSIST, ALTHOUGH SEA SURFACE TEMPERATURES (SSTS) ARE ABOVE AVERAGE IN THE EAST-CENTRAL PACIFIC OCEAN. THE OBSERVED WEEKLY SSTS ACROSS THIS REGION, CENTERED ON JUNE 7, FEATURE SMALL POSITIVE SST ANOMALIES OF 0.5 TO 1 DEGREE C FROM THE DATE LINE TO 130 DEGREES W. THE UPPER-OCEAN HEAT CONTENT ANOMALY FROM THE DATE LINE TO 100 DEGREES W REMAINS ABOVE AVERAGE BUT THE MAGNITUDE OF THIS ANOMALY DECREASED SINCE EARLY MAY.

DESPITE WARMER-THAN-AVERAGE OCEAN TEMPERATURES ACROSS THE CENTRAL AND EASTERN PACIFIC SINCE MARCH, ATMOSPHERIC CONVECTIVE ANOMALIES CONTINUE TO REMAIN NEAR AVERAGE OVER THE EASTERN TROPICAL PACIFIC AND SLIGHTLY SUPPRESSED TO THE WEST OF THE DATE LINE FROM MAY 13 TO JUNE 7. ENHANCED CONVECTION WAS OBSERVED ACROSS INDONESIA DURING THIS TIME PERIOD. THE WIND ANOMALIES AT THE LOWER AND UPPER-LEVELS WERE NEAR AVERAGE DURING THE PAST MONTH. THESE ATMOSPHERIC INDICATORS ARE CONSISTENT WITH ENSO NEUTRAL CONDITIONS.

SEA SURFACE TEMPERATURES (SSTS) ARE SLIGHTLY ABOVE AVERAGE ACROSS THE EQUATORIAL PACIFIC. THE MOST RECENT THREE-MONTH MEAN TEMPERATURE ANOMALY FOR THE NINO 3.4 REGION IS +0.4 DEGREES CELSIUS. UPPER-OCEAN TEMPERATURES ARE FROM 0.5 TO 1 DEGREE C ABOVE AVERAGE TO DEPTHS OF ABOUT 100 TO 150 METERS ACROSS THE EQUATORIAL PACIFIC, HOWEVER, THE TOTAL HEAT CONTENT OF THE EQUATORIAL PACIFIC BETWEEN THE SURFACE AND 300 METERS DEPTH HAS DECREASED AFTER PEAKING IN EARLY MAY. NEGATIVE OUTGOING LONGWAVE RADIATION (OLR) ANOMALIES, INDICATING ENHANCED ATMOSPHERIC CONVECTION, WERE OBSERVED NEAR INDONESIA, WHILE POSITIVE ANOMALIES, INDICATING SUPPRESSED CONVECTION, WERE OBSERVED WEST OF THE DATE LINE. LOW-LEVEL WINDS AT 850-HPA AND UPPER-LEVEL WINDS AT 200-HPA HAVE BEEN NEAR LONG-TERM AVERAGES OVER THE EQUATORIAL PACIFIC. THESE ATMOSPHERIC AND OCEAN ANOMALIES INDICATE THE PERSISTENCE OF ENSO-NEUTRAL CONDITIONS.

DYNAMICAL MODELS SUCH AS THE CFS AND THE CONSENSUS OF NMME MODELS INDICATE A DECREASE IN THE LIKELIHOOD OF EL NINO CONDITIONS DEVELOPING IN THE NEXT FEW MONTHS RELATIVE TO FORECASTS MADE LAST MONTH. THE CPC CONSOLIDATION OF FORECASTS FROM THE CFS AND THREE STATISTICAL MODELS (CONSTRUCTED ANALOG, MARKOV AND CANONICAL CORRELATION ANALYSIS) FOR THE NINO 3.4 SST INDICATES LESS THAN A 50% PROBABILITY OF ANOMALIES GREATER THAN +0.5C THROUGH 2017 INTO THE BEGINNING OF 2018. THE CPC/IRI CONSENSUS ENSO FORECAST INDICATES SLIGHTLY GREATER THAN A 50% PROBABILITY OF CONTINUING ENSO NEUTRAL CONDITIONS INTO EARLY 2018. [Editor's Note: The latest CPC/IRI fully model-based forecast is a bit more optimistic about El Nino for late Fall and early Winter. The NOAA Seasonal Outlook is issued on June 15 but the updated CPC/IRI report is also issued on June 15 and we do not believe that the NOAA Seasonal Outlook reflects the June 15 version of the CPC/IRI Report. It takes time to produce this Seasonal Outlook and it can't possibly incorporate all of the most recent information] .THE MADDEN-JULIAN OSCILLATION, AS INDICATED BY THE RMM INDICES, WAS RECENTLY ACTIVE OVER THE WESTERN HEMISPHERE, HOWEVER, DYNAMICAL MODEL FORECASTS DO NOT PREDICT A COHERENT MJO SIGNAL AFTER THE NEXT COUPLE WEEKS. TROPICAL-EXTRATROPICAL TELECONNECTIONS DO NOT PLAY A ROLE IN THE CURRENT MONTHLY FORECAST.

