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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 JJA 2017
    1.5mn JAS 2017
    2.5mn ASO 2017
    3.5mn SON 2017
    4.5mn OND 2017
    5.5mn NDJ 2017
    6.5mn DJF 2017
    7.5mn JFM 2018
    8.5mn FMA 2018
    9.5mn MAM 2018
   10.5mn AMJ 2018
   11.5mn MJJ 2018
   12.5mn JJA 2018
    0.5mn Jun 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 MAY 18 2017

SUMMARY OF THE OUTLOOK FOR NON-TECHNICAL USERS

THE JUNE-JULY-AUGUST (JJA) 2017 TEMPERATURE OUTLOOK FAVORS ABOVE-NORMAL
TEMPERATURES FOR MUCH OF THE FORECAST DOMAIN. FOR THE CONTIGUOUS U.S.,
ABOVE-NORMAL SEASONAL MEAN TEMPERATURES ARE MOST LIKELY FOR THE EASTERN U.S.,
ACROSS THE SOUTHERN STATES, AND WEST OF ROCKY MOUNTAINS. THE GREATEST ODDS ARE
INDICATED FOR PARTS OF THE SOUTHWEST, THE GULF COAST AND ATLANTIC COASTAL
REGIONS. ABOVE-NORMAL TEMPERATURES ARE ALSO FAVORED FOR MUCH OF ALASKA.

THE JJA 2017 PRECIPITATION OUTLOOK INDICATES ENHANCED PROBABILITIES OF
ABOVE-MEDIAN PRECIPITATION FOR PARTS OF THE ROCKIES AND HIGH PLAINS, CENTERED
EAST OF THE CONTINENTAL DIVIDE, EXTENDING SOUTHWARD THROUGH THE SOUTHERN
PLAINS. ABOVE-MEDIAN PRECIPITATION IS ALSO SLIGHTLY FAVORED FOR PARTS OF
MAINLAND ALASKA.

AS THE FORECAST PROGRESSES TOWARD THE COLD SEASON, A SLIGHT TILT TOWARD EL NINO
(RELATIVE TO LA NINA) IS INDICATED BY THE LATEST OBJECTIVE GUIDANCE AND EXPERT
ASSESSMENTS. THIS HAS A SMALL IMPACT ON THE TEMPERATURE AND PRECIPITATION
FORECASTS FOR THE SEASONS SPANNING SON 2017 THROUGH FMA 2018.

EQUAL CHANCES (EC) ARE FORECAST OVER AREAS WHERE ODDS 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 AS A WHOLE
INDICATE ENSO-NEUTRAL CONDITIONS ARE CONTINUING. THE LATEST WEEKLY SST ANOMALY
MAP INDICATES THAT WEAKLY POSITIVE SST ANOMALIES EXIST ACROSS NEARLY THE ENTIRE
EQUATORIAL PACIFIC BASIN, WITH HIGHER AMPLITUDE ANOMALIES LOCATED NEAR THE
SOUTH AMERICAN COAST. THE HEAT CONTENT ANOMALY OF THE UPPER-OCEAN LAYERS, TO A
DEPTH OF 300 METERS, SUMMED ACROSS THE BASIN FROM THE DATE LINE TO 100W HAS
REBOUNDED FROM THE DECREASE OBSERVED LAST MONTH AND IS NOW POSITIVE.

IN THE ATMOSPHERE OVER THE PAST MONTH, LOWER TROPOSPHERIC ZONAL WIND ANOMALIES
WERE WEAK. OVER THE SAME PERIOD, MEASUREMENTS OF TROPICAL CONVECTION INDICATED
THE DEVELOPMENT OF ENHANCED CONVECTION JUST SOUTH OF THE EQUATOR WITH WEAKLY
ENHANCED CONVECTION CONTINUING OVER THE MARITIME CONTINENT. THIS COMBINATION OF
THE ATMOSPHERIC AND OCEANIC EVOLUTION SUGGESTS A SHIFT FURTHER AWAY FROM THE
REMNANT LA NINA BASE STATE.

