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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 AUG 20 2015

SUMMARY OF THE OUTLOOK FOR NON-TECHNICAL USERS

RECENT OBSERVATIONS OF SEA-SURFACE AND SUBSURFACE TEMPERATURES, LOWER- AND
UPPER-LEVEL WINDS, AND PRECIPITATION PATTERNS ACROSS THE EQUATORIAL PACIFIC
INDICATE AN ONGOING EL NINO. IN THE NORTHERN HEMISPHERE, THIS WARM EVENT IS
EXPECTED TO REACH ITS PEAK INTENSITY (STRONG EL NINO) BY LATE AUTUMN, WITH SLOW
WEAKENING THROUGHOUT THE WINTER AND EARLY SPRING (2016).

THE SEPTEMBER-OCTOBER-NOVEMBER (SON) 2015 TEMPERATURE OUTLOOK INDICATES
ENHANCED PROBABILITIES OF ABOVE-NORMAL TEMPERATURES FOR THE WESTERN CONTIGUOUS
U.S., WITH PROBABILITIES REACHING OR EXCEEDING 60 PERCENT IN THE PACIFIC
NORTHWEST. ABOVE-NORMAL TEMPERATURES ARE ALSO FAVORED ALONG THE EASTERN
SEABOARD, EAST GULF COAST REGION, AND ALASKA, WITH PROBABILITIES REACHING OR
EXCEEDING 70 PERCENT FOR THE NORTH SLOPE OF ALASKA. BELOW-NORMAL TEMPERATURES
ARE FAVORED ACROSS SOUTH-CENTRAL PORTIONS OF BOTH THE GREAT PLAINS AND
MISSISSIPPI VALLEY.

THE SON 2015 PRECIPITATION OUTLOOK INDICATES ENHANCED PROBABILITIES OF
ABOVE-MEDIAN PRECIPITATION AMOUNTS FOR THE SOUTHEASTERN HALF OF CALIFORNIA, THE
SOUTHWEST, THE CENTRAL AND SOUTHERN ROCKIES, MOST OF THE GREAT PLAINS, FROM THE
LOWER MISSISSIPPI VALLEY EASTWARD ACROSS THE INTERIOR SOUTHEAST AND THE
TENNESSEE VALLEY, AND ACROSS SOUTHERN ALASKA. ODDS FAVOR BELOW-MEDIAN
PRECIPITATION AMOUNTS FOR THE PACIFIC NORTHWEST, AND FROM THE NORTHERN GREAT
LAKES EASTWARD ACROSS NEW YORK AND NEW ENGLAND.

IN THE SUBSEQUENT SEASONS, THE OUTLOOK SLOWLY CHANGES TO REFLECT MORE CANONICAL
ENSO IMPACTS AS WE HEAD TOWARD METEOROLOGICAL WINTER.

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

SSTS NEAR AND ALONG THE EQUATORIAL PACIFIC RANGE BETWEEN 1-4 DEGREES C ABOVE
THE LONG-TERM AVERAGE FROM ABOUT THE INTERNATIONAL DATE LINE EASTWARD TO THE
SOUTH AMERICAN COAST. WEST OF THE DATE LINE IN THE EQUATORIAL PACIFIC, SSTS ARE
NEAR-, OR SLIGHTLY BELOW-, AVERAGE. SUBSURFACE WATER TEMPERATURES FROM NEAR THE
DATE LINE EASTWARD TO THE SOUTH AMERICAN COAST, AND DOWN TO ABOUT 200 METERS,
ARE ANYWHERE FROM 1-6 DEGREES C ABOVE AVERAGE. THIS SUBSURFACE VOLUME OF
ANOMALOUSLY WARM WATER PROVIDES A RESERVOIR OF POTENTIAL HEAT ENERGY TO HELP
SUSTAIN THE CURRENT EL NINO. WEST OF THE DATE LINE IN THE NEAR-EQUATORIAL
PACIFIC, EXTENDING DOWN TO 200 METERS, WATER TEMPERATURES RANGE FROM 0.5-2.5
DEGREES C BELOW AVERAGE.

