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HOME> Outlook Maps>Seasonal Forecast Discussion
 
PROGNOSTIC DISCUSSION FOR LONG-LEAD SEASONAL OUTLOOKS 
NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD
830 AM EDT THU AUG 18 2016

SUMMARY OF THE OUTLOOK FOR NON-TECHNICAL USERS

THE CURRENT OCEANIC AND ATMOSPHERIC STATE INDICATES ENSO-NEUTRAL CONDITIONS,
WITH A TRANSITION TO WEAK LA NINA CONDITIONS EXPECTED DURING THE AUG-SEP-OCT
(ASO) 2016 SEASON. THE LATEST CPC/IRI CONSENSUS ENSO FORECAST DEPICTS A
PROBABILITY OF 55-60 PERCENT FOR A WEAK LA NINA DURING THE AUTUMN AND EARLY
WINTER.

THE SON 2016 TEMPERATURE OUTLOOK INDICATES INCREASED PROBABILITIES OF
ABOVE-NORMAL TEMPERATURES ACROSS THE ENTIRE CONTIGUOUS U.S. AND ALASKA.
DYNAMICAL MODEL SUPPORT AND/OR HISTORICAL TRENDS FAVOR PROBABILITIES IN EXCESS
OF 50 PERCENT ACROSS THE SOUTHWESTERN STATES, GULF COAST REGION, THE EASTERN
GREAT LAKES AND NEW ENGLAND, AND THE NORTHERN AND SOUTHERN THIRDS OF ALASKA.
THE GREATEST PROBABILITIES OF ABOVE-NORMAL MEAN TEMPERATURES ARE IN EXCESS OF
70 PERCENT ACROSS THE NORTH SLOPE OF ALASKA. THIS IS LARGELY DUE TO WARMING
TRENDS OVER THE PAST FEW DECADES AND THE ASSOCIATED DELAYED ONSET OF SEA ICE
FORMATION (AND REDUCED COVERAGE OF MULTI-YEAR ICE) ACROSS THE NEARBY ARCTIC
OCEAN.

THE SON 2016 PRECIPITATION OUTLOOK INDICATES INCREASED PROBABILITIES OF
ABOVE-MEDIAN PRECIPITATION ACROSS THE NORTHERN GREAT PLAINS AND ALASKA
PANHANDLE, BASED PRIMARILY ON AVAILABLE CLIMATE MODEL GUIDANCE. BELOW-MEDIAN
PRECIPITATION IS FAVORED IN NEVADA AND ADJACENT PARTS OF CALIFORNIA, AS WELL AS
OVER THE LOWER MISSISSIPPI VALLEY, THE INTERIOR SOUTHEAST, TENNESSEE, THE
SOUTHERN APPALACHIANS, AND MUCH OF KENTUCKY. THIS IS BASED ON MODEL GUIDANCE,
AND ON HISTORICAL PRECIPITATION TRENDS FOR THE SON SEASON.

EQUAL CHANCES (EC) ARE FORECAST IN AREAS WHERE THE LIKELIHOOD OF SEASONAL MEAN
TEMPERATURES OR SEASONAL ACCUMULATED PRECIPITATION AMOUNTS ARE EXPECTED TO BE
SIMILAR TO CLIMATOLOGICAL PROBABILITIES.

