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Official 90-day Outlooks are issued once each month near mid-month at 8:30am Eastern Time. Please consult the schedule of 30 & 90-day outlooks for exact release dates.

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HOME> Outlook Maps>Seasonal Forecast Discussion
 
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.
$$

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