PROGNOSTIC DISCUSSION OF SST FORECASTS

THE LATEST NCEP CFSV2 AND MOST OF THE MODELS OF THE NORTH AMERICAN MULTI-MODEL ENSEMBLE (NMME) ARE FAVORING A CONTINUATION OF ENSO-NEUTRAL CONDITIONS THROUGH THE FALL. THE CPC NINO 3.4 SST INDEX CONSOLIDATION FORECAST INDICATES A POSITIVE ANOMALY AT OR SLIGHTLY BELOW 0.5 DEGREES C THROUGH NDJ. DUE TO THESE LATEST MODEL PREDICTIONS ALONG WITH NEAR-AVERAGE ATMOSPHERIC CONDITIONS OVER THE PACIFIC, THE CPC/IRI CONSENSUS FORECAST INDICATES SLIGHTLY MORE CONFIDENCE (50 TO 55 PERCENT CHANCE) IN THE PERSISTENCE OF ENSO-NEUTRAL CONDITIONS THROUGH JFM 2018. THE CHANCES FOR EL NINO (AROUND 35 PERCENT) DURING THE UPCOMING FALL AND WINTER ARE SIMILAR TO THE CLIMATOLOGICAL PROBABILITY.

30-DAY OUTLOOK DISCUSSION FOR JULY 2017

WITHOUT THE INFLUENCE OF SIGNIFICANT CLIMATE MODELS OF VARIABILITY DURING THE NEXT MONTH, THE JULY TEMPERATURE AND PRECIPITATION OUTLOOKS ARE BASED PRIMARILY ON FORECASTS FROM THE NORTH AMERICAN MULTI-MODEL ENSEMBLE (NMME), WITH PARTICULAR FOCUS ON THE FORECASTS OF THE NCEP CLIMATE FORECAST SYSTEM (CFS), AND SOME ATTENTION TO AREAS WHERE THE INFLUENCE OF DECADAL TIMESCALE CLIMATE TRENDS IS GREATER.

Temperature

THE AVERAGE TEMPERATURE ANOMALY FORECAST FROM THE NMME FOR NORTH AMERICA INDICATES POSITIVE ANOMALIES OVER ALMOST THE ENTIRETY OF THE U.S. INCLUDING THE CONUS AND ALASKA. COUNTS OF ENSEMBLE MEMBERS FROM ALL OF THE MODELS INDICATES GREATER THAN 40% IN THE ABOVE NORMAL TERCILE IN ALMOST ALL OF THE U.S., EXCEPT NORTHERN ALASKA, THE NORTHWEST CONUS, AND A FEW SCATTERED SMALLER REGIONS IN THE EASTERN CONUS. PROBABILITY ANOMALY CORRELATION (PAC) CALIBRATED PROBABILITY FORECASTS INDICATE A COHERENT PATTERN OF LIKELY ABOVE NORMAL TEMPERATURES OVER MOST REGIONS, WITH REDUCED PROBABILITIES AND LOWER POTENTIAL SKILL OVER NORTHERN ALASKA, THE PACIFIC NORTHWEST, AND PARTS OF THE EASTERN CONUS CENTERED AROUND THE CENTRAL MISSISSIPPI VALLEY. RELYING ON THESE DYNAMICAL MODEL FORECASTS FROM THE NMME AND CFS, THE JULY TEMPERATURE OUTLOOK INDICATES INCREASED LIKELIHOOD OF ABOVE NORMAL TEMPERATURES FOR ALL REGIONS OF ALASKA AND THE CONUS EXCEPT FOR PARTS OF THE NORTHWEST, WHERE EQUAL CHANCES OF ABOVE, NEAR AND BELOW NORMAL TEMPERATURES IS INDICATED. PROBABILITIES EXCEED 50% OVER A LARGE AREA OF THE SOUTHWEST CONUS, WHERE DECADAL TRENDS HAVE A SIGNIFICANT INFLUENCE ON DYNAMICAL MODEL FORECASTS, AS WELL AS IN PARTS OF MAINE, TEXAS, FLORIDA AND ALASKA.

