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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 ASO 2017
    1.5mn SON 2017
    2.5mn OND 2017
    3.5mn NDJ 2017
    4.5mn DJF 2017
    5.5mn JFM 2018
    6.5mn FMA 2018
    7.5mn MAM 2018
    8.5mn AMJ 2018
    9.5mn MJJ 2018
   10.5mn JJA 2018
   11.5mn JAS 2018
   12.5mn ASO 2018
    0.5mn Aug 2017


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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 JUL 20 2017

SUMMARY OF THE OUTLOOK FOR NON-TECHNICAL USERS

THE AUGUST-SEPTEMBER-OCTOBER (ASO) 2017 TEMPERATURE OUTLOOK INDICATES INCREASED
CHANCES OF ABOVE-NORMAL TEMPERATURES ACROSS ALASKA AND THE CONTIGUOUS U.S.,
ALTHOUGH PROBABILITIES ARE REDUCED FROM PARTS OF THE SOUTHERN PLAINS TO THE
CENTRAL MISSISSIPPI VALLEY. THE HIGHEST PROBABILITIES FOR ABOVE-NORMAL
TEMPERATURES ARE FORECAST FOR PARTS OF THE NORTHERN ROCKIES AND INTERMOUNTAIN
WEST, THE GULF COAST AND ATLANTIC COASTS, THE NORTHEAST, AND WESTERN AREAS OF
ALASKA. THE ASO 2017 PRECIPITATION OUTLOOK INDICATES AN INCREASED CHANCE FOR
ABOVE-MEDIAN PRECIPITATION FOR PARTS OF THE SOUTHERN PLAINS, THE SOUTHWEST,
SOUTHWESTERN ALASKA, AND THE ALEUTIAN ISLANDS.

DURING THE AUTUMN AND WINTER 2017-18, THE CHANCES OF EL NINO DEVELOPMENT ARE
LOWER COMPARED TO LAST MONTH. SINCE ENSO-NEUTRAL CONDITIONS ARE MOST LIKELY TO
PERSIST, THE TEMPERATURE AND PRECIPITATION OUTLOOKS DURING THE COLD SEASON ARE
BASED PRIMARILY ON DYNAMICAL MODEL GUIDANCE AND DECADAL TRENDS.

EQUAL CHANCES (EC) ARE FORECAST OVER AREAS WHERE PROBABILITIES OF ABOVE-,
BELOW-, OR NEAR-NORMAL SEASONAL MEAN TEMPERATURES AND 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. WHILE SEA SURFACE TEMPERATURES (SSTS) ARE SLIGHTLY
ABOVE AVERAGE IN THE EAST-CENTRAL PACIFIC OCEAN, ATMOSPHERIC CONDITIONS ARE
REPRESENTATIVE OF ENSO-NEUTRAL CONDITIONS. THE OBSERVED WEEKLY SSTS CENTERED ON
JULY 12 INDICATE POSITIVE SST ANOMALIES OF 0.5 TO 1 DEGREE C JUST TO THE WEST
OF THE DATE LINE AND FROM ABOUT 170W TO 120W LONGITUDE ALONG THE EQUATOR. THE
UPPER-OCEAN TEMPERATURE ANOMALY IS ABOVE AVERAGE ACROSS MUCH OF THE EQUATORIAL
PACIFIC OCEAN TO A DEPTH OF 100 TO 150 METERS, THOUGH WITH WEAK ANOMALIES OF
LESS THAN 2 DEGREES C.

DESPITE WARMER-THAN-AVERAGE OCEAN TEMPERATURES ACROSS THE CENTRAL AND EASTERN
PACIFIC SINCE MARCH, ATMOSPHERIC CONVECTIVE ANOMALIES FROM JUNE 17 TO JULY 12
CONTINUE TO REMAIN NEAR AVERAGE FROM NEAR THE DATE LINE TO THE EASTERN TROPICAL
PACIFIC. ENHANCED CONVECTION WAS OBSERVED ACROSS PARTS OF INDONESIA DURING THIS
TIME PERIOD. WESTERLY ANOMALIES IN LOWER LEVEL WINDS AT 850-HPA WERE OBSERVED
OVER THE EAST-CENTRAL TROPICAL PACIFIC, WHILE EASTERLY ANOMALIES WERE OBSERVED
IN UPPER LEVEL 200-HPA WINDS OVER THE EASTERN PACIFIC. THESE ATMOSPHERIC
INDICATORS ARE CONSISTENT WITH ENSO-NEUTRAL CONDITIONS.