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

PACIFIC SST ANOMALIES ARE MOSTLY 1-2 DEGREES C BELOW AVERAGE CLOSE TO THE
EQUATOR FROM ABOUT 170W EASTWARD TO 100W, WHILE ABOVE AVERAGE SSTS PREVAIL FROM
ABOUT 170E TO THE MARITIME CONTINENT. THE MOST RECENT THREE-MONTH AVERAGE NINO
3.4 SST ANOMALY IS +0.18 DEGREE C FOR MJJ. THE LATEST WEEKLY NINO 3.4 ANOMALY
HAS NOW DECREASED TO -0.5 DEGREE C. A LARGE RESERVOIR OF ANOMALOUSLY COOL
SUBSURFACE WATERS EXTENDS TO MORE THAN 150 METERS BELOW THE SURFACE, WITH THE
LARGEST NEGATIVE ANOMALIES 3-4 DEGREES C BELOW AVERAGE AT A DEPTH OF ABOUT 125
METERS, BETWEEN 140W-160W. POSITIVE OLR ANOMALIES (SUPPRESSED CONVECTION) WERE
PRESENT OVER THE EQUATORIAL PACIFIC, WHILE NEGATIVE OLR ANOMALIES (ENHANCED
CONVECTION) IS PRESENT OVER INDONESIA, DURING THE PAST 30-DAYS. LOW-LEVEL,
EASTERLY TRADE WINDS AT THE 850-HPA LEVEL HAVE BEEN NEAR AVERAGE DURING THE
PAST MONTH, WHILE THE UPPER-LEVEL, 200-HPA WINDS ARE ANOMALOUSLY WESTERLY OVER
THE EQUATORIAL PACIFIC FROM THE DATE LINE EASTWARD TO 150W. ANOMALOUS
INTEGRATED EQUATORIAL PACIFIC OCEAN HEAT CONTENT FROM THE SURFACE TO 300 METERS
DEPTH HAS BEEN PERSISTENTLY NEGATIVE FOR THE LAST SEVERAL MONTHS. NEGATIVE
OCEAN HEAT CONTENT ANOMALIES INCREASE THE CHANCE OF DEVELOPMENT OF LA NINA
CONDITIONS DURING THE REMAINDER OF 2016. THE EXTRATROPICAL PACIFIC OCEAN
REMAINS CONSISTENT WITH THE POSITIVE PHASE OF THE PACIFIC DECADAL OSCILLATION
(PDO) WITH ABOVE AVERAGE SSTS IN THE NORTH PACIFIC, AND TO THE SOUTH OF ALASKA,
AND ALONG THE COAST OF SOUTHERN CALIFORNIA. POSITIVE SST ANOMALIES PERSIST IN
THE WESTERN ATLANTIC NEAR THE U.S. EAST COAST, AND THE THE GULF OF MEXICO.

PROGNOSTIC DISCUSSION OF SST FORECASTS

THE CPC SST CONSOLIDATION PREDICTS A WEAK LA NINA BEGINNING IN ASO 2016 AND
CONTINUING THROUGHOUT THE AUTUMN AND MUCH OF WINTER, WITH A PEAK AMPLITUDE IN
SST ANOMALY OF -0.7 DEGREE C BELOW AVERAGE DURING THE DJF 2016-17 SEASON.
PREDICTIONS FROM THE NORTH AMERICAN MULTI-MODEL ENSEMBLE (NMME) MEMBERS
INDICATE A RANGE OF NINO 3.4 ANOMALIES, WITH THE ENSEMBLE MEAN NEAR -0.5 C FROM
AUGUST THROUGH DECEMBER. THE CPC/IRI CONSENSUS FORECAST INDICATES LA NINA IS
SLIGHTLY FAVORED TO DEVELOP DURING ASO 2016, WITH ABOUT A 55-60 PERCENT CHANCE
OF LA NINA DURING THE AUTUMN AND WINTER 2016-17.

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

CALIBRATED PROBABILISTIC FORECASTS FROM THE NMME PROVIDE THE PRIMARY GUIDANCE
FOR THE SEASONAL OUTLOOK FOR SON 2016. THE PREDICTED TRANSITION TO LA NINA
CONDITIONS AND THE MOST LIKELY IMPACTS ARE CONSIDERED FOR THE SEASONAL OUTLOOKS
PRIMARILY BEGINNING IN OND 2016 THROUGH THE WINTER INTO EARLY SPRING, 2017. IN
ADDITION TO DYNAMICAL MODEL GUIDANCE FROM THE NMME, THE SEASONAL OUTLOOKS ARE
ALSO BASED ON THE NCEP CLIMATE FORECAST SYSTEM (CFS), THE INTERNATIONAL
MULTI-MODEL ENSEMBLE (IMME), A SST-BASED CONSTRUCTED ANALOG AND OTHER
ADDITIONAL STATISTICAL TOOLS, INCLUDING REGRESSION-BASED IMPACTS OF ENSO, AND
DECADAL TRENDS INHERENT IN THE CPC CONSOLIDATION (CON) TOOL.