Precipitation

THE JULY PRECIPITATION OUTLOOK RELIES PRIMARILY ON PAC CALIBRATED PROBABILITY FORECASTS FROM THE NMME, AND TO SOME EXTENT, THE MOST RECENT RUNS OF THE CFS AT THE TIME OF THE FORECAST. CALIBRATED FORECASTS FROM THE NMME HAVE LARGE AREAS WHERE PROBABILITIES ARE NEAR EQUAL CHANCES FOR ABOVE, NEAR AND BELOW MEDIAN, INDICATING IN PART THE LOW SKILL OF MONTHLY PRECIPITATION FORECASTS INITIALIZED MORE THAN A HALF MONTH BEFORE JULY. LIMITED AREAS OF INCREASED PROBABILITIES IN THE JULY PRECIPITATION OUTLOOK ARE ALSO A RESULT OF WEAK PRECIPITATION TRENDS AND A LACK OF FORCED CLIMATE SIGNALS FOR MOST REGIONS. THE GREATEST SIGNALS FOR ABOVE MEDIAN PRECIPITATION ARE INDICATED TO BE IN THE WESTERN GULF COAST REGION, A SMALL AREA OF EASTERN MONTANA AND WESTERN NORTH DAKOTA, AND SOUTHWESTERN REGIONS OF ALASKA, INCLUDING THE ALEUTIAN ISLANDS. IN THESE AREAS, PROBABILITIES ARE GENERALLY WEAK AND ONLY EXCEED 40% IN SOME AREAS. A GREATER PROBABILITY OF BELOW MEDIAN PRECIPITATION IS INDICATED FOR PARTS OF THE GREAT BASIN AND CENTRAL ROCKIES. THOUGH THE SIGNAL FOR BELOW MEDIAN PRECIPITATION IN THE WEST IS WEAK IN THE NMME PROBABILITY FORECASTS, A LARGER AREA OF GREATER PROBABILITIES FOR BELOW MEDIAN IS SUPPORTED BY THE RECENT RUNS OF THE CFS.

July – August – September

Temperature

ABOVE-NORMAL TEMPERATURES ARE FAVORED ACROSS NEARLY ALL OF THE FORECAST DOMAIN FOR THE JAS OUTLOOK, AS THE TEMPERATURE TOOLS ARE IN GOOD AGREEMENT AND THE MOST RECENT NMME INCREASED COVERAGE OF ENHANCED ODDS FOR ABOVE-NORMAL TEMPERATURES. THE LOWEST PROBABILITIES FOR ABOVE-NORMAL TEMPERATURES ARE FORECAST ACROSS PARTS OF THE CENTRAL U.S. IN PART DUE TO INITIALLY HIGH SOIL MOISTURE ACROSS THE CENTRAL/SOUTHERN GREAT PLAINS AND UPPER MIDWEST, BUT THIS REDUCED AREA OF PROBABILITIES IS ALSO CONSISTENT WITH A CONSENSUS FROM THE VARIOUS TOOLS. EQUAL CHANCES OF BELOW-, NEAR-, OR ABOVE-NORMAL TEMPERATURES ARE LIMITED TO PARTS OF MONTANA BASED ON DYNAMICAL MODEL GUIDANCE AND THE CFS MODEL INDICATING A SMALL AREA OF BELOW-NORMAL TEMPERATURES.  PROBABILITIES FOR ABOVE-NORMAL TEMPERATURES DURING JAS ARE HIGHEST OVER THE NORTHEAST, PARTS OF THE GULF COAST AND FLORIDA, AND THE SOUTHWEST DUE TO DECADAL TRENDS AND CALIBRATED PROBABILITIES FROM THE NMME. THIS TOOL INDICATES INCREASED CHANCES FOR ABOVE-NORMAL TEMPERATURES ACROSS MUCH OF ALASKA WITH THE HIGHEST CHANCES (50 AND ABOVE) OVER SOUTHWEST ALASKA AND THE ALEUTIANS.