PROGNOSTIC DISCUSSION OF SST FORECASTS

MOST MODELS OF THE NORTH AMERICAN MULTI-MODEL ENSEMBLE (NMME) INDICATE A
CONTINUATION OF ENSO-NEUTRAL CONDITIONS THROUGH THE AUTUMN, WITH SOME MODELS
INDICATING WEAK TO MODERATE EL NINO CONDITIONS. THE NCEP CFSV2 PREDICTS
NEAR-ZERO TEMPERATURE ANOMALIES IN THE EAST-CENTRAL TROPICAL PACIFIC OCEAN BY
THE BEGINNING OF AUTUMN. THE CPC NINO 3.4 SST CONSOLIDATION OF THE CFS AND
STATISTICAL FORECASTS INDICATES ELEVATED PROBABILITIES OF POSITIVE TEMPERATURE
ANOMALIES THROUGH SON, AND A TEMPERATURE ANOMALY CLOSE TO ZERO DEGREES IS MOST
LIKELY BY OND. THE CPC/IRI CONSENSUS FORECAST INDICATES PERSISTENCE OF
ENSO-NEUTRAL CONDITIONS IS MOST LIKELY THROUGH FMA 2018 WITH A PROBABILITY
GREATER THAN 50%, WHILE THE PROBABILITY OF DEVELOPMENT OF EL NINO CONDITIONS
REMAINS ELEVATED FROM CLIMATOLOGICAL PROBABILITIES AND IS AT OR ABOVE 35%
THROUGH OND.

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

DYNAMICAL MODELS PROVIDE THE PRIMARY GUIDANCE FOR THE SEASONAL OUTLOOKS THROUGH
DJF 2017-2018, WITH DECADAL TEMPERATURE AND PRECIPITATION TRENDS PROVIDING THE
PRIMARY GUIDANCE FOR LONGER LEADS. THE CALIBRATED PROBABILITY FORECASTS FROM
THE NORTH AMERICAN MULTI-MODEL ENSEMBLE (NMME) AND ANOMALY FORECASTS FROM ITS
INDIVIDUAL MODELS, INCLUDING THE NCEP CFS, WERE USED THROUGH DJF 2017/2018. THE
DECREASING LIKELIHOOD OF EL NINO DEVELOPMENT, COMPARED TO PREVIOUS OUTLOOKS LED
TO ADJUSTMENTS IN THE OUTLOOKS, ESPECIALLY FOR THE WINTER SEASONS.

PROGNOSTIC DISCUSSION OF OUTLOOKS - ASO 2017 TO ASO 2018

TEMPERATURE

ABOVE-NORMAL TEMPERATURES ARE FAVORED ACROSS ALL OF THE FORECAST DOMAIN FOR THE
ASO OUTLOOK, AS WELL AS OUTLOOKS FOR SON 2017 THROUGH NDJ 2017-2018, AS
INDICATED BY A CONSENSUS OF MODELS FROM THE NMME, DRIVEN SOMEWHAT BY DECADAL
TEMPERATURE TRENDS. LOWER PROBABILITIES FOR ABOVE NORMAL TEMPERATURES ARE
INDICATED FOR ASO AND SON FROM PARTS OF TEXAS AND THE SOUTHERN PLAINS TO THE
CENTRAL MISSISSIPPI VALLEY, DUE TO POTENTIAL MODERATION OF TEMPERATURES BY
INCREASED SOIL MOISTURE IN RESPONSE TO PREDICTED PRECIPITATION IN THIS REGION.
THE HIGHEST PROBABILITIES OF ABOVE NORMAL TEMPERATURES IN ASO ARE INDICATED FOR
PARTS OF THE NORTHERN ROCKIES AND INTERMOUNTAIN WEST, AS WELL AS ALONG THE GULF
AND ATLANTIC COASTS, AND THE NORTHEAST, WHERE DECADAL TRENDS ARE GREATER IN
COMPARISON TO SEASONAL VARIABILITY. PROBABILITIES IN THE SOUTHWEST, WHERE
DECADAL TRENDS ARE ALSO LARGE, ARE MODERATED BY A FORECAST FOR ABOVE MEDIAN
PRECIPITATION AND RESULTING SURFACE-ATMOSPHERIC FEEDBACKS. PROBABILITIES FOR
ABOVE-NORMAL TEMPERATURES ARE ALSO HIGHEST FOR PARTS OF SOUTHWESTERN, WESTERN
AND NORTHWESTERN ALASKA, AS INDICATED BY THE PROBABILITY FORECASTS OF THE NMME,
LARGELY RESULTING FROM DECADAL TRENDS.

