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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 Jun 2016


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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 19 2016

SUMMARY OF THE OUTLOOK FOR NON-TECHNICAL USERS

CURRENT OCEANIC AND ATMOSPHERIC CONDITIONS SUGGEST THAT A RAPID TRANSITION FROM
EL NINO CONDITIONS TO ENSO-NEUTRAL AND, EVENTUALLY, LA NINA CONDITIONS IS WELL
UNDERWAY. THE LATEST CPC/IRI CONSENSUS FORECAST INDICATES A 50% PROBABILITY OF
LA NINA FOR JJA, WITH PROBABILITIES INCREASING TO ABOUT 75% BY AUTUMN AND
WINTER.

THE JUNE-JULY-AUGUST (JJA) 2016 TEMPERATURE OUTLOOK INDICATES INCREASED
PROBABILITIES OF ABOVE-NORMAL TEMPERATURES ACROSS MUCH OF THE CONTINENTAL U.S.
AND ALASKA, WITH THE EXCEPTION OF PARTS OF THE CENTRAL U.S., WHERE THE FORECAST
DOES NOT DEVIATE FROM THE CLIMATOLOGICAL DISTRIBUTION. THE HIGHEST
PROBABILITIES FOR ABOVE-NORMAL TEMPERATURES ARE NEARER THE COASTS. THE JJA 2016
PRECIPITATION OUTLOOK FAVORS ABOVE-MEDIAN PRECIPITATION FOR PARTS OF THE
ROCKIES AND CENTRAL PLAINS, AS WELL AS PARTS OF NEW ENGLAND.

AT LONGER LEADS, THE FORECAST BEGINS TO MORE EXPLICITLY ACCOUNT FOR DEVELOPING
LA NINA CONDITIONS AND THE ASSOCIATED EXTRATROPICAL TELECONNECTIONS. BY WINTER,
BELOW-NORMAL TEMPERATURES ARE SLIGHTLY FAVORED FOR THE NORTH-CENTRAL U.S.,
WHILE ABOVE-NORMAL TEMPERATURES ARE FAVORED ACROSS THE SOUTHERN TIER OF THE
COUNTRY. BELOW-MEDIAN PRECIPITATION IS MORE LIKELY ACROSS THE SOUTHERN U.S. FOR
THE SAME LEAD.

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

EQUATORIAL PACIFIC SSTS GENERALLY REMAIN ABOVE CLIMATOLOGICAL MEANS, THOUGH THE
TRANSITION TO ENSO-NEUTRAL AND LA NINA CONDITIONS HAS BEGUN IN EARNEST. THE
LATEST ONI VALUE FOR FMA STANDS AT +1.6 C, BUT THE LATEST WEEKLY NINO 3.4 VALUE
HAS DROPPED TO +0.6 C. A NARROW REGION OF SLIGHTLY BELOW NORMAL TEMPERATURES
HAS EMERGED ALONG THE EQUATOR, AND ANOMALOUSLY COLD SUBSURFACE WATERS EXTEND
ACROSS MUCH OF THE BASIN. ANOMALOUS INTEGRATED (0-300 METERS DEPTH) EQUATORIAL
PACIFIC OCEAN HEAT CONTENT BECAME NEGATIVE IN MARCH AND CONTINUED TO DECREASE
THROUGH APRIL. THIS EXPANSE OF NEGATIVE HEAT CONTENT ANOMALIES CONTINUES TO
FAVOR A RAPID TRANSITION TO LA NINA CONDITIONS DURING 2016.

WITH RESPECT TO THE TROPICAL PACIFIC ATMOSPHERE, ENHANCED CONVECTION CONTINUED
FROM NEAR THE DATE LINE SOUTHEASTWARD ALONG THE SPCZ. TRADE WINDS HAVE BEEN
NEAR AVERAGE OVER THE PAST MONTH, WHILE THE CIRCULATION AT 200-HPA HAS REMAINED
MORE CONSISTENT WITH EL NINO, ALBEIT AT REDUCED AMPLITUDE.

THE EXTRATROPICAL PACIFIC OCEAN REMAINS CONSISTENT WITH THE POSITIVE PHASE OF
THE PACIFIC DECADAL OSCILLATION WITH ABOVE AVERAGE SSTS SOUTH OF ALASKA AND
ALONG THE WEST COAST. POSITIVE SST ANOMALIES IN THE WESTERN ATLANTIC NEAR THE
EAST COAST CONTINUE TO PERSIST AS WELL ESPECIALLY OFF THE NEW ENGLAND COAST.
ANOMALOUSLY COLD SSTS REMAIN IN THE NORTH ATLANTIC POLEWARD OF 50 N.