Precipitation

ENHANCED ODDS FOR ABOVE-MEDIAN PRECIPITATION DURING JAS ARE MAINTAINED FROM ONE MONTH AGO ACROSS THE NORTH-CENTRAL U.S. AND PARTS OF ALASKA, BASED ON THE MOST RECENT DYNAMICAL MODEL GUIDANCE. PRECIPITATION TOOLS FEATURE A WET SIGNAL ACROSS THE WESTERN GULF COAST REGION AND INCREASED CHANCES FOR ABOVE-MEDIAN PRECIPITATION DURING JAS IS INTRODUCED TO THIS REGION. THE SIGNAL IS GENERALLY WEAK AMONG PRECIPITATION TOOLS WITH MONSOON RAINFALL ACROSS THE SOUTHWEST DURING JAS 2017. THEREFORE, EQUAL CHANCES OF BELOW-, NEAR-, OR ABOVE-MEDIAN PRECIPITATION ARE FORECAST FOR THE SOUTHWEST DURING JAS.  

PROGNOSTIC DISCUSSION OF OUTLOOKS - JAS 2017 TO JAS 2018 with emphasis on months beyond September 2017

DURING THE FALL AND WINTER 2017-18, CHANCES OF EL NINO DEVELOPMENT HAVE DECREASED COMPARED TO THE PREVIOUS MONTH. SINCE ENSO-NEUTRAL CONDITIONS ARE MOST LIKELY TO PERSIST, THE TEMPERATURE AND PRECIPITATION OUTLOOKS DURING THE COLD SEASON ARE BASED PRIMARILY ON DYNAMICAL MODEL GUIDANCE AND DECADAL TRENDS. EQUAL CHANCES (EC) ARE FORECAST OVER AREAS WHERE ODDS OF ABOVE-, BELOW-, OR NEAR-NORMAL SEASONAL MEAN TEMPERATURES AND SEASONAL ACCUMULATED PRECIPITATION AMOUNTS ARE EXPECTED TO BE SIMILAR TO CLIMATOLOGICAL PROBABILITIES.  

TEMPERATURE

THE TEMPERATURE OUTLOOKS FROM ASO 2017 TO NDJ 2017-18 ARE BASED PRIMARILY ON THE NMME CALIBRATED PROBABILITIES SINCE THE MOST LIKELY OUTCOME IS FOR ENSO-NEUTRAL CONDITIONS DURING THESE SEASONAL PERIODS. AN EXPECTED LACK OF SEA ICE ELEVATES CHANCES FOR ABOVE-NORMAL TEMPERATURES ACROSS NORTHERN ALASKA DURING THE FALL SEASON. DECADAL TRENDS ARE USED IN CREATING THE TEMPERATURE OUTLOOKS AT THE LONGER LEAD TIMES DURING THE SPRING AND SUMMER OF 2018.

PRECIPITATION

SINCE THE PREVIOUS OUTLOOK, THE CHANCES FOR EL NINO DEVELOPMENT DURING THE NEXT SIX MONTHS HAVE DECREASED. GIVEN THE LATEST CPC/IRI CONSENSUS FORECAST FAVORING A CONTINUATION OF ENSO-NEUTRAL CONDITIONS THROUGH THE WINTER 2017-18, IT WAS NECESSARY TO REMOVE THE INCREASED CHANCES FOR ABOVE-MEDIAN PRECIPITATION OVER THE GULF COAST REGION AND SOUTHEAST DURING THE UPCOMING FALL AND WINTER.

PRECIPITATION OUTLOOKS (THROUGH NDJ 2017-18) ARE BASED PRIMARILY ON GUIDANCE FROM THE CALIBRATED PROBABILITIES FROM THE NMME WHICH DEPICTS INCREASED CHANCES FOR ABOVE-MEDIAN PRECIPITATION FROM THE FOUR CORNERS REGION EXTENDING INTO THE NORTH-CENTRAL U.S.  PRECIPITATION OUTLOOKS AT LATER LEADS ARE BASED ON THE CONSOLIDATION AND DECADAL TRENDS.

