PROGNOSTIC DISCUSSION FOR LONG-LEAD SEASONAL OUTLOOKS
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
830AM EDT THURSDAY APR 16 2015

SUMMARY OF THE OUTLOOK FOR NON-TECHNICAL USERS

AN EL NINO ADVISORY REMAINS IN PLACE AS POSITIVE SEA SURFACE TEMPERATURE (SST) 
ANOMALIES ARE EVIDENT IN THE EQUATORIAL PACIFIC ALONG WITH EVIDENCE OF AN 
ATMOSPHERIC RESPONSE TO THESE WARMER THAN AVERAGE OCEAN TEMPERATURES. EL NINO 
CONDITIONS ARE FAVORED TO CONTINUE THROUGH AT LEAST THE BOREAL AUTUMN MONTHS.

THE MAY-JUNE-JULY (MJJ) 2015 TEMPERATURE OUTLOOK INDICATES ENHANCED 
PROBABILITIES OF ABOVE-NORMAL TEMPERATURES FOR ALASKA AND AREAS WEST OF THE 
ROCKY MOUNTAINS AND FAR SOUTHEAST, WITH PROBABILITIES OF BELOW-NORMAL 
TEMPERATURES ELEVATED FOR A REGION THAT INCLUDES PARTS OF THE SOUTHWEST AND 
SOUTHERN PLAINS.

FOR PRECIPITATION, ENHANCED PROBABILITIES OF ABOVE-MEDIAN PRECIPITATION ARE 
DEPICTED FOR MUCH OF THE GREAT BASIN, ROCKIES AND SOUTHWEST, EASTWARD ACROSS 
TEXAS TO INCLUDE PARTS OF THE SOUTHEAST, AS WELL AS PARTS OF ALASKA. 
BELOW-MEDIAN PRECIPITATION IS FAVORED FOR AN AREA NEAR THE WESTERN GREAT LAKES.

IN AREAS WHERE THE LIKELIHOODS OF SEASONAL MEAN TEMPERATURES AND SEASONAL 
ACCUMULATED PRECIPITATION AMOUNTS ARE SIMILAR TO CLIMATOLOGICAL PROBABILITIES, 
EQUAL CHANCES (EC) IS INDICATED.

BASIS AND SUMMARY OF THE CURRENT LONG-LEAD OUTLOOKS
NOTE:  FOR GRAPHICAL DISPLAYS OF THE FORECAST TOOLS DISCUSSED BELOW SEE:
HTTP://WWW.CPC.NCEP.NOAA.GOV/PRODUCTS/PREDICTIONS/90DAY/TOOLS/BRIEFING

CURRENT ATMOSPHERIC AND OCEANIC CONDITIONS

DURING MID-APRIL, SST ANOMALIES ACROSS THE ENTIRE EQUATORIAL CENTRAL AND 
EASTERN PACIFIC BASIN ARE AT LEAST +0.5C WITH SOME AREAS NEAR THE DATE LINE AND 
JUST OFF THE SOUTH AMERICAN COAST GREATER THAN 2.0 DEGREES ABOVE AVERAGE. THE 
LATEST NINO3.4 VALUE IS +0.7C. AT DEPTH, THERE IS CURRENTLY A LARGE RESERVOIR 
OF ABOVE-AVERAGE OCEAN TEMPERATURES FROM 160E TO THE SOUTH AMERICA COAST TO 
NEARLY A DEPTH OF 200 M IN SOME LOCATIONS (NEAR 160W). A STRONG, SLOW MOVING 
DOWNWELLING OCEANIC KELVIN WAVE CONTINUES TO BE EVIDENT ACROSS THE EASTERN 
PACIFIC PORTION OF THE BASIN. THE OVERALL ANOMALOUS OCEANIC HEAT CONTENT FROM 
THE SURFACE TO A DEPTH OF 300 METERS FROM THE DATE LINE TO 100W IS STRONGLY 
POSITIVE RUNNING AT +1.8C. THE POSITIVE SUBSURFACE HEAT ANOMALY PROVIDES A 
SOURCE OF WARMER-THAN-AVERAGE OCEAN WATER FOR CONTINUATION OF POSITIVE SURFACE 
TEMPERATURE ANOMALIES FOR THE NEXT SEVERAL SEASONS.     

