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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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    0.5mn SON 2018
    1.5mn OND 2018
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    4.5mn JFM 2019
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    6.5mn MAM 2019
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    0.5mn Sep 2018


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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 16 2018

SUMMARY OF THE OUTLOOK FOR NON-TECHNICAL USERS

THE SEPTEMBER-OCTOBER-NOVEMBER (SON) 2018 TEMPERATURE OUTLOOK INDICATES LIKELY
ABOVE NORMAL TEMPERATURES ACROSS A MAJORITY OF THE FORECAST DOMAIN, ALTHOUGH
EQUAL CHANCES OF BELOW, NEAR, OR ABOVE NORMAL TEMPERATURES ARE FORECAST FOR
PARTS OF THE SOUTHEAST REGION. THE HIGHEST PROBABILITIES FOR ABOVE NORMAL
TEMPERATURES OVER THE CONUS EXCEED 50 PERCENT FOR MUCH OF THE SOUTHWEST AND THE
NORTHEAST. PROBABILITIES GREATER THAN 70 PERCENT FOR ABOVE NORMAL TEMPERATURES
ARE INDICATED FOR NORTHWESTERN ALASKA. THE SON 2018 PRECIPITATION OUTLOOK
INDICATES ENHANCED PROBABILITIES FOR ABOVE NORMAL PRECIPITATION FOR COASTAL
STATES OF THE SOUTHEAST, AS WELL AS OVER THE AREA EXTENDING FROM SOUTHERN
CALIFORNIA AND THE DESERT SOUTHWEST INTO THE GREAT BASIN AND CENTRAL ROCKIES.
INCREASED CHANCES FOR ABOVE NORMAL PRECIPITATION ARE ALSO FORECAST ACROSS
MAINLAND ALASKA. BELOW NORMAL PRECIPITATION IS MORE LIKELY FOR MUCH OF THE
PACIFIC NORTHWEST.

DURING THE AUTUMN AND WINTER 2018-19, THE TEMPERATURE AND PRECIPITATION
OUTLOOKS ARE CONSISTENT WITH THE ELEVATED PROBABILITY OF EL NINO DEVELOPMENT
AND ITS IMPACTS, WITH ADJUSTMENTS RELATED TO MODEL FORECASTS AND DECADAL
TIMESCALE CLIMATE TRENDS. TEMPERATURE OUTLOOKS FOR WINTER 2018-2019 WERE
MODIFIED OVER PARTS OF THE CENTRAL PLAINS AND SOUTHWEST REGIONS TO REPRESENT
THE MODERATION OF PROBABILITIES FOR ABOVE NORMAL TEMPERATURES BY A POTENTIAL
SHIFT OF THE JET STREAM AND STORM TRACKS SOUTHWARD, DUE TO THE IMPACTS OF A
POTENTIAL EL NINO. PRECIPITATION OUTLOOKS FOR WINTER 2018-2019 WERE MODIFIED TO
REMOVE ABOVE NORMAL PRECIPITATION AREAS FROM THE CENTRAL PLAINS, WHERE THE
SIGNAL DUE TO EL NINO IS WEAK. AREAS OF PROBABLE ABOVE NORMAL PRECIPITATION IN
LATE WINTER 2018-2019 AND EARLY SPRING 2019 OUTLOOKS WERE EXPANDED WESTWARD
INTO SOUTHERN CALIFORNIA, REPRESENTING IMPACTS OF THE POTENTIAL SHIFT IN THE
STORM TRACK DUE TO EL NINO.

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

OCEANIC AND ATMOSPHERIC OBSERVATIONS ACROSS THE EQUATORIAL PACIFIC INDICATE
ENSO-NEUTRAL CONDITIONS HAVE PERSISTED INTO EARLY AUGUST. OBSERVED WEEKLY SSTS
INDICATE POSITIVE ANOMALIES OVER ALMOST THE ENTIRE EQUATORIAL PACIFIC OCEAN,
WITH ANOMALIES EXCEEDING 0.5 C GENERALLY WEST OF THE INTERNATIONAL DATE LINE.
POSITIVE SUBSURFACE TEMPERATURE ANOMALIES HAVE PERSISTED INTO EARLY AUGUST, AT
DEPTHS OF 50 TO 300 METERS FROM 130 E TO 130 W LONGITUDE AND NEAR THE SURFACE
IN THE EASTERN PACIFIC. PERSISTENT SUBSURFACE POSITIVE HEAT ANOMALIES
CONTRIBUTE TO THE CONTINUED LIKELIHOOD OF THE DEVELOPMENT OF EL NINO CONDITIONS
BY AUTUMN 2018.