Forecasting the Evolution of ENSO

Here is the JAMSTEC new Nino 3.4 forecast.

June 1, 2017 Nino 3.4 Forecast.

Notice that this new forecast peaks briefly at about 0.7C and seems to be at 0.5C or above from November 2017 through February 2018. Obviously no one expects a forecast to work out exactly as forecast but, as forecast, this event most likely will not meet the U.S. standard for an El Nino which with respect to the Nino 3.4 Index component would require five consecutive three-month periods where the Nino 3.4 average equaled or exceeded 0.5C. We do not have the discussion yet from JAMSTEC. That should follow soon and probably will be available for our report on the seasonal outlooks of the two agencies which we plan to publish Saturday evening.
Are they hinting at a La Nina for the following winter? That is a long way off.

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.

 CFS.V2 SST Forecast June 12, 2017

It is not showing an El Nino for Fall and Winter. In fact the temperature anomaly declines after this summer.
Thus both the NOAA and JAMSTEC forecasts are signaling ENSO Neutral but the peak level of the Nino 3.4 Index occurs six months later in the JAMSTEC forecast which would impact monthly temperature and precipitation forecasts.
But there is a big spread among the various forecast members for both the NOAA and JAMSTEC Nino 3.4 forecasting tools. So there is not a high level of confidence in these forecasts. I am using this NOAA image rather than 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. 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.

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 June 15, 2017 fully model-based report on the right and the earlier June 8 less formal mostly based on a Meteorologist survey on the left.

June 15, 2017 IRI/CPC ENSO Side by Side Forecasts.

It is very interesting that the new CPC/IRI probability analysis is somewhat more consistent with that of JAMSTEC. It was issued today just as the NOAA Update was issued today but clearly the NOAA update did not take the new report from the CPC/IRI into account. If they had, their maps would probably be somewhat closer to those of JAMSTEC but we have not gotten to that part of the analysis yet. It takes NOAA some number of days to prepare and issue their seasonal outlook so it does not take into account the most recent information. But we are able to fill in that gap to some extent.

IRI Technical ENSO Update

Published: June 15, 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-June 2017, the NINO3.4 SST anomaly hovered close to the borderline of a weak El Niño level. For May the SST anomaly was 0.46 C, near the borderline of weak El Niño, and for Mar-May it was 0.30 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 0.4, approaching the borderline of weak El Niño. The pertinent atmospheric variables, including the upper and lower level zonal wind anomalies, have been showing neutral patterns. The Southern Oscillation Index (SOI) had been somewhat below average, indicating an El Niño tendency, but recently has returned to near-average. Subsurface temperature anomalies across the eastern equatorial Pacific have been just slightly above average. Overall, given the SST and the atmospheric conditions, an ENSO-neutral diagnosis remains appropriate.

Expected Conditions

What is the outlook for the ENSO status going forward? The most recent official diagnosis and outlook was issued one week ago in the NOAA/Climate Prediction Center ENSO Diagnostic Discussion, produced jointly by CPC and IRI; it stated that ENSO-neutral has an approximately 50 to 55% chance of persisting during northern summer and fall, with slightly lower chances for El Niño development. The latest set of model ENSO predictions, from mid-June, 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 ENSO-neutral or the weak El Niño range for June-Aug and show a slowly increasing likelihood (but still below 50%) for El Niño development in fall and early winter.

As of mid-June, 72% of the dynamical or statistical models predicts neutral ENSO conditions for the initial Jun-Aug 2017 season, while 28% predicts El Niño conditions and 0% predicts La Niña 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 Sep-Nov 2017 season, among models that do use subsurface temperature information, no model predicts La Niña conditions, 24% predicts El Niño conditions, while 76% predicts neutral ENSO. For all model types, the probabilities for La Niña are less than 10% for for all predicted seasons from Jun-Aug 2017 through Feb-Apr 2018. The probability for El Niño conditions is less than 40% throughout the series of forecast periods ending Feb-Apr 2008, and rise to 35-40% between Nov-Jan and Feb-Apr. Chances for neutral ENSO conditions are mainly between 70 and 80% through Oct-Dec 2017, and then steadily drop to near 55% by the final season of Feb-Apr 2018.