ANOTHER IMPORTANT FEATURE THAT IMPACTED THE OUTLOOK IS THE PATTERN OF SSTS 
ACROSS THE EXTRATROPICAL PACIFIC WHICH CONTINUES TO SHOW LARGE POSITIVE 
ANOMALIES (BETWEEN 2-3 DEGREES ABOVE NORMAL IN SOME AREAS) FROM JUST SOUTH OF 
ALASKA EASTWARD AND SOUTHWARD ALONG THE WEST COAST OF NORTH AMERICA TO HAWAII. 
THIS SST PATTERN CONTINUES TO PROJECT VERY STRONGLY ONTO A POSITIVE PDO 
PATTERN. IN FACT THE MARCH 2015 VALUE WAS +2.0, CONTINUING A TREND OF RECORD 
AND NEAR RECORD MONTHLY POSITIVE PDO VALUES SEEN THIS PAST WINTER AND EARLY 
SPRING. 

THE ATMOSPHERIC RESPONSE TO EQUATORIAL SSTS HAS BECOME MORE ROBUST IN THE LAST 
MONTH OR TWO. ENHANCED CONVECTION NEAR THE DATE LINE HAS PERSISTED SINCE EARLY 
MARCH WITH A CORRESPONDING AREA OF SUPPRESSED CONVECTION TO THE WEST OVER 
INDONESIA. LOW-LEVEL WESTERLY WIND ANOMALIES AT 850 HPA HAVE BEEN MORE 
CONSISTENTLY OBSERVED OVER THE CENTRAL EQUATORIAL PACIFIC DURING THE PAST TWO 
MONTHS. AT UPPER LEVELS, ANOMALOUS WINDS NOW INDICATE ANTI-CYCLONIC 
CIRCULATIONS SYMMETRIC ABOUT THE EQUATOR NEAR THE DATE LINE, A RESPONSE 
CONSISTENT WITH EL NINO AND ITS ASSOCIATED PERSISTENT TROPICAL FORCING. 

THESE COMBINED OCEANIC AND ATMOSPHERIC CONDITIONS TAKEN TOGETHER INDICATE EL 
NINO CONDITIONS REMAIN IN PLACE AND ARE LIKELY STRENGTHENING.

PROGNOSTIC DISCUSSION OF SST FORECASTS

IN GENERAL, THERE HAS BEEN AN INCREASE TOWARD HIGHER PREDICTED VALUES OF 
NINO3.4 SST ANOMALY FROM BOTH STATISTICAL AND DYNAMICAL MODELS SINCE THIS TIME 
LAST MONTH. THE CPC NINO3.4 SST ANOMALY CONSOLIDATION FORECAST SHOWS A GRADUAL 
INCREASE FROM JUST ABOVE +0.5C IN LATE SPRING TO A PEAK OF JUST OVER +1.0C BY 
THE OND SEASON, GRADUALLY DECREASING THEREAFTER. MOST DYNAMICAL MODEL FORECASTS 
INDICATE A MORE MARKED INCREASE OVER THIS SAME PERIOD WITH VALUES CONTINUING TO 
INCREASE AND REACHING GREATER THAN +1.5C SST ANOMALY BY THE MONTH OF NOVEMBER, 
DEPICTING AN EVENTUAL STRONG-CATEGORY EL NINO EVENT. MANY STATISTICAL MODEL 
FORECASTS, HOWEVER, MAINTAIN A WEAK EVENT (LESS THAN +0.5C). IT IS IMPORTANT TO 
NOTE THAT ONLY A HANDFUL OF MODELS DEPICT NO EL NINO EVENT OF ANY KIND OVER THE 
REMAINDER OF 2015.

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

THE PRIMARY TOOLS THAT WERE CONSIDERED IN MAKING THE SEASONAL TEMPERATURE AND 
PRECIPITATION OUTLOOKS THROUGH SEPTEMBER-OCTOBER-NOVEMBER 2015 INCLUDED OUTPUT 
FROM THE NMME AND IMME AND THEIR MEMBER MODELS AND CORRELATIONS BETWEEN 
SEASONAL MEAN TEMPERATURE OR TOTAL PRECIPITATION AND SEASONAL NINO3.4 AND PDO 
INDICES.  THE LATTER WAS UTILIZED FOR MANY OF THE OUTLOOK SEASONS INCLUDING AT 
TIMES DURING THE WARM SEASON, BUT ESPECIALLY FOR LATE AUTUMN 2015 AND THE 
UPCOMING WINTER. THE CONSTRUCTED ANALOGUE BASED ON GLOBAL SST AND SOIL MOISTURE 
WAS ALSO CONSIDERED. POTENTIAL IMPACTS OF INTERANNUAL MODES OF CLIMATE 
VARIABILITY WERE UTILIZED THROUGH THE FEBRUARY-MARCH-APRIL (FMA) 2016 PERIOD. 
THEREAFTER, THE CON WAS PRIMARILY UTILIZED WHICH DERIVES CLIMATE SIGNALS 
PRIMARILY FROM DECADAL CLIMATE TRENDS.