PROGNOSTIC DISCUSSION OF OUTLOOKS - SON 2016 TO SON 2017

TEMPERATURE

THE TEMPERATURE OUTLOOK FOR SON 2016 IS SIMILAR TO THE OUTLOOK MADE LAST MONTH
FOR THE SAME TARGET PERIOD. ABOVE NORMAL MEAN TEMPERATURES ARE FAVORED ACROSS
THE ENTIRE CONTIGUOUS UNITED STATES AND ALASKA. THE GREATEST PROBABILITIES FOR
THE CONUS INCLUDE THE SOUTHWESTERN STATES (IN EXCESS OF 60 PERCENT), THE GULF
COAST ENVIRONS AND FROM THE EASTERN GREAT LAKES TO THE NORTHERN ATLANTIC COAST
(IN EXCESS OF 50 PERCENT). FOR ALASKA, THE GREATEST PROBABILITIES OF ABOVE
NORMAL TEMPERATURES INCLUDE THE SOUTHERN THIRD OF THE STATE (IN EXCESS OF 60
PERCENT), AND THE NORTHERN THIRD OF ALASKA (GREATER THAN 70 PERCENT). THESE
AREAS ARE BASED ON THE LATEST AVAILABLE CLIMATE MODELS, SUCH AS THE CALIBRATED
PROBABILITIES FROM THE NATIONAL MULTI-MODEL ENSEMBLE (PAC), IMME, CFS, CANADIAN
MODELS, AND ON HISTORICAL TRENDS. A BROAD AREA OF SLIGHTLY ENHANCED
PROBABILITIES FOR ABOVE NORMAL TEMPERATURES (33-40 PERCENT) IS INDICATED FROM
THE FAR NORTHERN ROCKIES EASTWARD TO THE UPPER MISSISSIPPI VALLEY. THIS
REPRESENTS THE EARLY EFFECTS OF A DEVELOPING WEAK LA NINA.

THE TEMPERATURE OUTLOOKS FROM OND 2016 THROUGH AMJ 2017 INCLUDE THE ANTICIPATED
IMPACTS OF A WEAK LA NINA. APPROXIMATELY THE SOUTHERN HALF OF THE CONUS IS
FAVORED TO HAVE ABOVE NORMAL TEMPERATURES THROUGHOUT THESE LEADS, WITH THE
HIGHEST PROBABILITIES EXPECTED ACROSS THE SOUTHWESTERN STATES (IN EXCESS OF 50
PERCENT FROM OND 2016 THROUGH MAM 2017). CLIMATE MODELS AND HISTORICAL TRENDS
WERE ALSO INCORPORATED INTO THESE OUTLOOKS. FOR APPROXIMATELY THE NORTHERN HALF
OF THE CONUS, HOWEVER, A COMBINATION OF BELOW NORMAL TEMPERATURES AND EC IS
FAVORED THROUGHOUT THESE LEADS. STARTING IN OND, A SMALL AREA OF EC IS FAVORED
ACROSS THE NORTHERN GREAT PLAINS, AND ABOVE NORMAL TEMPERATURES ARE FAVORED
THROUGHOUT THE REMAINDER OF THE NORTHERN CONUS. THE HIGHEST PROBABILITIES (IN
EXCESS OF 40 PERCENT) ARE INDICATED OVER THE EASTERN GREAT LAKES AND THE
NORTHEAST, DUE TO A COMBINATION OF TEMPERATURE TRENDS AND CLIMATE MODEL
GUIDANCE. DURING NDJ, THE AREA OF PREDICTED EC EXPANDS EASTWARD AND
SOUTHEASTWARD TO INCLUDE MOST OF THE REMAINDER OF THE NORTHERN CONUS. THE
EXCEPTION IS NORTHERN NEW ENGLAND, WHERE LINGERING ABOVE NORMAL TEMPERATURES
ARE FAVORED. FROM DJF 2016-17 THROUGH AMJ 2017, AN AREA OF BELOW NORMAL
TEMPERATURES IS EXPECTED TO DEVELOP, INITIALLY OVER THE NORTHERN PLAINS AND
UPPER MISSISSIPPI VALLEY, FOLLOWED BY EASTWARD EXPANSION TO MICHIGAN AND
WESTWARD EXPANSION TO WASHINGTON AND OREGON DURING JFM AND FMA 2017. BY MAM AND
AMJ 2017, THE COVERAGE OF BELOW NORMAL TEMPERATURES IS EXPECTED TO DIMINISH IN
SIZE, WITH ABOVE NORMAL TEMPERATURES ANTICIPATED TO SHIFT INTO THE MID-ATLANTIC
AND SOUTHERN GREAT LAKES BY AMJ.

THE LATTER LEADS, MJJ THROUGH SON 2017, ARE PRIMARILY BASED ON LONGER-TERM
TEMPERATURE TRENDS, WITH ELEVATED PROBABILITIES OF ABOVE NORMAL TEMPERATURES
ACROSS MUCH OF THE CONUS.

IN ALASKA, HISTORICAL TEMPERATURE TRENDS AND MOST OF THE AVAILABLE CLIMATE
MODEL GUIDANCE FAVOR ABOVE NORMAL TEMPERATURES FOR THE FIRST TWO LEADS. THE
EXPECTATION OF A WEAK LA NINA FORMS THE BASIS FOR EC INCREASING IN COVERAGE
ACROSS THE SOUTHERN PORTION OF THE STATE DURING NDJ AND DJF. BELOW NORMAL
TEMPERATURES ARE FAVORED TO DEVELOP ACROSS THE PANHANDLE AND SOUTHEAST PART OF
THE MAINLAND DURING JFM AND FMA, AND ABOVE NORMAL TEMPERATURES ARE FORECAST TO
PERSIST OVER NORTHWESTERN ALASKA. FROM MAM TO SON 2017, THE ALASKA TEMPERATURE
OUTLOOK IS PRIMARILY ATTRIBUTED TO TRENDS, WITH ABOVE NORMAL TEMPERATURES
FAVORED INITIALLY ACROSS THE NORTH SLOPE DURING MAM AND AMJ, WHICH THEN EXPANDS
SOUTHWARD TO INCLUDE THE ENTIRE STATE BY JAS, ASO, AND SON 2017.