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 at 15% or less from Jun-Aug 2017 through the final season of Feb-Apr 2018, with highest probabilities near 15% during Oct-Dec and Nov-Jan. Probabilities for ENSO-neutral are at least 60% for Jun-Aug and Jul-Sep, dropping below 50% from Sep-Nov to Dec-Feb and rising to near 60% by the final season of Feb-Apr 2018.  Probabilities for El Niño are 30 to 40% from Jun-Aug to Aug-Oct, rising to 40-45% for Sep-Nov to Jan-Mar and dropping to 35% for Feb-Apr 2018.  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 ENSO-neutral throughout the forecast period, with chances for El Niño peaking at 40-45% during fall and winter. Chances for La Niña are relatively low throughout the forecast period.  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 by CPC and IRI, which will include some human judgment in combination with the model guidance. [Editor's Note: This is either artifact or where it says June they mean July]

A look at the subsurface is very useful.

Subsurface Conditions date June 12, 2017

I have "frozen" this chart (which updates every five days) at June 12, 2017 which is the midpoint of the five-day period covered. One can see warm water in place both on the surface and below extending out from the Coast of Ecuador to 150W. But it is a fairly shallow reservoir of warm water with cool water not very far below it. More importantly the water to the west is not particular warm. There is a warm anomaly at about 150E but it is not going to keep the surface of the Nino 3.4 Measurement Area which extends from 170W to 120W and also 5 degrees north and south of the Equator above 0.5C as measured on an anomaly basis for the length of time needed to establish an El Nino. It is a situation that is right now within the Neutral Range but with a warm bias.
It could well be that the every five years adjustment mechanism NOAA uses for the Tropical Pacific is not able to keep up with Ocean Warming which may slightly overstate warm anomalies.

SOI values as of June 17, 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 remain in the ENSO Neutral phase of ENSO. They do have a warm bias to them. You can also see that month to month there has been a  lot of fluctuation and that is thought to also impact weather perhaps as much as the absolute value of SOI.

Here is the most recent Nino 3.4 report from the Australian BOM.

Australia POAMA ENSO model run June 4, 2017

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 through their forecast period. This report will be updated in a few days but we can only work from what has been published and is available. If it changes dramatically on Monday Night I may update this graphic.

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

JAMSTEC works in three-month intervals and does not change the selection of months each time they update. So we have  JJA, SON, and DJF to work with from JAMSTEC and JAS, SON, and DJF to work with from NOAA. So this month things do not line up perfectly for the first three-month period which for NOAA is JAS. In two updates out of three they do not line up perfectly in the first three-month period and this is one of the two times where it is not exactly the same three months. That should not make much difference as we will compare NOAA's JAS to JAMSTEC'S' JJA and there are two months that are the same and one that is one month earlier or later. It is something to keep in mind but it does not invalidate the approach. The two further out periods will line up correctly. .

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 and enlarge the Europe Section of the Worldwide JAMSTEC maps.

JJA/JAS

Temperature

NOAA (JAS)

JJA 2017 Temperature Issued by NOAA on June 15, 2017

And here is the JJA temperature forecast for North America that I extracted from the JAMSTEC World Forecast

JJA JAMSTEC extracted from June 1, 2017 World Forecast

NOAA shows a North Central area that is EC. For JAMSTEC, everything is warm.

And Now the JAMSTEC WORLD FORECAST

JJA Temperature Forecast from JAMSTEC June 1, 2017 forecast.

For the World, JAMSTEC sees very little that is cool other than North Central Siberia and Eastern Brazil. Other cool areas are a small part of West Africa and part of Western Canada and to some extent the Maritime Continent.

Precipitation

NOAA JAS

NOAA JJA 2017 Precipitation Issued June 15, 2017

And here is the JJA Temperature Forecast for North America that I extracted from the JAMSTEC World Forecast; Remember from JAMSTEC it is a JJA forecast not JAS as is the case with NOAA.

CONUS JJA Precipitation Extracted from June 1, JAMSTEC Forecast

For CONUS, NOAA shows a small part of Alaska wet and two CONUS wet anomalies, the most interesting being associated with the Western Gulf of Mexico. JAMSTEC is showing Alaska fairly wet. For CONUS, JAMSTEC shows perhaps the same GOM wet anomaly shifted a bit further west which is one variation showing up in the NOAA models also but JAMSTEC is showing a wet Northeast and a lot of dry area. JAMSTEC also shows New Mexico dry, which is bolder than NOAA which simply says their Monsoon signal is weak.