PROGNOSTIC DISCUSSION OF OUTLOOKS - MJJ 2015 TO MJJ 2016

TEMPERATURE

THE MJJ 2015 TEMPERATURE OUTLOOK DEPICTS ELEVATED ODDS FOR ABOVE NORMAL 
SEASONAL MEAN TEMPERATURES FOR MOST AREAS WEST OF THE ROCKY MOUNTAINS, ALL OF 
ALASKA AS WELL AS PORTIONS OF THE SOUTHEAST CONUS. THE FORECAST PATTERN FOR 
REGIONS FAVORING ABOVE NORMAL TEMPERATURE IS A PERSISTENT SIGNAL AND IS IN THE 
OUTLOOKS THROUGH THE SON 2015 SEASON. THERE IS STRONG SUPPORT FROM 
PROBABILISTIC MODEL GUIDANCE OF THE NMME FOR THESE AREAS AS WELL AS SOME 
SUPPORT FROM PDO AND NINO3.4 CORRELATIONS IN SOME AREAS AND SEASONS. THE 
GREATEST PROBABILITIES, AS IN PREVIOUS OUTLOOKS, REMAINS ALONG THE WEST COAST 
AND FOR SOUTHERN ALASKA WHERE THE PATTERN OF LARGE SCALE SSTS HAS BEEN A STRONG 
CLIMATE INFLUENCE. 

BELOW NORMAL SEASONAL MEAN TEMPERATURES ARE INDICATED DURING MJJ AND JJA 2015 
FOR PARTS OF THE SOUTHWEST AND SOUTHERN PLAINS PRIMARILY BASED ON PDO 
CORRELATIONS AND SOME DYNAMICAL MODEL GUIDANCE OUTPUT. LATER IN THE SUMMER 
MONTHS, FAVORED BELOW NORMAL TEMPERATURES ARE INTRODUCED IN THE INTERIOR OF OF 
THE CONUS ASSOCIATED WITH CORRELATIONS WITH EL NINO. THIS AREA SLOWLY SHIFTS 
SOUTH AND WEST WITH TIME SO THAT BY THE AUTUMN (OND 2015) THERE ARE ELEVATED 
ODDS FOR BELOW NORMAL TEMPERATURES ACROSS PARTS OF THE SOUTHWEST AND SOUTHERN 
PLAINS BY OND 2015. IT WAS DECIDED THAT SOME OF THE MODEL GUIDANCE FOR FAVORED 
ABOVE NORMAL TEMPERATURES FROM THE NMME ACROSS THE INTERIOR OF THE CONUS WAS 
OVERDONE GIVEN THE PATTERN OF SSTS ACROSS BOTH THE TROPICS AND EXTRATROPICS IN 
THE PACIFIC BASIN. THIS DOES RESULT IN A CHANGE IN THE OUTLOOKS (EC DEPICTED) 
FOR PARTS OF THE EASTERN CONUS FROM PREVIOUS OUTLOOKS WHICH LAST MONTH FAVORED 
ABOVE NORMAL TEMPERATURES.  

FOR THE SEASONS NDJ 2015-16 THROUGH FMA 2016, CLASSIC WINTERTIME EL NINO 
IMPACTS ARE DEPICTED ON THE OUTLOOK MAPS, ALBEIT WITH LOW PROBABILITIES. THIS 
INCLUDES FAVORED ABOVE NORMAL TEMPERATURES FOR ALASKA, AND ALONG THE NORTHERN 
TIER OF THE CONUS FROM THE PACIFIC NORTHWEST TO THE GREAT LAKES. BELOW NORMAL 
TEMPERATURES ARE MORE LIKELY ACROSS PORTIONS OF THE SOUTHERN CONUS DURING EL 
NINO EVENTS. THE CON WAS THE DRIVER FOR THE OUTLOOKS BEYOND THIS PERIOD WHICH 
ARE LARGELY INFLUENCED BY LONG TERM TEMPERATURE TRENDS.