PRECIPITATION

THE PRECIPITATION OUTLOOKS ARE BASED ON CLIMATE MODEL GUIDANCE AND HISTORICAL
PRECIPITATION TRENDS, WITH TRENDS BEING ESPECIALLY FAVORED DURING THE LATTER
LEADS. IN SON, ABOVE MEDIAN PRECIPITATION IS PREDICTED ACROSS THE NORTHERN
PLAINS AND THE ALASKA PANHANDLE, WHILE BELOW MEDIAN PRECIPITATION IS EXPECTED
ACROSS NEVADA AND ADJACENT PARTS OF CALIFORNIA, AND MUCH OF THE SOUTHEASTERN
QUARTER OF THE CONUS. FROM OND 2016 THROUGH MAM 2017, THE ANTICIPATED IMPACTS
OF A WEAK LA NINA ARE DEPICTED. THESE IMPACTS INCLUDE ABOVE MEDIAN
PRECIPITATION EXPANDING WESTWARD TO INCLUDE THE NORTHERN ROCKIES AND PACIFIC
NORTHWEST, WHICH REDUCES IN SIZE BY FMA AND MAM TO INCLUDE THE PACIFIC
NORTHWEST. ABOVE MEDIAN PRECIPITATION IS ALSO FAVORED TO DEVELOP ACROSS THE
GREAT LAKES, OHIO VALLEY, EASTERN PORTIONS OF THE UPPER AND MIDDLE MISSISSIPPI
VALLEY, AND THE TENNESSEE VALLEY DURING THE DJF, JFM, AND FMA SEASONS. THIS WET
SIGNAL IS OFTEN OBSERVED DURING LA NINA WINTERS, AND USUALLY WINDS DOWN DURING
MAM AND AMJ. IN CONTRAST, BELOW MEDIAN PRECIPITATION IS FAVORED TO INCREASE IN
AREAL COVERAGE DURING OND AND NDJ TO INCLUDE MOST OF THE SOUTHERN CONUS. THIS
RELATIVELY DRY SIGNAL IS FORECAST TO CONTINUE ACROSS THE SOUTHERN STATES
THROUGH THE MAM SEASON, AS IS TYPICAL OF LA NINA WINTERS. BY AMJ 2017, THE
PRECIPITATION OUTLOOKS ARE BASED ALMOST EXCLUSIVELY ON HISTORICAL TRENDS AS
INDICATED BY THE CPC CONSOLIDATION TOOL. ABOVE MEDIAN PRECIPITATION IS FAVORED
ACROSS THE GREAT LAKES IN AMJ AND MJJ, WHICH SHIFTS EASTWARD TO THE NORTHEAST
STATES DURING JJA, JAS, AND ASO, WITH A RESIDUAL WET SIGNAL REMAINING OVER
MAINE BY SON 2017. DURING JJA AND JAS, A DRY TREND IS FAVORED OVER THE PACIFIC
NORTHWEST AND NORTHERN ROCKIES.

IN ALASKA, CLIMATE MODEL GUIDANCE GENERALLY SUPPORTS ABOVE MEDIAN PRECIPITATION
FOR THE PANHANDLE IN BOTH SON AND OND, WITH THE WET SIGNAL SHIFTING TO FAR
NORTHERN AND WESTERN ALASKA DURING THE SUBSEQUENT 3 SEASONS (NDJ, DJF, AND
JFM). BELOW MEDIAN PRECIPITATION IS FAVORED ACROSS THE SOUTHERN COAST OF
MAINLAND ALASKA FROM NDJ THROUGH JFM. THIS IS A COMMON FEATURE OF LA NINA
WINTERS. FOR FMA 2017 AND BEYOND, THERE IS NO DISCERNIBLE TILT IN THE ODDS
TOWARDS ANY ONE PRECIPITATION CATEGORY.

FORECASTER: ANTHONY ARTUSA

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/LONG_RANGE/TOOLS.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/PRODUCTS/SOILMST_MONITORING/US/OUTLOOK/OUTLOOK.SHTM
L
(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 15 2016


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

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