JAMSTEC WORLD FORECAST

JJA 2017 Jamstec Precipitation Forecast From June 1, 2017

Of interest is the dry South America, Australia, and wet West Africa and Central America.

SON 2017

Temperature

NOAA

SON Temperature NOAA Issued on June 1, 2017

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

SON North American Temperature extracted from JAMSTEC June 1 Forecast

NOAA and JAMSTEC agree pretty much here but JAMSTEC hints at a cooler area in the Southeast.

JAMSTEC WORLD FORECAST

SON 2017 JAMSTEC Temp from June 1, 2017

For JAMSTEC it is difficult to find cool anomalies for SON. The most notable one is the UK and part of France. The Maritime Continent is somewhat cool as is Somalia. Central China is cool and part of Argentina is cool.

Precipitation

NOAA

NOAA SON 2017 Precipitation Issued on June 1, 2017

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

SON JAMSTEC Precipitation for CONUS based on June 1 forecast

NOAA and JAMSTEC differ a bit on which part of Alaska will be wet. NOAA is showing a Rocky Mountains wet pattern that widens towards the north. JAMSTEC shows more of a dry to EC 2/3rds of CONUS to the west and 1/3rd of CONUS wet to the east.

JAMSTEC WORLD FORECAST

SON 2017 JAMSTEC Precipitation Forecast from June 1, 2017

Northern Europe is wet. Australia and more intensely the island nations north of Australia are dry. Only a small part of India is dry. Eastern Asia is dry. Equatorial and much of southern Africa is wet. Most of Western South America is wet but Eastern South America is dry.

DJF 2017-2018

Temperature

NOAA

NOAA DJF 2017- 2018 Temperature Issued June 15, 2017

And here is the DJF 2017-2018 Temperature Forecast for North America that I extracted from the JAMSTEC World Forecast

DJF 2017-2018 North America Temperature Forcast Extracted from the June 1 JAMSTEC Forecast

NOAA has both Alaska and CONUS warm except for the North Central area which is EC. For JAMSTEC, only the Southwestern third of CONUS plus Southern Florida is warm. The rest extending into Canada is cool.

JAMSTEC WORLD FORECAST

DJF 2017 - 2018 JAMSTEC Temperature from June 1, 2017

One major cool area is CONUS. Another is Europe excluding Scandinavia. But there are other cool areas such as parts of Central Asia and Southwest China.

Precipitation

NOAA

DJF 2017 Precipitation Issued June 1, 2017

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

JAMSTEC DJF precipitation extracted from their June 1 2017 Forecast

CONUS does not have much to say about DJF 2017-2018 CONUS precipitation. The JAMSTEC forecast is especially adamant about a wet California and wet Northeast. Texas is dry.

JAMSTEC WORLD FORECAST

JAMSTEC DJF2018. Precipitation from 1jun2017

South Africa is wet, Australia is no longer dry. Much of South America is wet especially Eastern Brazil. Much of Asia is wet. Northern Europe is dry.

Conclusion

Both forecasts are based on either no El Nino or some short period of El Nino Conditions which does qualify as an El Nino. The timing of the rise and fall of the Nino 3.4 Index varies between NOAA and JAMSTEC which I believe explains why the JAMSTEC third period has more El Nino characteristics than NOAA's third period and why the first two periods are are shown for precipitation significantly different by NOAA and JAMSTEC.

End Note

A final comment about temperature. One normally sees more temperature anomalies in these maps than precipitation anomalies. The adjustment mechanism for trends in most cases involves adjusting the norm or "climatology" every decade to calculate a three-decade average and in the special case of the Equatorial Pacific for purposes of assessing in retrospect the ENSO anomalies, the adjustment is made very five years. When there is a rising trend, the average tends to be lower than the current values so one tends to see more warm anomalies than cool anomalies. That same problem does not exist with precipitation or if it does, it may exist in the opposite direction but at a much lower magnitude as the Planet may be getting wetter as it gets warmer. So far no one has come up with a good solution for dealing with trends some of which may be long cycles and some may be secular trends. It is worth being aware of especially when we have fixed criteria for how to interpret anomalies. 

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

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