NOAA Issues Seasonal Update – Extent of Disagreement Surprising

Written by Sig Silber

NOAA issued their Seasonal Outlook on March 16 and JAMSTEC pretty much followed the same schedule. The forecasts are surprisingly different given that both agencies are forecasting an El Nino but JAMSTEC with more confidence. Here at GEI we think both Meteorological Agencies are incorrect on that forecast but we’ll go over what they are presenting.

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 only out to Sept – Nov 2017) is reflecting a higher probability of El Nino conditions next Fall.

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 March is discussed [click here ] This  makes all forecasts right now beyond the next three months somewhat of a WAG. We are also watching a possible Climate Shift in the Pacific to a period lasting two to three decades of PDO Positive.

Some Housekeeping Issues

This report will be posted late Saturday March 18 and will be referred to in the Weekly Report for reference until the Saturday after the next NOAA Update on April 20, 2017 which we will report on April 22. The Regular Weekly Report will be published on March 20. 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 precipitation forecasts for three time periods first NOAA then JAMSTEC also for the U.S. and then JAMSTEC for Europe. 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 Spring, Summer and into Fall.

	NOAA US	JAMSTEC US	JAMSTEC Europe
AMJ for NOAA MAM for JAMSTEC
JJA
SON

NOAA Updated Seasonal Outlook

NOAA issued their updated Seasonal Outlook on the third Thursday of the month i.e. March 16, 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 April 2017. It is called the Early Outlook because it will be updated at the end of March. Only the April 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 April maps from the February 16, NOAA Report to compare against. And March is not over so we can not really compare the April forecast against March actual. It is probably best to just try to understand what NOAA is trying to convey about April which can be summarized as for temperature we have a shifting to the East of the warm anomaly and for precipitation we have the end of the stream of Pacific moisture entering CONUS but two wet anomalies one in the North Central area and another along the Western Gulf of Mexico coast.

Now we consider the three-month Outlook.

Notice that the three-month periods are abbreviated e.g. April/May/June is shown as AMJ. You will see such abbreviations often in this report.

Prior Temperature Outlook for AMJ 2017

New Temperature Outlook for AMJ 2017

There is essentially no change in the three-month forecast with respect to the spacial aspects of the anomalies other than the prior Alaska EC area is now shown as warm. But with respect to the CONUS warm anomaly, the higher probabilites have shifted to the East.

Prior Precipitation Outlook for AMJ 2017

New Precipitation Outlook for AMJ 2017

Now let us focus on the long-term situation and compare the new set of maps with the maps issued on February 16, 2016.

Prior 14 Month Temperature Outlook: AMJ  2017 – MAM 2018

New 14 Month Temperature Outlook: MJJ 2017 – AMJ 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: AMJ 2017 – MAM 2018

New 14 Month Precipitation Outlook: MJJ 2017 – AMJ 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           

One can mentally subtract the April Outlook from the three-month Outlook and create the Outlook for the last two months in the three-month period namely May and June 2017. If you look carefully you will see four levels of probability of being different than EC: 33%, 40%, 50% and 60%. I am not sure if NOAA calls those levels “classes” as they may just refer to +, – and EC as classes i.e. three levels. But they show nine levels of probabilities on these maps: EC plus four levels of positive deviation from normal and four in the other direction. You can use this information to quantify the differences between the one month and three month maps. When you do that you see that:

Discussion

Below are excerpts (significantly reorganized and with some of the redundancy removed) from the Discussion released by NOAA on March 16, 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 THAT ENSO-NEUTRAL CONDITIONS ARE NOW IN PLACE. A RESIDUAL, GENERALLY SMALL, AREA OF BELOW NORMAL SEA SURFACE TEMPERATURES (SSTS) PERSISTS IN PROXIMITY TO THE DATE LINE, BUT IN MOST AREAS ALONG THE EQUATOR, OCEAN SURFACE TEMPERATURES ARE NOW ABOVE AVERAGE, ESPECIALLY FOR THE EASTERN AREAS OF THE BASIN WHERE THE LATEST WEEKLY VALUE OF THE NINO1+2 INDEX WAS +2.1 DEGREES C.