ATMOSPHERIC CONDITIONS ACROSS THE TROPICAL PACIFIC CONTINUE TO BE CONSISTENT
WITH A SIGNIFICANT AND STRENGTHENING EL NINO. UPPER-LEVEL (200-HPA) WIND
ANOMALIES ARE PRIMARILY WESTERLY OVER THE EASTERN PACIFIC, CENTRAL AMERICA, AND
THE CARIBBEAN SEA, WHICH HAS HELPED TO SUPPRESS THE DEVELOPMENT OF TROPICAL
CYCLONES IN THE ATLANTIC BASIN THIS SEASON. LOWER-LEVEL (850-HPA) WIND
ANOMALIES ARE ALSO WESTERLY, ACROSS A LARGE PORTION OF THE TROPICAL PACIFIC,
FROM ABOUT 150E TO 140W. OUTGOING LONGWAVE RADIATION (OLR) ANOMALIES FOR THE
PAST MONTH INFER A RAINFALL DISTRIBUTION THAT IS VERY CONSISTENT WITH A MATURE
EL NINO. ENHANCED CONVECTION WAS NOTED FROM ABOUT 160E ALONG AND JUST NORTH OF
THE EQUATOR TO COSTA RICA AND PANAMA, WHILE SUPPRESSED CONVECTION WAS NOTED
ACROSS THE FAR WESTERN PACIFIC AND INDONESIA.

THE EXTRA-TROPICAL PACIFIC OCEAN REMAINS CONSISTENT WITH THE POSITIVE PHASE OF
THE PACIFIC DECADAL OSCILLATION (PDO), WITH THE MONTHLY INDEX AT +1.84 IN JULY,
AS DOCUMENTED BY THE UNIVERSITY OF WASHINGTON. THIS MAY HAVE SOME IMPACT ON
CONDITIONS NEAR THE WEST COAST OF NORTH AMERICA, ESPECIALLY THROUGH EARLY
AUTUMN.

PROGNOSTIC DISCUSSION OF SST FORECASTS

MOST DYNAMICAL MODELS THAT PREDICT NINO 3.4 SST ANOMALIES CONTINUE TO FAVOR A
PEAK DEPARTURE DURING THE LATE FALL. THE CPC SST CONSOLIDATION FORECASTS A
MAXIMUM IN NINO 3.4 SST ANOMALIES OF +2.3 DEGREES C DURING NDJ 2015/16, WITH A
SLOW DECREASE IN MAGNITUDE THEREAFTER. IT REMAINS ABOVE +1.0 C THROUGH FMA
2016. THE CFS MODEL IS AMONG THE WARMEST OF SOLUTIONS, WITH ENSEMBLE MEMBERS
PREDICTING ANOMALIES OF 2-3 DEGREES C ABOVE AVERAGE, WITH THE ENSEMBLE MEAN
VALUE TOPPING OUT DURING OND NEAR +2.5 C. THE NMME PLUME FORECASTS A FAIRLY
DISPERSIVE DISTRIBUTION OF ENSEMBLE MEMBERS, RANGING FROM 1-3 DEGREES C
ABOVE-AVERAGE, WITH THE ENSEMBLE MEAN PEAK IN DECEMBER OF +2.0 DEGREES C. THE
CPC-IRI CONSENSUS PROBABILISTIC ENSO FORECAST DEPICTS ODDS GREATER THAN 90
PERCENT FOR EL NINO TO CONTINUE THROUGHOUT BOREAL WINTER, AND ABOUT 85 PERCENT
INTO EARLY SPRING 2016.

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

THE SERIES OF OUTLOOKS FROM SON 2015 THROUGH JFM 2016 UTILIZE A COMBINATION OF
DYNAMICAL AND STATISTICAL MODELS, SUCH AS THE CFS, NMME, IMME, SST CONSTRUCTED
ANALOGS, SMLR, CCA, OCN, IRI, AND THE CON. ENSO COMPOSITES FOR PREVIOUS STRONG
EL NINOS WERE ALSO USED IN THE FORMULATION OF THE OUTLOOK MAPS THROUGHOUT THE
AUTUMN AND WINTER SEASONS. OUTLOOKS FOR SUBSEQUENT SEASONS ARE BASED PRIMARILY
ON LONG-TERM, HISTORICAL TEMPERATURE AND PRECIPITATION TRENDS, AS INDICATED BY
THE CON TOOL.