PROGNOSTIC DISCUSSION OF SST FORECASTS

THE CPC NINO 3.4 SST INDEX CONSOLIDATION FORECAST, WHICH INCLUDES CANONICAL
CORRELATION ANALYSIS (CCA), CONSTRUCTED ANALOG (CA), AND MARKOV STATISTICAL
FORECASTS, ALONG WITH THE CFS DYNAMICAL MODEL, PREDICTS A MEDIAN TEMPERATURE
ANOMALY OF BETWEEN +0.4C AND +0.5C FOR THE COMING SEASONS FROM APPROXIMATELY
JJA THROUGH NDJ 2017, WITH EL NINO AS MOST LIKELY FROM LATE SUMMER THROUGH
AUTUMN. THE CFS HAS BACKED OFF ITS EL NINO FORECAST IN A FAIRLY DRAMATIC
FASHION OVER THE PAST MONTH, WHILE THE CA STATISTICAL FORECAST HAS BECOME THE
WARMEST CONSTITUENT MEMBER OF THE CONSOLIDATION FORECAST. THE LATEST FORECASTS
FROM THE DYNAMICAL SUITE OF MODELS FROM THE NMME CONTINUE TO FAVOR EL NINO
DEVELOPMENT, THOUGH NOT AS STRONGLY AS LAST MONTH. THE LATEST OFFICIAL ENSO
OUTLOOK FROM CPC/IRI PLACES THE ODDS OF EL NINO AND ENSO NEUTRAL AT ROUGHLY 45%
FROM JJA THROUGH DJF. THE CONSENSUS FORECAST INDICATES THE LIKELIHOOD OF A
REPEAT LA NINA EVENT TO BE SMALL DURING THIS FORECAST PERIOD.

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

THE PRIMARY TOOLS USED FOR THIS SET OF SEASONAL OUTLOOKS INCLUDED BOTH
STATISTICAL AND DYNAMICAL MODEL FORECAST GUIDANCE, AND IN PARTICULAR AT LONGER
LEADS, DECADAL TEMPERATURE AND PRECIPITATION TRENDS. THE CALIBRATED DYNAMICAL
MODEL GUIDANCE FROM THE NORTH AMERICAN MULTI-MODEL ENSEMBLE (NMME) AND, TO
LESSER EXTENT, ITS INDIVIDUAL MODELS, INCLUDING THE NCEP CFS, WERE IMPORTANT
CONTRIBUTORS TO THE OUTLOOKS THROUGH OND 2017. ANTECEDENT SOIL MOISTURE AND
SNOWPACK ANOMALIES IN CERTAIN REGIONS ALSO IMPACTED THE OUTLOOKS AT EARLY
LEADS. WHILE THE ENSO FORECAST REMAINS HIGHLY UNCERTAIN, THE SLIGHT TILT TOWARD
EL NINO WAS CONSIDERED IN THE TEMPERATURE AND PRECIPITATION FROM SON THROUGH
FMA.

PROGNOSTIC DISCUSSION OF OUTLOOKS - JJA 2017 TO JJA 2018

TEMPERATURE

THE LATEST JJA AND JAS 2017 TEMPERATURE OUTLOOKS INDICATE ABOVE-NORMAL
TEMPERATURES ARE MOST LIKELY FOR MUCH OF THE FORECAST DOMAIN, WITH THE
EXCEPTION OF PARTS ROCKIES AND PLAINS. THE CHANCES OF ABOVE-NORMAL SEASONAL
MEAN TEMPERATURES ARE SLIGHTLY ENHANCED FOR MUCH OF THE PACIFIC NORTHWEST, BUT
THE PROBABILITY OF ABOVE-NORMAL TEMPERATURES IS MODERATED BY RECENT POSITIVE
SNOW AND SOIL MOISTURE ANOMALIES. ABOVE-NORMAL TEMPERATURES ARE PARTICULARLY
ENHANCED FOR A REGION STRETCHING FROM THE SOUTHWEST, EASTWARD ACROSS THE FAR
SOUTHERN TIER OF THE CONUS INTO THE EASTERN U.S. THE GREATEST PROBABILITIES
EXCEED 50% FOR PARTS OF THE SOUTHWEST AND ALONG THE GULF AND ATLANTIC COASTS,
FOLLOWING THE CALIBRATED PROBABILISTIC GUIDANCE FROM THE NMME. NEGATIVE SOIL
MOISTURE ANOMALIES IN THE SOUTHEAST REGION ALSO CONTRIBUTE TO THE LIKELIHOOD OF
ANOMALOUS WARMTH. DECADAL CLIMATE TRENDS ALSO SUPPORT THE OUTLOOK AND ARE A
COMPONENT OF THE DYNAMICAL MODEL GUIDANCE. THESE FORECAST TOOLS ALSO SUPPORT
ENHANCED PROBABILITIES OF ABOVE-NORMAL TEMPERATURES FOR ALASKA.