AT DEPTH, THE UPPER-OCEAN (TOP 300 METERS) HEAT CONTENT ANOMALY SUMMED ACROSS THE BASIN FROM THE DATE LINE TO 100W BECAME POSITIVE DURING JANUARY AND CONTINUED TO INCREASE DURING FEBRUARY INTO EARLY MARCH. IT NOW REFLECTS A VALUE OF +0.4 DEGREES C INDICATING CONSIDERABLE AREAS OF ABOVE-AVERAGE OCEAN TEMPERATURES BELOW THE SURFACE.

IN THE ATMOSPHERE OVER THE PAST MONTH, EASTERLY WIND ANOMALIES CONTINUED TO BE OBSERVED OVER THE WESTERN TROPICAL PACIFIC. OVER THE SAME PERIOD, ANOMALOUS TROPICAL CONVECTION INDICATED CONTINUED SUPPRESSED CONVECTION IN THE CENTRAL PACIFIC BUT CONTINUING ENHANCED CONVECTION IN THE FAR WESTERN PACIFIC PRIMARILY NORTH OF THE EQUATOR. THE REMAINING DIPOLE IN ANOMALOUS CONVECTION INDICATES SOME SIGNATURES OF THE PAST WEAK LA NINA EVENT HAVE BEEN SLOW TO FADE.  

PROGNOSTIC DISCUSSION OF SST FORECASTS

THE CPC SST CONSOLIDATION FORECAST, WHICH INCLUDES THREE STATISTICAL FORECASTS ALONG WITH THE CFS, PREDICTS ENSO-NEUTRAL CONDITIONS WILL PERSIST FROM NOW UNTIL THE UPCOMING WINTER SEASON. THERE IS A CONSIDERABLE DIFFERENCE, HOWEVER, BETWEEN THE CFS AND THE STATISTICAL GUIDANCE AS THE CFS FAVORS AN INCREASE IN SST QUITE EARLY IN THE OUTLOOK PERIOD ENTERING EL NINO CONDITIONS DURING THE AMJ 2017 SEASON WHILE THE AFOREMENTIONED STATISTICAL TOOLS FAVOR ENSO-NEUTRAL CONDITIONS.  THIS SEPARATION BETWEEN THE STATISTICAL AND DYNAMICAL MODELS IS ALSO DEPICTED BY THE LATEST IRI NINO3.4 SST FORECAST PLUME. MOREOVER, FORECASTS FROM THE DYNAMICAL SUITE OF MODELS FROM THE NMME ALSO INDICATES A MORE ROBUST AND EARLIER INCREASE IN NINO3.4 SST DURING THE SPRING AND SUMMER MONTHS. THE LATEST OFFICIAL ENSO OUTLOOK FROM CPC/IRI FAVORS ENSO-NEUTRAL CONDITIONS TO CONTINUE THROUGH AT LEAST THE NORTHERN HEMISPHERE SPRING WITH INCREASING ODDS FOR THE DEVELOPMENT OF EL NINO CONDITIONS AS AUTUMN APPROACHES WITH PROBABILITIES FOR EL NINO REACHING NEAR 50% BY JAS 2017 AND APPROXIMATELY REMAINING AT THESE ODDS THROUGH OND 2017. AT THE CURRENT TIME, THE PROSPECTS FOR A ENSO COLD EVENT ARE SMALL (UNDER 10%) FOR MUCH OF THE OUTLOOK PERIOD.

30-DAY OUTLOOK DISCUSSION FOR APRIL 2017  

OCEANIC AND MOST ATMOSPHERIC SIGNALS ASSOCIATED WITH LA NINA CONDITIONS HAVE DIMINISHED, AND ENSO NEUTRAL CONDITIONS HAVE BEEN IN PLACE SINCE LAST MONTH. ONE REMNANT OF PRIOR LA NINA CONDITIONS OBSERVED DURING THE MONTH OF MARCH WAS ANOMALOUSLY ABOVE NORMAL OUTGOING LONGWAVE RADIATION NEAR THE DATE LINE INDICATING SUPPRESSED CONVECTION AND ANOMALOUSLY BELOW NORMAL OUTGOING LONGWAVE  RADIATION OVER THE NORTHERN MARITIME CONTINENT AND FAR WESTERN PACIFIC, WHERE CONVECTION WAS ENHANCED. THIS PATTERN MAY HAVE BEEN SOMEWHAT DUE TO AN ACTIVE  SUBSEASONAL MADDEN JULIAN OSCILLATION (MJO). CURRENTLY, THE MJO IS INACTIVE, AS INDICATED BY THE WHEELER AND HENDON RMM INDEX. IN CONSIDERATION OF THE CURRENT MJO AND ENSO INDICES, MJO AND ENSO DO NOT HAVE AN IMPACT ON THE APRIL CLIMATE OUTLOOK.