PROGNOSTIC DISCUSSION OF OUTLOOKS - SON 2015 TO SON 2016

TEMPERATURE

THE SON 2015 TEMPERATURE OUTLOOK RELIES PRIMARILY ON NMME OUTPUT, THE CFS,
IMME, SST CONSTRUCTED ANALOGS, AND TO A LESSER DEGREE EL NINO COMPOSITES. ABOVE
-NORMAL TEMPERATURES ARE FAVORED FOR THE WESTERN CONTIGUOUS U.S., WITH
PROBABILITIES REACHING OR EXCEEDING 60 PERCENT IN THE PACIFIC NORTHWEST. EL
NINO AND POSITIVE PDO EVENTS FAVOR ABOVE-NORMAL TEMPERATURES ALONG PRACTICALLY
THE ENTIRE WEST COAST OF NORTH AMERICA. ABOVE-NORMAL TEMPERATURES ARE ALSO
FAVORED ALONG THE EASTERN SEABOARD AND EAST GULF COAST REGION, BASED MOSTLY ON
THE CFS AND NMME. MOST MODELS AGREE ON ELEVATED ODDS FOR ABOVE-NORMAL
TEMPERATURES IN ALASKA, WITH PROBABILITIES REACHING OR EXCEEDING 70 PERCENT
ACROSS THE NORTH SLOPE AREA. THESE HIGHER PROBABILITIES ARE ALSO SUPPORTED BY
MORE RECENT TRENDS (LAST 10-15 YEARS) IN THE REDUCTION AND/OR DELAY OF SEA ICE
ONSET. BELOW-NORMAL TEMPERATURES ARE FAVORED ACROSS SOUTH-CENTRAL PORTIONS OF
BOTH THE GREAT PLAINS AND MISSISSIPPI VALLEY. THIS IS BASED ON DYNAMICAL MODELS
SUCH AS THE CFS, NMME, AND IMME, AS WELL AS STATISTICS FROM THE SST CONSTRUCTED
ANALOGS.

AS THE FORECASTS PROGRESS THROUGH THE AUTUMN AND INTO WINTER, THE PATTERN
SLOWLY MORPHS TO ONE CONSISTENT WITH STRONG EL NINO CONDITIONS, LARGELY
FAVORING BELOW-NORMAL TEMPERATURES ACROSS THE SOUTH-CENTRAL AND SOUTHEAST
CONUS, WITH ABOVE-NORMAL TEMPERATURES ACROSS THE NORTHERN TIER. PROBABILITIES
OF BELOW-NORMAL TEMPERATURES ACROSS THE SOUTHERN GREAT PLAINS REACH OR EXCEED
50 PERCENT IN DJF, JFM, AND FMA 2016. PROBABILITIES OF ABOVE-NORMAL
TEMPERATURES REACH OR EXCEED 60 PERCENT ACROSS THE PACIFIC NORTHWEST AND THE
UPPER MISSISSIPPI VALLEY IN DJF. IN DJF AND JFM, THE EXPECTATION OF A STRONG EL
NINO FAVORS ELEVATED PROBABILITIES OF ABOVE-NORMAL TEMPERATURES ACROSS THE
CENTRAL MISSISSIPPI AND OHIO VALLEYS, WITH A CORRESPONDING SOUTHWARD SHIFT OF
FAVORED BELOW-NORMAL TEMPERATURES. IN GENERAL, PROBABILITIES FOR ABOVE-NORMAL
TEMPERATURES WERE INCREASED SLIGHTLY FROM THE CORRESPONDING PREVIOUS SET OF
OUTLOOKS ACROSS THE NORTHWESTERN AND NORTH-CENTRAL CONUS, IN ACCORDANCE WITH
MORE CONFIDENCE IN A STRONG EL NINO BY LATE AUTUMN AND WINTER. BY FMA,
PREDICTED ANOMALIES ARE STILL ROBUST, THOUGH THERE IS A NOTICEABLE DECLINE IN
BOTH AREAL COVERAGE AND ANOMALY MAGNITUDES FORECAST DURING MAM AND AMJ 2016. BY
SUMMER 2016, THE TRENDS TOWARD ABOVE-NORMAL TEMPERATURES BEGIN TO GAIN
INFLUENCE AS THE WANING EL NINO LOSES INFLUENCE, SO THE FORECAST REFLECTS THE
CPC CONSOLIDATION AND TRENDS.