PRECIPITATION

THE MJJ 2015 PRECIPITATION OUTLOOK DEPICTS ELEVATED ODDS FOR ABOVE MEDIAN 
SEASONAL TOTAL PRECIPITATION FOR PARTS OF SOUTHERN AND INTERIOR ALASKA, MUCH OF 
THE GREAT BASIN, ROCKIES AND SOUTHWEST, AND EASTWARD ALONG THE SOUTHERN TIER OF 
THE CONUS TO INCLUDE PARTS OF THE SOUTHEAST. CORRELATIONS WITH PDO AND NINO3.4 
INDICES ALONG WITH DYNAMICAL MODEL GUIDANCE SUPPORT THE FORECAST IN THE WEST 
AND FOR ALASKA WHILE MODEL GUIDANCE WAS THE PRIMARY DRIVER FOR THE OUTLOOK IN 
THE SOUTHEAST. BELOW MEDIAN PRECIPITATION IS MORE LIKELY FOR AREAS IN CLOSE 
PROXIMITY TO THE WESTERN GREAT LAKES BASED ON DYNAMICAL MODEL GUIDANCE. 

ABOVE MEDIAN PRECIPITATION REMAINS FAVORED FOR MUCH OF THE WESTERN U.S. 
INCLUDING THE SOUTHWEST MONSOON REGION THROUGH ASO 2015 BASED ON CORRELATIONS 
WITH PDO AND NINO3.4 AND FURTHER SUPPORTED BY DYNAMICAL MODEL GUIDANCE. BELOW 
MEDIAN PRECIPITATION IS INTRODUCED IN THE FAR PACIFIC NORTHWEST IN JJA 2015 AND 
EXPANDS TO INCLUDE PORTIONS OF THE NORTHERN ROCKIES BY OND 2015. BOTH PDO AND 
EL NINO CORRELATIONS SUPPORT BELOW MEDIAN PRECIPITATION FOR AREAS OF THE 
MID-ATLANTIC IN JAS AND ASO 2015.  

AS THE OUTLOOKS PROCEED FROM OND 2015, THE TYPICAL WINTERTIME EL NINO IMAPCTS 
ARE INTRODUCED INTO THE OUTLOOKS (THROUGH FMA 2016), ALBEIT AT LOW 
PROBABILITIES. THESE INCLUDE FAVORED ABOVE MEDIAN PRECIPITATION ALONG THE 
SOUTHERN TIER OF THE CONUS AND FAVORED BELOW MEDIAN PRECIPITATION FOR PORTIONS 
OF THE NORTHERN ROCKIES FROM NDJ 2015-16 THROUGH FMA 2016 AND FOR PARTS OF THE 
OHIO VALLEY AND GREAT LAKES DURING THE DJF 2015-16 THROUGH FMA 2016 SEASONS. 

FORECASTER: JON GOTTSCHALCK

THE CLIMATIC NORMALS ARE BASED ON CONDITIONS BETWEEN 1981 AND 2010, FOLLOWING 
THE WORLD METEROLOGICAL ORGANIZATION CONVENTION OF USING THE MOST RECENT 3 
COMPLETE DECADES AS THE CLIMATIC REFERENCE PERIOD.  THE PROBABILITY ANOMALIES 
FOR TEMPERATURE AND PRECIPITATION BASED ON THESE NEW NORMALS BETTER REPRESENT 
SHORTER TERM CLIMATIC ANOMALIES THAN THE FORECASTS BASED ON OLDER NORMALS.

FOR A DESCRIPTION OF OF THE STANDARD FORECAST TOOLS - THEIR SKILL- AND THE
FORECAST FORMAT PLEASE SEE OUR WEB PAGE AT
HTTP:/WWW.CPC.NCEP.NOAA.GOV/PRODUCTS/PREDICTIONS/90DAY/DISC.HTML
(USE LOWER CASE LETTERS)
INFORMATION ON THE FORMATION OF SKILL OF THE CAS FORECASTS MAY BE FOUND AT:
HTTP://WWW.CPC.NCEP.NOAA.GOV/SOILMST/FORECASTS.HTML (USE LOWERCASE LETTERS)
NOTES - THESE CLIMATE OUTLOOKS ARE INTENDED FOR USE PRIOR TO THE START OF THEIR 
VALID PERIOD.  WITHIN ANY GIVEN VALID PERIOD OBSERVATIONS AND SHORT AND MEDIUM 
RANGE FORECASTS SHOULD BE CONSULTED.

THIS SET OF OUTLOOKS WILL BE SUPERSEDED BY THE ISSUANCE OF THE NEW SET NEXT 
MONTH ON MAY 21 2015


1981-2010 BASE PERIOD MEANS WERE IMPLEMENTED EFFECTIVE WITH THE MAY 19, 2011 
FORECAST RELEASE.
$$