ANOMALOUSLY ABOVE NORMAL SNOW PACK AND SOIL MOISTURE OVER THE WESTERN CONUS, AND BELOW NORMAL SOIL MOISTURE OVER MUCH OF THE EASTERN CONUS, AS WELL AS ABOVE NORMAL SEA SURFACE TEMPERATURES NEAR THE GULF COAST, WERE CONSIDERED IN THE APRIL CLIMATE OUTLOOK. HOWEVER, THE HALF-MONTH LEAD APRIL 2017 OUTLOOK RELIES PRIMARILY ON MONTHLY FORECASTS FROM DYNAMICAL MODELS, INCLUDING THE CFS AND THE NMME, ALSO CONSIDERING WEEK 3-4 FORECASTS FROM THE CFS AND ECMWF ENSEMBLE PREDICTION SYSTEMS.

THE APRIL 2017 TEMPERATURE OUTLOOK INDICATES ENHANCED PROBABILITIES OF ABOVE NORMAL TEMPERATURES FOR MUCH OF THE CONUS, AS WELL AS ALASKA. DECADAL TIMESCALE TEMPERATURE TRENDS PLAY A SIGNIFICANT ROLE IN INCREASING THE PROBABILITIES OF ABOVE NORMAL TEMPERATURES FROM THE SOUTHWEST, ACROSS THE SOUTHERN CONUS, AND FOR MUCH OF THE EASTERN CONUS, AS WELL AS ALASKA. NMME PROBABILITIES, CALIBRATED USING MULTI-DECADAL HINDCASTS, INDICATE THE GREATEST PROBABILITIES FOR ABOVE NORMAL TEMPERATURES TO BE ALONG THE GULF COAST FOR APRIL. THE PROBABILITIES OF ABOVE NORMAL TEMPERATURES ARE ENHANCED IN THIS REGION BY OBSERVED AND PREDICTED ABOVE NORMAL SEA SURFACE TEMPERATURES FOR THE GULF OF MEXICO. CALIBRATED NMME PROBABILITIES FOR ABOVE NORMAL TEMPERATURES ARE WEAKLY ENHANCED OVER THE SOUTHWEST. BELOW NORMAL SOIL MOISTURE IN MUCH OF THE EASTERN CONUS MAY PLAY A ROLE IN INCREASING THE CHANCES THAT ABOVE NORMAL TEMPERATURES WILL PERSIST FOR APRIL MEAN TEMPERATURES. ABOVE NORMAL SNOW PACK IN THE WEST, AS WELL AS A PREDICTED TROUGH OVER THE WEST IN CFS AND ECMWF WEEK 3-4 FORECASTS, ALSO INDICATE LOWER PROBABILITIES OF ABOVE NORMAL TEMPERATURES OVER MUCH OF THE WEST. FOR THE FOUR CORNERS REGION, WHERE DECADAL TEMPERATURE TRENDS ARE A GREATER FRACTION OF INTERANNUAL TEMPERATURE VARIABILITY, A SMALL ENHANCEMENT OF ABOVE NORMAL TEMPERATURE PROBABILITIES IS INDICATED.  