PROGNOSTIC DISCUSSION OF SST FORECASTS

THE CPC SST CONSOLIDATION CONTINUES TO FORECAST A RETURN TO ENSO-NEUTRAL
CONDITIONS BY MJJ AND WEAK LA NINA CONDITIONS BY SON. THE PEAK AMPLITUDE THIS
MONTH IS LOWER IN MAGNITUDE AT -0.68 C IN NDJ; THIS IS DUE TO THE CCA AND SST
CA STATISTICAL MODELS BACKING OFF ON THE STRENGTH OF THE FORECAST LA NINA.
PREDICTIONS FROM THE NORTH AMERICAN MULTI-MODEL ENSEMBLE (NMME) MEMBERS REMAIN
IN GOOD AGREEMENT, WITH THE ENSEMBLE MEAN AVERAGING NEAR -1.0 C FROM LATE
SUMMER THROUGH THE END OF THE YEAR.

THE CPC/IRI CONSENSUS FORECAST INDICATES THAT THE TRANSITION TO ENSO-NEUTRAL IS
MOST LIKELY BY EARLY SUMMER, AND THE PROBABILITY OF LA NINA DEVELOPING FIRST
EXCEEDS 50% IN JJA 2016, ONE MONTH EARLIER THAN IN THE PREVIOUS FORECAST. THE
PROBABILITY OF LA NINA PEAKS AT 76% FOR AUTUMN AND WINTER.

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

AS EL NINO CONTINUES TO WEAKEN, ENSO IMPACTS ARE NOT EXPLICITLY CONSIDERED FOR
JJA. HOWEVER, LAGGED IMPACTS FROM EL NINO ARE LIKELY TO REMAIN IMPLICITLY,
INCLUDING VIA THE EXTRATROPICAL SST FOOTPRINT LEFT IN ITS WAKE. SOIL MOISTURE
CONDITIONS WERE ALSO CONSIDERED IN EARLY OUTLOOKS WHERE SOME REGIONS CURRENTLY
HAVE SUBSTANTIAL DEPARTURES FROM NORMAL. PROSPECTS FOR A TRANSITION TO LA NINA
CONDITIONS WERE CONSIDERED PRIMARILY BEGINNING IN ASO 2016 AND THROUGHOUT THE
AUTUMN AND WINTER MONTHS AT THE CURRENT TIME. IN ADDITION TO THE ABOVE FACTORS,
CALIBRATED DYNAMICAL MODEL GUIDANCE FROM THE NMME, AND THE INTERNATIONAL
MULTI-MODEL ENSEMBLE (IMME) CONTRIBUTE TO THE OUTLOOKS THROUGH OND 2016. THE
OUTLOOKS ALSO UTILIZED QUITE HEAVILY THE SST-BASED CONSTRUCTED ANALOGUE AND
STATISTICAL GUIDANCE THAT COMBINES THE EFFECTS OF ENSO AND LINEAR TRENDS.

PROGNOSTIC DISCUSSION OF OUTLOOKS - JJA 2016 TO JJA 2017

TEMPERATURE

THE SUITE OF TEMPERATURE OUTLOOKS THIS MONTH ARE SIMILAR TO THOSE RELEASED LAST
MONTH AS THE GENERAL THINKING OVER THE OUTLOOK PERIOD REMAINS GENERALLY
UNCHANGED. WHAT FOLLOWS BELOW IS THE RATIONALE BEHIND THE CHANGES THAT WERE
MADE TO THE OUTLOOKS.

FOR JJA TEMPERATURE, CHANGES CONSISTED LARGELY OF INTRODUCING A REGION OF EQUAL
CHANCES ACROSS PARTS OF THE CENTRAL U.S. EAST OF THE ROCKIES. SUCH A CHANGE WAS
CONSISTENT WITH STATISTICAL GUIDANCE BASED ON TRENDS AND SOIL MOISTURE, AS WELL
AS STATISTICAL GUIDANCE FROM CURRENT TROPICAL AND EXTRATROPICAL SSTS. BEYOND
THAT, ABOVE-NORMAL TEMPERATURES ARE FAVORED COAST-TO-COAST, WITH LOWER
PROBABILITIES INDICATED IN THE CENTRAL CONUS. CARE WAS TAKEN TO MAKE SURE THE
TEMPERATURE FORECAST WAS CONSISTENT WITH THE FORECAST PRECIPITATION PATTERN
DURING THE WARM SEASON. THE CALIBRATED GUIDANCE FROM THE NMME WAS ALSO HEAVILY
UTILIZED HERE, ALTHOUGH THE FORECAST PATTERN IS LARGELY CONSISTENT WITH
OBSERVED TEMPERATURE TRENDS OVER THE PAST 65 YEARS.