OUTGOING LONGWAVE RADIATION (OLR) ANOMALIES INDICATED SUPPRESSED CONVECTION
OVER PARTS OF THE WESTERN MARITIME CONTINENT AND NEAR THE INTERNATIONAL DATE
LINE. LOW-LEVEL WINDS WERE NEAR AVERAGE OVER MOST OF THE EQUATORIAL PACIFIC,
WHILE UPPER-LEVEL WESTERLY WIND ANOMALIES WERE OBSERVED OVER THE EASTERN
TROPICAL PACIFIC OCEAN. OVERALL, ATMOSPHERIC CONDITIONS INDICATE THE
CONTINUATION OF ENSO-NEUTRAL CONDITIONS.


PROGNOSTIC DISCUSSION OF SST FORECASTS

THE CPC SST CONSOLIDATION (CON) FOR THE NINO 3.4 REGION PREDICTS THE LIKELIHOOD
OF TEMPERATURE ANOMALIES GREATER THAN POSITIVE 0.5 DEGREES C TO BE GREATER THAN
50 PERCENT BY ASO WITH POSITIVE ANOMALIES PEAKING AT ABOUT POSITIVE 1.0 DEGREES
C DURING NDJ 2018-19. THE SST CONSTRUCTED ANALOG, MARKOV MODEL, AND CFS
INDICATE PEAK ANOMALY VALUES GREATER THAN POSITIVE 1.0 DEGREES C THIS UPCOMING
WINTER. THE CPC/IRI CONSENSUS FORECAST FAVORS THE ONSET OF EL NINO DURING THE
NORTHERN HEMISPHERE AUTUMN WITH PROBABILITIES OF EL NINO AROUND 70 PERCENT
DURING NDJ AND DJF 2018-19.

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

THE CONTINUED LIKELIHOOD OF EL NINO DEVELOPMENT IS A LARGE FACTOR IN THE AUTUMN
2018 AND WINTER 2018-19 OUTLOOKS. TOOLS USED FOR THE SEASONAL OUTLOOKS INCLUDED
DYNAMICAL MODEL FORECAST GUIDANCE SUCH AS THE NORTH AMERICAN MULTI-MODEL
ENSEMBLE (NMME), AS WELL AS STATISTICAL GUIDANCE SUCH AS THE ENSO-OCN
REGRESSION FORECAST, THE SST-BASED CONSTRUCTED ANALOG, AND CANONICAL
CORRELATION ANALYSIS (CCA). A RELATIVELY NEW TOOL IN THE CPC SUITE IS THE CBAM,
OR CALIBRATION, BRIDGING, AND MERGING FORECAST TOOL. THIS USES A BAYESIAN
APPROACH TO THE NMME MODEL CALIBRATION AND CONSOLIDATION, AS WELL AS A HYBRID
STATISTICAL-DYNAMICAL FORECAST, IN WHICH NMME CONSTITUENT-MODEL NINO 3.4
FORECASTS ARE STATISTICALLY BRIDGED TO PREDICTED TEMPERATURE AND PRECIPITATION
USING A BAYESIAN MODEL. THE OUTLOOKS DURING THE 2019 WARM SEASON WERE BASED
PRIMARILY ON THE ENSO-OCN TOOL, WHICH INCORPORATES DECADAL CLIMATE TRENDS AND
ANY RESIDUAL IMPACTS OF ENSO VARIABILITY.

PROGNOSTIC DISCUSSION OF OUTLOOKS - SON 2018 TO SON 2019

TEMPERATURE

ABOVE NORMAL TEMPERATURES ARE LIKELY FOR MUCH OF THE CONUS AND ALASKA DURING
SON 2019 WITH THE HIGHEST PROBABILITIES OVER THE CONUS FORECAST FOR THE FOUR
CORNERS AND NORTHEAST REGIONS, BASED ON CALIBRATED NMME FORECASTS, USING
PROBABILITY ANOMALY CORRELATIONS, AND DECADAL CLIMATE WARMING. THE CBAM
FORECASTS INDICATE GREATER UNCERTAINTY AND WEAKER PROBABILITIES FOR AREAS OF
THE NORTHWEST CONUS THAN THE PREVIOUS OUTLOOK. PROBABILITIES OF ABOVE NORMAL
TEMPERATURES WERE ALSO DECREASED SLIGHTLY FOR PARTS OF THE SOUTHWEST IN THE DJF
AND JFM 2019 OUTLOOKS, BASED ON THE LATEST CALIBRATED NMME MODEL GUIDANCE.
EQUAL CHANCES FOR BELOW, NEAR, OR ABOVE NORMAL TEMPERATURES ARE FORECAST FOR
PARTS OF THE SOUTHEAST REGION FROM AUTUMN INTO WINTER OUTLOOKS, WHERE
TEMPERATURES ARE MODERATED BY THE POTENTIAL IMPACTS OF A DEVELOPING EL NINO,
AND UNCERTAINTY IS GREATEST.