THE APRIL 2017 PRECIPITATION OUTLOOK IS BASED PRIMARILY ON THE PRECIPITATION FORECASTS FROM THE CFS AND NMME. CALIBRATED PROBABILITIES OF ABOVE MEDIAN PRECIPITATION ARE GREATEST ALONG THE WESTERN GULF COAST FROM TEXAS TO THE FLORIDA PANHANDLE, AS INDICATED BY THE NMME, WITH PREDICTED SOUTHERLY FLOW FROM THE GULF OF MEXICO. RECENT INITIALIZATIONS OF THE CFS PREDICT A PERSISTENT POSITIVE MID-LEVEL HEIGHT ANOMALY OVER THE NORTH PACIFIC FOR APRIL. DOWNSTREAM  OF THIS POSITIVE ANOMALY, A RELATIVE TROUGH IS PREDICTED OVER THE WESTERN CONUS, AND A POSITIVE HEIGHT ANOMALY IS PREDICTED OVER THE EASTERN CONUS INTO THE NORTH ATLANTIC. THIS CIRCULATION FORECAST IS ALSO SUPPORTED BY WEEK 3-4 FORECASTS FROM BOTH THE CFS AND ECMWF ENSEMBLES. THE PROBABILITIES OF BELOW MEDIAN PRECIPITATION ARE ENHANCED SLIGHTLY FOR COASTAL REGIONS OF THE PACIFIC NORTHWEST, TO THE WEST OF THE PREDICTED TROUGH, WHILE PROBABILITIES OF ABOVE MEDIAN PRECIPITATION ARE SLIGHTLY INCREASED OVER THE NORTHERN AND CENTRAL PLAINS, AHEAD OF THE PREDICTED TROUGH. PROBABILITIES OF BELOW MEDIAN PRECIPITATION ARE ALSO SLIGHTLY ENHANCED FOR THE ALEUTIAN ISLANDS, AS INDICATED BY THE NMME CONSENSUS FORECAST.

Three Months April – May – June

Temperature

THE LATEST AMJ 2017 TEMPERATURE OUTLOOK INDICATES GENERALLY MINOR CHANGES FROM THE PREVIOUS OUTLOOK. AS SHOWN, ABOVE-NORMAL TEMPERATURES ARE FAVORED FOR MUCH OF THE FORECAST DOMAIN. FOR THE CONTIGUOUS U.S., THERE IS AN ENHANCED LIKELIHOOD OF ABOVE-NORMAL SEASONAL MEAN TEMPERATURES FOR A REGION STRETCHING FROM THE SOUTHWEST, EASTWARD TO INCLUDE MUCH OF THE CENTRAL AND EASTERN U.S. THE GREATEST ODDS (EXCEEDING 50% PROBABILITY) ARE LOCATED ACROSS THE SOUTH-CENTRAL PLAINS AND EASTERN CONUS. SHORT TERM CLIMATE PREDICTION MODELS (CFS, ECMWF, NMME SUITE AND IMME SUITE) OVERWHELMINGLY SUPPORTED THE CONTINUATION OF THIS SOLUTION INTO AND THROUGH THE SPRING WITH THE CALIBRATED PROBABILISTIC GUIDANCE FROM THE NMME INDICATING 50% OR GREATER ODDS FOR RELATIVE WARMTH IN THE AREAS HIGHLIGHTED WITH THE LARGEST OUTLOOK PROBABILITIES. NEGATIVE SOIL MOISTURE DEPARTURES IN SOME AREAS OF THIS DESIGNATED REGION ALSO CONTRIBUTED TO THE FAVORED ANOMALOUS WARMTH. SOME STATISTICAL FORECAST TOOLS AND LONG TERM TRENDS FURTHER SUPPORTED THE OUTLOOK.

POSITIVE SOIL MOISTURE DEPARTURES AND ELEVATED SNOWPACK IN SOME AREAS ACROSS THE NORTHERN TIER OF THE U.S. FROM THE NORTHERN HIGH PLAINS WESTWARD TO INCLUDE MUCH OF THE WEST, ALONG WITH WEAK SHORT TERM CLIMATE PREDICTION MODEL SIGNALS IN THESE AREAS RESULTED IN A DESIGNATION OF EQUAL CHANCES (EC) OR A REDUCTION IN PROBABILITIES FOR ABOVE-NORMAL TEMPERATURES FROM THE PREVIOUS OUTLOOK IN THESE REGIONS.

ABOVE-NORMAL TEMPERATURES ARE ALSO FAVORED FOR MUCH OF ALASKA.  