A KEY UNCERTAINTY LINGERS WITH RESPECT TO THE ROLE OF LONG TERM TRENDS IN THE
WARM SEASON FORECASTS. SIMPLE PROJECTION OF THE CURRENT EXTRATROPICAL SST
PATTERN ONTO THE HISTORICAL TIME SERIES REVEALS THAT POSITIVE CORRELATIONS ARE
MORE LIKELY EARLY IN THE PERIOD, YIELDING SOMEWHAT OF AN ANTI-TREND SIGNAL. TO
BE SURE, THE LOW-FREQUENCY NEGATIVE SST ANOMALIES IN THE NORTH ATLANTIC COULD
BE RELATED TO CHANGING DECADAL VARIABILITY. SUCH VARIABILITY IS EASILY ALIASED
INTO TRENDS, AND ITS POSSIBLE THAT TRENDS ARE BEING SLIGHTLY OVER-UTILIZED AS A
RESULT. THIS BRIEF DISCUSSION IS JUST A SAMPLE OF THE THOUGHT PROCESS
UNDERPINNING THE APPLIED RESEARCH EFFORTS ON THIS ISSUE.

OTHER CHANGES WERE MADE TO THE FORECASTS CENTERED ON SON, WITH THE KEY CHANGES
BEING MADE TO SLOW THE TRANSITION TO A CANONICAL LA NINA RESPONSE. THIS CHANGE
IS BASED ON THE GOOD AGREEMENT BETWEEN CALIBRATED NMME PROBABILITIES AND
STATISTICAL GUIDANCE UTILIZING ENSO, TRENDS, AND GLOBAL SSTS.  BY WINTER,
SLIGHT CHANGES WERE MADE TO SHIFT THE CENTER OF THE ENHANCED PROBABILITIES FOR
BELOW-NORMAL TEMPERATURES SLIGHTLY EASTWARD, CONSISTENT WITH THE STATISTICAL
GUIDANCE AT THAT LEAD. THE LATEST CFS RUNS, INCIDENTALLY, SUPPORT THIS CHANGE.

PRECIPITATION

THE JJA 2016 PRECIPITATION OUTLOOK FAVORS ABOVE-MEDIAN PRECIPITATION FOR A
RELATIVELY SMALL REGION EXTENDING FROM THE NORTH-CENTRAL ROCKIES INTO THE
CENTRAL PLAINS. THE DYNAMICAL AND STATISTICAL GUIDANCE ARE IN REMARKABLY GOOD
AGREEMENT ON THIS FORECAST REGION. LONG TERM TRENDS FAVOR ABOVE-MEDIAN
PRECIPITATION ACROSS PARTS OF NEW ENGLAND. AN INCREASED CHANCE OF ABOVE-MEDIAN
PRECIPITATION IS ALSO FORECAST FOR WESTERN AND NORTHERN ALASKA FOR JJA AND JAS
2016 BY DYNAMICAL MODELS, RESULTING FROM ANOMALOUSLY OPEN SEA ICE AND
WARMER-THAN-AVERAGE OCEAN TEMPERATURES.

POTENTIAL LA NINA INFLUENCE AND STATISTICAL FORECAST GUIDANCE SUPPORT A SLIGHT
TILT IN THE ODDS TO ABOVE-MEDIAN SEASONAL TOTAL PRECIPITATION AMOUNTS FOR
COASTAL AREAS OF THE SOUTHEAST DURING JAS AND ASO 2016. BY SON, THE PATTERN
QUICKLY BEGINS TO TRANSITION TOWARD DRIER-THAN-NORMAL CONDITIONS OVER THE
SOUTHEAST AS THE MIDLATITUDE LA NINA TELECONNECTION INTENSIFIES. POTENTIAL LA
NINA CONDITIONS ALSO SUPPORT FAVORED BELOW-MEDIAN PRECIPITATION ACROSS PORTIONS
OF CENTRAL PLAINS WESTWARD TO THE CENTRAL ROCKIES DURING ASO 2016.

DURING AUTUMN OF 2016 AND WINTER OF 2016-17, THE POTENTIAL FOR ONGOING LA NINA
CONDITIONS IS THE PRIMARY FACTOR FOR INCREASED PROBABILITIES OF BELOW-MEDIAN
PRECIPITATION ACROSS THE SOUTHERN TIER OF THE CONTIGUOUS U.S. AND THE SOUTHERN
COAST OF ALASKA, AND INCREASED PROBABILITIES OF ABOVE-MEDIAN PRECIPITATION FOR
THE PACIFIC NORTHWEST AND OHIO VALLEY AND CENTRAL GREAT LAKES. THIS FORECAST
PROBABILITIES ARE UNCHANGED FROM THE LAST FORECAST CYCLE, SINCE THE ENSO
FORECAST REMAINS STABLE.

AT THE LONGEST LEADS, MJJ AND JJA 2017, A SLIGHT TILT TOWARD ABOVE-MEDIAN
PRECIPITATION FOR NEW ENGLAND WAS ADDED DUE TO STRONG LONG TERM TRENDS.

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/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 JUN 16 2016


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

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