POSITIVE SOIL MOISTURE ANOMALIES, COMBINED WITH PROBABILITIES FAVORING
ABOVE-MEDIAN PRECIPITATION, SUPPORT SOME EXPANION OF THE RELATIVE TEMPERATURE
WEAKNESS OVER PARTS OF THE ROCKIES AND PLAINS STATES FOR JJA AND JAS.
ADDITIONALLY, ANTECEDENT TROPICAL AND EXTRATROPICAL SST BOUNDARY CONDITIONS MAY
INDICATE SOME COMPONENT OF INTERANNUAL VARIABILITY THAT COULD DESTRUCTIVELY
INTERFERE WITH LONGER TERM WARMING TRENDS OVER PARTS OF THE CENTRAL AND EASTERN
CONUS. WHILE THE FORECAST STILL BROADLY FAVORS ABOVE-NORMAL TEMPERATURES, THE
PROBABILITIES ARE NOT EXCEPTIONAL, AND INDEED THE NMME FORECAST AND THE
OFFICIAL FORECAST SUGGEST A SLIGHTLY COOLER FORECAST FOR THE CONUS AS A WHOLE
THAN THAT ISSUED FOR LAST SUMMER FOR JJA AND JAS.


SUBTLE CHANGES WERE MADE TO LATER LEADS, FROM ASO TO FMA, BASED ON THE LATEST
MODEL GUIDANCE AND STATISTICAL FORECASTS THAT EMPHASIZE A SLIGHT TILT TOWARD EL
NINO IMPACTS. GENERALLY THIS IS SEEN AS A SLIGHT INCREASE IN PROBABILITIES
FAVORING ABOVE-NORMAL TEMPERATURE ACROSS THE NORTHERN TIER OF THE CONUS, AND A
REDUCTION OF THE SAME ACROSS THE FAR SOUTHERN TIER.

HIGH PROBABILITIES FOR ABOVE-NORMAL TEMPERATURES ARE INDICATED FOR THE NORTH
SLOPE OF ALASKA DURING SON AND OND 2017 DUE TO DECADAL TRENDS IN THE SEASONAL
CYCLE OF SEA ICE.

PRECIPITATION

FOR PRECIPITATION, THE JJA AND JAS 2017 OUTLOOKS INDICATE ABOVE-MEDIAN
PRECIPITATION FOR AREAS OF THE ROCKY MOUNTAINS AND TO THE EAST, INCLUDING PARTS
OF THE CENTRAL AND NORTHERN PLAINS. IN THE CASE OF JJA, A SLIGHT ENHANCEMENT OF
PROBABILITIES FAVORING ABOVE-MEDIAN TEMPERATURES EXTENDS SOUTHWARD THROUGH
TEXAS. FROM ASO THROUGH OND 2017, INCREASING CHANCES FOR EL NINO CONDITIONS AND
DYNAMICAL MODEL FORECASTS OF GREATER THAN AVERAGE SSTS IN THE EASTERN TROPICAL
PACIFIC LEAD TO A SOUTHWARD SHIFT OF THIS REGION OF LIKELY ABOVE-MEDIAN
PRECIPITATION INTO THE SOUTHWEST CONUS, EXTENDING ACROSS THE FAR SOUTHERN TIER
OF THE CONUS WITH STILL MODEST PROBABILITIES.

FOR LATE AUTUMN AND WINTER, FROM NDJ 2017-2018 THROUGH JFM 2018, THE LOW
PROBABILITY OF A LA NINA AND ELEVATED CHANCES FOR A POSSIBLE EL NINO NOW RESULT
IN THE INTRODUCTION OF PROBABILITIES ASSOCIATED WITH A CANONICAL EL NINO,
ALBEIT AT VERY LOW AMPLITUDE AND COVERAGE DUE TO THE HIGH UNCERTAINTY.
FOLLOWING JFM 2018, WEAK SIGNALS DUE TO DECADAL TRENDS IN PRECIPITATION ARE
INDICATED, INCLUDING BELOW-MEDIAN PRECIPITATION FOR PARTS OF THE SOUTHWEST
BEGINNING WITH THE MAM 2018 SEASON AND ABOVE-MEDIAN PRECIPITATION IN THE
NORTHERN-CENTRAL CONTIGUOUS U.S. BEGINNING WITH MAM 2018.

OVER ALASKA, CALIBRATED DYNAMICAL GUIDANCE FAVORS A SHIFT TOWARD ABOVE-MEDIAN
PRECIPITATION FOR PARTS OF THE MAINLAND DURING THE EARLY LEADS. DURING SON,
MODEST PROBABILITIES FAVORING ABOVE-MEDIAN PRECIPITATION ARE INTRODUCED OVER
SOUTHERN ALASKA TO ACCOUNT FOR THE TILT TOWARD EL NINO; THAT SIGNAL CONTINUES
IN THE FORECASTS THROUGH JFM 2018.

FORECASTER: STEPHEN BAXTER

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 JUN 15 2017


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

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