Precipitation

FOR PRECIPITATION, THE AMJ 2017 OUTLOOK FAVORS ABOVE-MEDIAN PRECIPITATION FOR A REGION ACROSS THE NORTHERN ROCKIES AND NORTHERN HIGH PLAINS AS WELL AS ALONG THE WESTERN GULF COAST. BELOW-MEDIAN PRECIPITATION IS MOST LIKELY FOR AREAS OF WESTERN ALASKA INCLUDING THE ALEUTIANS. THE OUTLOOK IS PRIMARILY BASED ON AVAILABLE DYNAMICAL MODEL GUIDANCE AND LONG TERM TRENDS IN LOCATIONS WHERE THEY ARE DEEMED SOMEWHAT RELIABLE (I.E., NORTHERN ROCKIES, NORTHERN PLAINS).

PROGNOSTIC DISCUSSION OF OUTLOOKS – AMJ 2017 TO AMJ 2018 (AMJ covered separately above)

TEMPERATURE

MANY OF THE REMAINING TEMPERATURE OUTLOOK MAPS SAW LITTLE CHANGE FROM THE PREVIOUS SET OF OUTLOOKS AS STATISTICAL AND DYNAMICAL FORECAST TOOL INDICATORS DID NOT VARY STRONGLY. SOME EXCEPTIONS INCLUDE THE FOLLOWING. SLIGHTLY LOWER PROBABILITIES FOR ABOVE-NORMAL TEMPERATURES ARE NOW INDICATED FOR AREAS OF THE WEST DURING MJJ 2017 DUE TO PREVIOUSLY MENTIONED INITIAL LAND SURFACE CONDITIONS. WARMER GUIDANCE SUPPORTED AN INCREASE IN PROBABILITIES FOR ABOVE NORMAL TEMPERATURES FOR THE EASTERN U.S. DURING JJA, JAS AND ASO 2017. LOW PROBABILITIES FOR LA NINA CONDITIONS AND CONSEQUENTLY ELEVATED ODDS FOR EL NINO CONDITIONS POTENTIALLY ENTERING THE AUTUMN FAVORED A SLIGHT INCREASE IN PROBABILITIES FOR ABOVE-NORMAL TEMPERATURES ALONG THE NORTHERN TIER IN THE CENTRAL AND EASTERN CONUS FOR SON, OND 2017 AND NDJ 2017-2018.

FOR ALASKA, HIGH PROBABILITIES FOR ABOVE-NORMAL TEMPERATURES ARE INDICATED FOR THE NORTH SLOPE DUE TO RECENT TRENDS IN SEA ICE COVERAGE AND TIMING DURING SON AND OND 2017.

PRECIPITATION

HIGHLIGHTED AREAS FOR THE MJJ THROUGH ASO 2017 SEASONS ARE IN AREAS WHERE THERE WAS CONSISTENT, ALBEIT OFTEN WEAK, SIGNATURES INDICATED BY CALIBRATED PROBABILISTIC GUIDANCE FROM THE NMME SUITE OF MODELS. THIS INCLUDES A CONTINUATION OF ELEVATED ODDS FOR ABOVE-MEDIAN PRECIPITATION FOR AREAS IN THE NORTHERN ROCKIES AND NORTHERN HIGH PLAINS. BY ASO 2017, CONSIDERATIONS AS NOTED ABOVE REGARDING INCREASING ODDS FOR EL NINO ALLOW A SLIGHT SOUTHWARD SHIFT OF THIS REGION. BELOW-MEDIAN PRECIPITATION CONTINUES FOR PARTS OF WESTERN ALASKA  IN MJJ 2017 AND IS INTRODUCED IN MJJ AND JJA 2017 NEAR THE OHIO VALLEY. THERE IS A SLIGHT TILT IN THE ODDS FOR ABOVE MEDIAN PRECIPITATION FOR PORTIONS OF EASTERN MAINLAND ALASKA FROM MJJ TO JAS 2017.

FOR LATER LEADS, THE LOW PROBABILITIES FOR LA NINA AT THE CURRENT TIME AND CONSEQUENTLY ELEVATED ODDS FOR POTENTIAL EL NINO CONDITIONS RESULTED IN REMOVAL OF SOME DRY SIGNALS IN PREVIOUS OUTLOOKS ACROSS THE SOUTHERN TIER OF THE U.S., IN PARTICULAR THE SOUTHEAST CONUS BEGINNING IN NDJ 2017-2018.

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 anomalies measured by the Nino 3.4 Index. It confirms rather than predicts the phases of ENSO. We will present the SOI data following the NOAA Nino 3.4 forecast discussion.