PRECIPITATION

THE SON 2015 PRECIPITATION OUTLOOK INDICATES ENHANCED PROBABILITIES OF
ABOVE-MEDIAN PRECIPITATION AMOUNTS FOR THE SOUTHEASTERN HALF OF CALIFORNIA, THE
SOUTHWEST, THE CENTRAL AND SOUTHERN ROCKIES, MOST OF THE GREAT PLAINS EXTENDING
EASTWARD ACROSS THE LOWER MISSISSIPPI AND TENNESSEE VALLEYS, THE INTERIOR
SOUTHEAST, AND SOUTHERN ALASKA. THESE ANOMALIES ARE CONSISTENT WITH HISTORICAL
WARM ENSO EVENTS. THE NMME, IMME, CFS, AND SST CONSTRUCTED ANALOGS ALSO SUPPORT
THIS PATTERN. THE EASTWARD EXTENSION OF FAVORED ABOVE-MEDIAN PRECIPITATION
ACROSS THE INTERIOR SOUTHEAST TENDS TO SHOW UP IN PAST STRONG EL NINOS,
ESPECIALLY LATER IN THE SON SEASON. ODDS FAVOR BELOW-MEDIAN PRECIPITATION
AMOUNTS OVER THE PACIFIC NORTHWEST, AND FROM THE NORTHERN GREAT LAKES EASTWARD
ACROSS NEW YORK AND NEW ENGLAND. THE FORMER REGION (PACIFIC NORTHWEST) ALSO HAS
SUBSTANTIAL SUPPORT FROM THE VARIOUS CLIMATE MODELS. THESE PRECIPITATION
SIGNALS ARE ALSO WELL SUPPORTED BY ENSO COMPOSITES FOR SON.

FOR OND AND NDJ, PAST EL NINOS HAVE FAVORED THE EASTWARD EXTENSION OF THE
SUBTROPICAL JET STREAM ACROSS THE SOUTHERN CONUS. ACCORDINGLY, THE AREA OF
PREDICTED ABOVE-MEDIAN PRECIPITATION HAS ALSO BEEN EXTENDED EASTWARD TO THE
SOUTHERN ATLANTIC COAST, WITH PROBABILITIES AT OR ABOVE 50 PERCENT IN FLORIDA
IN NDJ. ABOVE-MEDIAN PRECIPITATION IS FAVORED IN SOUTHERN ALASKA DURING OND.
THE TWIN AREAS OF PREDICTED BELOW-MEDIAN PRECIPITATION, ONE IN THE NORTHWEST,
AND THE OTHER IN THE NORTHEAST/GREAT LAKES REGION, ARE ALSO CONSISTENT WITH EL
NINO COMPOSITES. DURING OND AND NDJ, THERE IS A PREFERRED TENDENCY FOR THE
RELATIVE DRYNESS ACROSS THE NORTHWEST TO EXPAND EASTWARD, AND FOR THE RELATIVE
DRYNESS ACROSS THE NORTHEAST AND GREAT LAKES AREA TO CONSOLIDATE ACROSS THE
LATTER REGION.

FOR DJF 2015/16 AND JFM 2016, THE FORECAST ANOMALIES REACH THEIR PEAK STRENGTH,
WITH PROBABILITIES FOR ABOVE-MEDIAN PRECIPITATION AMOUNTS REACHING OR EXCEEDING
60 PERCENT IN FLORIDA AND FAR SOUTHERN SECTIONS OF BOTH CALIFORNIA AND ARIZONA
IN JFM. THE AREAS OF ANTICIPATED BELOW-MEDIAN PRECIPITATION ACROSS THE
NORTHWEST AND FROM THE GREAT LAKES SOUTHWARD INTO THE TENNESSEE VALLEY REACH
MATURITY DURING THESE TWO SEASONS. ODDS FOR BELOW-MEDIAN PRECIPITATION ARE ALSO
ELEVATED ACROSS SOUTHWESTERN ALASKA IN DJF AND JFM, DUE MAINLY TO THE NMME,
CFS, SST CONSTRUCTED ANALOGS, IMME, AND IRI PROJECTIONS.

PREDICTED ANOMALIES ARE STILL PRONOUNCED DURING FMA, THOUGH IN MAM THERE IS A
NOTABLE DECLINE IN BOTH AREAL COVERAGE AND ANOMALY MAGNITUDES, WHICH
CORRESPONDS TO THE EXPECTED WINDING DOWN OF THE CURRENT WARM EVENT. FROM AMJ
ONWARD (COINCIDENT WITH THE SPRING BARRIER), THERE IS SIGNIFICANT UNCERTAINTY
AS TO WHETHER OR NOT A LA NINA DEVELOPS, AND IF SO, ITS EXPECTED INTENSITY.
THEREFORE, EC IS FORECAST FOR THE REMAINING PRECIPITATION OUTLOOKS.

FORECASTER: CPC FORECASTER

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 SEP 17 2015


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

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