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. $$