Now we are beyond wondering if the Cool Event will meet La Nina Standards (it did not but that did not stop NOAA from declaring it to have been a reportable La Nina) and instead are wondering if the forecasted Warm Event will meet El Nino Standards.

Normally La Nina Conditions are confirmed by SOI 30 day values that are greater than or equal to +7.0. As you can see, that was not the case in October or November (not shown),  December, January, or February. It was the case in September. So any claims that the atmosphere was showing La Nina was Fake News by NOAA. Now you see the SOI threatening to be consistent with El Nino i.e. a negative value for the last 30 days.

And now we have the IRI/CPC March 16, 2017 fully model-based report.

Here is the discussion that was released with the IRI/CPC Report.

Published: March 16, 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 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 March 2017, the NINO3.4 SST anomaly remained in the neutral range, after having been at a borderline or weak La Niña levels during much of the second half of 2016.  For January the SST anomaly was 0.14 C, and for Dec-Feb it was -0.20 C. 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 -0.2, at an ENSO-neutral level. The SST farther east has been maintaining above-average levels for several months, making for a coastal El Niño during the rainy season in coastal Ecuador and northern Peru. Most of the pertinent atmospheric variables have also been assuming neutral patterns, with the exception of the convection anomalies in the central and western tropical Pacific, which have continued to suggest borderline La Niña conditions. The lower-level trade winds and upper level westerly winds have been largely near-average, although there are still weakly enhanced trade winds in the west-central part of the basin. The Southern Oscillation Index (SOI) has been near-average during the last couple of months. Subsurface temperature anomalies across the eastern equatorial Pacific have increased to near to slightly above average. Overall, given the SST and the atmospheric conditions, an ENSO-neutral diagnosis is in order.

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 is the most likely condition through northern spring 2017, with increasing chances (50 to 55%) for El Niño development during the summer or fall time frame. The latest set of model ENSO predictions, from mid-March, now available in the IRI/CPC ENSO prediction plume, is discussed below. Those predictions suggest that the SST is most likely to be in the ENSO-neutral range for March-May but with an increased likelihood for El Niño development from summer onward.

As of mid-March, 68% of the dynamical or statistical models predicts neutral ENSO conditions for the initial Mar-May 2017 season, while 32% 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 Jun-Aug 2017 season, among models that do use subsurface temperature information, no model predicts La Niña conditions, 72% predicts El Niño conditions, while 28% predicts neutral ENSO. For all model types, the probabilities for La Niña are 6% or less for for all predicted seasons from Mar-May 2017 through Nov-Jan 2016-17. The probability for El Niño conditions exceeds 50% beginning with Apr-June and lasting throughout the rest of 2017. The chances for El Niño rises to about 55% for Apr-Jun, 65% for May-Jul, between 70% and 75% for Jun-Aug and Jul-Sep, and approximately 80% from Aug-Oct through the final season of Nov-Jan 2017-18. Chances for neutral ENSO conditions drops from near 70% for Mar-May to below 50% thereafter, hovering between 10% and 30% from Jun-Aug through Nov-Jan 2017-18.

Note  – Only models that produce a new ENSO prediction every month are included in the above statement.

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 less than 10% from Mar-May through Oct-Dec 2017, increasing slightly to 11% for Nov-Jan 2017-18. Probabilities for ENSO-neutral are 77% for Mar-May 2017, falling steadily to 40% by May-Jul, and down to near 30% from Jul-Aug through Nov-Jan 2017-18. Probabilities for El Niño are 23% for Mar-May, rise to 45-50% by Apr-Jun and to approximately 60-68% for May-Jul through the final season of Nov-Jan 2017-18. 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 likelihood for neutral ENSO conditions for Mar-May 2017, and more weakly for Apr-Jun. Beginning with May-Jul, El Niño becomes more likely than neutral through the final season of Nov-Jan 2017-18. Although most likely, the chances for El Niño are not overwhelming, reaching approximately two-thirds or slightly higher from Jun-Aug through Nov-Jan 2017-18. Chances for La Niña are very 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 April by CPC and IRI, which will include some human judgment in combination with the model guidance.

I thought this was an interesting graphic.

Here is the recently released JAMSTEC Nino 3.4 Forecast.