THE ELEVATED CHANCES FOR EL NINO DEVELOPMENT WERE A FACTOR IN THE TEMPERATURE
OUTLOOKS, BEGINNING IN THE AUTUMN AND BECOMING MORE PROMINENT DURING THE WINTER
2018-19. BASED ON REGRESSIONS FROM THE CPC NINO 3.4 SST CONSOLIDATION
FORECASTS, PROBABILITIES FOR ABOVE NORMAL TEMPERATURES ARE GREATEST, EXCEEDING
50 PERCENT, FOR PARTS OF THE PACIFIC NORTHWEST AND OVER PARTS OF THE NORTHERN
PLAINS AND GREAT LAKES REGION, DURING WINTER SEASONS. AN EXPECTED LACK OF SEA
ICE ELEVATES CHANCES FOR ABOVE NORMAL TEMPERATURES FOR WESTERN AND NORTHERN
COASTAL AREAS OF ALASKA DURING THE AUTUMN SEASONAL OUTLOOKS. TEMPERATURE
OUTLOOKS AT LONGER LEAD TIMES, FOLLOWING THE FMA 2019 SEASON, INDICATE ELEVATED
PROBABILITIES OF ABOVE NORMAL TEMPERATURES FOR MOST OF THE FORECAST DOMAIN,
PRIMARILY BASED ON DECADAL CLIMATE TRENDS. CLIMATE TREND SIGNALS ARE WEAKEST
FOR PARTS OF THE NORTHERN CENTRAL CONUS FROM MJJ THROUGH ASO 2018, WHERE EQUAL
CHANCES OF BELOW, NEAR AND ABOVE NORMAL TEMPERATURES ARE INDICATED.

PRECIPITATION

THE PRECIPITATION OUTLOOKS ARE BASED PRIMARILY ON THE LATEST DYNAMICAL MODEL
GUIDANCE FROM THE NMME AND IMPACTS OF A POTENTIAL EL NINO, FOR SON 2018 THROUGH
MAM 2019. ABOVE NORMAL PRECIPITATION IS LIKELY FOR A LARGE AREA OF THE
SOUTHWEST CONUS IN THE SON 2018 OUTLOOK, EXTENDING NORTHWARD AS FAR AS SOUTHERN
IDAHO AND WYOMING, WITH THE PREDICTION OF AN ENHANCED MONSOON, AS WELL AS THE
POTENTIAL FOR MOISTURE SURGES FROM THE EASTERN TROPICAL PACIFIC, WHICH EXPANDS
THE AREA OF PROBABLE ABOVE NORMAL PRECIPITATION INTO SOUTHERN CALIFORNIA.
OUTLOOKS FOR OND 2018 THROUGH MAM 2019 RESEMBLE THE CANONICAL PATTERN OF EL
NINO IMPACTS, WITH ENHANCED CHANCES OF ABOVE NORMAL PRECIPITATION FOR PARTS OF
THE SOUTHERN CONUS, AND BELOW NORMAL PRECIPITATION LIKELY IN THE PACIFIC
NORTHWEST THROUGH DJF 2018-2019 AND FOR THE MIDWEST REGION LATER IN THE
UPCOMING WINTER. THE LATEST PRECIPITATION FORECASTS FROM THE NMME AND CBAM
INCREASE PROBABILITIES OF ABOVE NORMAL PRECIPITATION FOR PARTS OF THE SOUTHWEST
IN EARLY WINTER 2018-2019. PROBABILITIES OF ABOVE NORMAL PRECIPITATION ARE
ENHANCED FOR SOUTHERN ALASKA FROM SON 2018 THROUGH FMA 2019, AS INDICATED BY
TOOLS BASED ON THE IMPACTS OF EL NINO, SUCH AS THE ENSO-OCN AND BRIDGED
NMME-BASED CBAM FORECASTS. PROBABILITIES OF ABOVE NORMAL PRECIPITATION ARE
ENHANCED FOR OTHER AREAS OF ALASKA, INCLUDING WESTERN AND NORTHERN COASTAL
REGIONS, DUE TO POSITIVE DECADAL TRENDS IN PRECIPITATION RELATED TO POSITIVE
ATMOSPHERIC TEMPERATURE TRENDS AND REDUCED SEA ICE COVER.

THE PRECIPITATION OUTLOOKS FOR AMJ 2019 THROUGH SON 2019 ARE PRIMARILY BASED ON
DECADAL CLIMATE TRENDS. PRECIPITATION TRENDS ENHANCE THE CHANCES OF ABOVE
NORMAL PRECIPITATION FOR PARTS OF THE NORTHEAST CONUS FROM AMJ THROUGH SON
2019, AND ENHANCE THE CHANCES OF BELOW NORMAL PRECIPITATION FOR PARTS OF THE
NORTHWEST CONUS IN MJJ THROUGH ASO 2019.


FORECASTER: DAN COLLINS

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 20 2018


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

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