WITH ENSO-NEUTRAL CONDITIONS MOST LIKELY THROUGH WINTER, THE TEMPERATURE
OUTLOOKS FROM ASO 2017 TO DJF 2017-18 ARE BASED PRIMARILY ON THE NMME
CALIBRATED PROBABILITY FORECASTS. AN EXPECTED LACK OF SEA ICE ELEVATES CHANCES
FOR ABOVE-NORMAL TEMPERATURES ACROSS NORTHERN ALASKA DURING THE AUTUMN. DECADAL
TRENDS ARE USED AS GUIDANCE FOR THE TEMPERATURE OUTLOOKS AT LONGER LEADS FROM
MAM TO ASO 2018 AND INDICATE INCREASED PROBABILITIES OF ABOVE-NORMAL
TEMPERATURES WHERE TRENDS ARE THE LARGEST RELATIVE TO SEASONAL TEMPERATURE
VARIABILITY.

PRECIPITATION

ENHANCED PROBABILITIES FOR ABOVE MEDIAN PRECIPITATION FOR THE NORTHERN PLAINS
DURING THE FIRST SEVERAL LEADS IN LAST MONTHS OUTLOOKS HAVE BEEN REMOVED FROM
THE CURRENT OUTLOOKS, WHERE EQUAL CHANCES IS NOW INDICATED. THIS CHANGE IS
BASED ON THE MOST RECENT DYNAMICAL MODEL GUIDANCE FROM THE NMME AND CFS.
CALIBRATED PRECIPITATION PROBABILITY FORECASTS FROM THE NMME INDICATE ABOVE
MEDIAN PRECIPITATION IS MOST LIKELY FOR PARTS OF TEXAS AND THE SOUTHERN PLAINS
EXTENDING EASTWARD TO THE MISSISSIPPI RIVER. THIS SIGNAL CONTINUES IN THE
OUTLOOKS FOR SON 2017 THROUGH DJF 2017-2018. A CONSENSUS OF THE DYNAMICAL
MODELS INDICATE AN INCREASED CHANCE OF BELOW MEDIAN PRECIPITATION FOR PARTS OF
PACIFIC NORTHWEST FOR ASO. THE AUGUST PRECIPITATION FORECASTS FROM THE MOST
RECENT RUNS OF THE CFS AND ADDITIONAL DYNAMICAL MODEL FORECASTS FOR THE
BEGINNING OF AUGUST CONSISTENTLY INDICATE ABOVE MEDIAN PRECIPITATION FOR AUGUST
IN THE SOUTHWEST MONSOON REGION. AS THE MONTH OF AUGUST HAS GREATER
PRECIPITATION IN THIS REGION THAN THE FOLLOWING MONTHS, ENHANCED PRECIPITATION
IN AUGUST HAS AN INCREASED IMPACT ON THE TOTAL SEASONAL PRECIPITATION. ABOVE
MEDIAN PRECIPITATION IS THEREFORE INDICATED FOR THE SOUTHWEST FOR ASO. ABOVE
MEDIAN PRECIPITATION IS INDICATED FOR PARTS OF SOUTHERN ALASKA IN ASO 2017
THROUGH DJF 2017-2018, AS INDICATED BY CALIBRATED PRECIPITATION PROBABILITY
FORECASTS FROM THE NMME. DUE TO DECADAL TRENDS, ABOVE MEDIAN PRECIPITATION IS
MOST LIKELY FOR PARTS OF THE NORTHERN PLAINS AND GREAT LAKES REGION FROM MAM TO
MJJ 2018, AND FOR PARTS OF THE NORTHEAST FROM MJJ THROUGH ASO 2018.

SINCE THE PREVIOUS OUTLOOK, THE CHANCES FOR EL NINO DEVELOPMENT DURING THE
AUTUMN AND WINTER HAVE DECREASED. GIVEN THE LATEST ENSO FORECAST INDICATING A
GREATER CHANCE OF ENSO-NEUTRAL CONDITIONS THROUGH THE WINTER, THE INCREASED
CHANCES FOR BELOW MEDIAN PRECIPITATION FOR PARTS OF THE NORTHERN ROCKIES IN NDJ
AND DJF 2017-2018 HAVE BEEN REMOVED. PRECIPITATION OUTLOOKS FROM JFM THROUGH
FMA 2018 ARE BASED ON THE SEASONAL PRECIPITATION CONSOLIDATION FORECAST AND
DECADAL TRENDS.

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 AUG 17 2017


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

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