Based on the Nino 3.4 projection, JAMSTEC is saying the Cool Event did not meet the criteria to have been declared a La Nina as was done by NOAA: Nino 3.4 being colder than -0.5 and the duration of being under -0.5 was not sufficient  to qualify as a La Nina. JAMSTEC is raising the possibility of a strong El Nino for the following winter. But it is too soon to make that prediction with a high degree of confidence.

The Discussion that goes with their Nino 3.4 forecast has now been released. Notice the suggestion that we might be having a Pacific Climate Shift to PDO Positive.

Mar. 21, 2017: Prediction from 1st Mar., 2017

ENSO forecast:

The SINTEX-F predicts that a moderate-to-strong El Niño event may start in early summer this year and reach its peak in winter. If this happens, it may suggest a decadal turnabout in the tropical Pacific climate condition to El Niño-like state after a long spell of La Niña-like state. Such natural climate variability may double the global warming impact as we observed during the period from 1976 through 1998. We need to be prepared well to this possible decadal climate regime shift.

Indian Ocean forecast:

Occurrence of a positive Indian Ocean Dipole is also clearly predicted by the SINTEX-F seasonal prediction system; the ensemble mean prediction suggests its evolution in summer and its height in fall. We may observe co-occurrence of a positive Indian Ocean Dipole and an El Niño in the latter half of 2017; this is just as we observed in 1997 and 2015.

Regional forecast:

On a seasonal scale, most part of the globe will experience a warmer-than-normal condition, while some parts of southern Canada and northern U. S., and northern Brazil will experience a colder-than-normal condition in the boreal spring. In the boreal summer, most parts of the globe will experience a hotter-than-normal condition. On the other hand, some parts of Europe, central Russia, and northern Australia will experience a cooler-than-normal condition.

As regards the seasonally averaged rainfall, a wetter-than-normal condition is predicted for western part of Brazil during the boreal spring, whereas most parts of southeastern China, Indonesia, eastern Brazil, southern Australia and Europe will experience a drier condition during the boreal spring. In the boreal summer, most parts of Indonesia, India, Australia, southeastern China, Mexico, and northern Brazil will experience a drier-than-normal condition, due to co-occurrence of the El Niño and the positive Indian Ocean Dipole.

Most parts of Japan will be in a warmer and drier-than-normal condition in the boreal spring. In boreal summer, we expect a wetter-than-normal and slightly hotter-than-normal condition due to development of the positive Indian Ocean Dipole and El Niño; El Niño influences may be cancelled due to development of the positive Indian Ocean Dipole and vice versa.

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

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  MAM, JJA, and SON to work with from JAMSTEC. So this month things do not line up perfectly for the first three-month period. In two out of three months they do not line up perfectly and this is one of the two months where it is not exactly the same three months. That should not make much difference.

In the past I showed the JAMSTEC forecast map first and commented on it and then I showed the NOAA map and commented on it and compared it to the JAMSTEC map that was above the NOAA map. Last month I changed the sequence and I am again showing the NOAA maps first.

MAM/AMJ 2017

Temperature (AMJ)

NOAA

JAMSTEC WORLD MAP (MAM) (Notice that the JAMSTEC Map is for MAM not AMJ as is the NOAA Map)

Precipitation

NOAA

And then to get more focus, I extracted and enlarged an image from the JAMSTEC map for CONUS (actually most of North America).. .

JAMSTEC WORLD MAP

JJA 2017 (and now both NOAA and JAMSTEC are addressing the same three-month period)

Temperature

NOAA

JAMSTEC WORLD MAP

Precipitation

NOAA

JAMSTEC CONUS (Extracted from the the JAMSTEC World Map and really including most of North America)

JAMSTEC WORLD MAP

SON 2017

Temperature

NOAA

JAMSTEC WORLD MAP

Precipitation

NOAA

JAMSTEC CONUS (Extracted from the JAMSTEC World Map and covering North America)

JAMSTEC WORLD MAP

Conclusion

Most of the differences with respect to CONUS can be explained by the differing forecasts for ENSO with JAMSTEC ramping up El Nino faster than NOAA and with more confidence than NOAA. But it is difficult to tell if the differences in the El Nino forecasts explain all of the differences between the two forecasts.