PROGNOSTIC DISCUSSION FOR LONG-LEAD SEASONAL OUTLOOKS NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD 830 AM EST THU DEC 15 2016 SUMMARY OF THE OUTLOOK FOR NON-TECHNICAL USERS WEAK LA NINA CONDITIONS CONTINUE ACROSS THE EQUATORIAL PACIFIC OCEAN, AS REPRESENTED IN CURRENT OCEANIC AND ATMOSPHERIC OBSERVATIONS. THE OFFICIAL CPC ENSO FORECAST INDICATES A TRANSITION TO ENSO-NEUTRAL CONDITIONS DURING JANUARY-MARCH 2017. ENSO-NEUTRAL CONDITIONS ARE FAVORED TO PERSIST THROUGH AT LEAST THE BOREAL SUMMER. THE JANUARY-FEBRUARY-MARCH (JFM) 2017 TEMPERATURE OUTLOOK FAVORS ABOVE-NORMAL TEMPERATURES ALONG THE EAST COAST AND ACROSS THE SOUTHERN TIER OF THE CONUS, WITH THE HIGHEST ODDS (GREATER THAN 50 PERCENT) FORECAST ACROSS PARTS OF NEW MEXICO AND TEXAS. ABOVE-NORMAL TEMPERATURES ARE ALSO FAVORED FOR WESTERN AND NORTHERN ALASKA. INCREASED CHANCES FOR BELOW-NORMAL TEMPERATURES DURING JFM ARE FORECAST FROM PARTS OF THE PACIFIC NORTHWEST EAST TO THE NORTHERN GREAT PLAINS AND UPPER MISSISSIPPI VALLEY. THE JFM 2017PRECIPITATION OUTLOOK INDICATES ENHANCED PROBABILITIES OF ABOVE-MEDIAN PRECIPITATION AMOUNTS FOR THE PACIFIC NORTHWEST ALONG WITH NORTHERN AREAS OF THE GREAT BASIN, ROCKIES, AND HIGH PLAINS. INCREASED CHANCES OF ABOVE MEDIAN-PRECIPITATION ARE ALSO FAVORED FROM THE GREAT LAKES SOUTH TO THE OHIO AND TENNESSEE VALLEYS ALONG WITH PARTS OF ALASKA. BELOW-MEDIAN PRECIPITATION AMOUNTS ARE MOST LIKELY FOR SOUTHERN CALIFORNIA, THE SOUTHWEST, SOUTHERN GREAT PLAINS, GULF COAST, FLORIDA, AND THE SOUTHERN ATLANTIC COASTAL AREAS. EQUAL CHANCES (EC) ARE FORECAST AMONG AREAS WHERE 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 INDICATE THAT LA NINA CONDITIONS ARE CURRENTLY PRESENT. DURING THE PAST FOUR WEEKS, EQUATORIAL SSTS REMAINED BELOW (ABOVE)-AVERAGE ACROSS THE CENTRAL AND EASTERN PACIFIC OCEAN (NEAR THE MARITIME CONTINENT). NEGATIVE ANOMALIES CONTINUE BE RELATIVELY SMALL FROM THE DATE LINE TO THE SOUTH AMERICAN COAST. NEGATIVE SUBSURFACE TEMPERATURE ANOMALIES HAVE PERSISTED SINCE APRIL ACROSS THE CENTRAL AND EASTERN PACIFIC. HOWEVER, THESE ANOMALIES WEAKENED DURING NOVEMBER. THE MOST RECENT ONI VALUE (SEPTEMBER - NOVEMBER 2016), BASED ON SST DEPARTURES FROM AVERAGE IN THE NINO 3.4 REGION, IS -0.8 DEGREES C. ENHANCED CONVECTION REMAINS CENTERED OVER THE MARITIME CONTINENT, WITH SUPPRESSED CONVECTION EXTENDING EASTWARD FROM 160E ACROSS MUCH OF THE EQUATORIAL PACIFIC. DURING THE PAST COUPLE OF MONTHS, SUBSEASONAL VARIABILITY HAS DISRUPTED THIS PATTERN AND LED TO PERIODIC DRYING ACROSS PARTS OF THE MARITIME CONTINENT AND EASTERN INDIAN OCEAN. TRADE WINDS AVERAGED NEAR NORMAL ACROSS THE CENTRAL AND EASTERN EQUATORIAL PACIFIC FROM NOVEMBER 10 TO DECEMBER 9, 2016. THE ATMOSPHERIC CIRCULATION DURING OCTOBER FORCED A DRAMATIC COOLING OVER THE NORTH-CENTRAL PACIFIC BASIN. AS OF EARLY DECEMBER, NEGATIVE ANOMALIES ARE NOW PRESENT OVER THE NORTH PACIFIC, CENTERED AT 40N-150W. POSITIVE SST ANOMALIES, ALBEIT WITH SMALLER MAGNITUDE, CONTINUE FROM THE COASTAL PACIFIC NORTHWEST NORTH TO THE ALASKA PANHANDLE. PROGNOSTIC DISCUSSION OF SST FORECASTS THE CPC SST CONSOLIDATION FORECAST, WHICH INCLUDES THREE STATISTICAL FORECASTS ALONG WITH THE CFS, PREDICTS A TRANSITION FROM LA NINA TO ENSO-NEUTRAL CONDITIONS DURING JFM AND FMA 2017 WITH ENSO-NEUTRAL CONDITIONS FAVORED THEREAFTER. THE NORTH AMERICAN MULTI MODEL ENSEMBLE (NMME) ENSEMBLE MEAN FORECAST FOR THE NINO-3.4 SST ANOMALY IS SLIGHTLY WARMER THAN LAST MONTH, WITH ENSO-NEUTRAL FAVORED EARLY IN OUTLOOK PERIOD. BASED ON THE LATEST OBSERVATIONAL AND MODEL FORECAST INDICATORS, THE OFFICIAL CPC/IRI ENSO OUTLOOK FAVORS ENSO-NEUTRAL CONDITIONS AT 55% DURING JFM 2017. PROGNOSTIC TOOLS USED FOR U.S. TEMPERATURE AND PRECIPITATION OUTLOOKS THE OUTLOOKS FOR JFM 2017 WERE BASED LARGELY ON DYNAMICAL MODEL GUIDANCE AND STATISTICAL TOOLS THAT INCLUDE A CONSTRUCTED ANALOG BASED ON GLOBAL SST ANOMALY PATTERNS AND CANONICAL CORRELATION ANALYSIS THAT USES THE EVOLUTION OF SST AND SEA-LEVEL PRESSURE AS PREDICTORS. LINGERING CLIMATE EFFECTS TYPICALLY ASSOCIATED WITH LA NINA DURING THE WINTER WERE ALSO USED IN CREATING THE OUTLOOKS FOR JFM 2017. DURING THE NEXT FOUR LEADS (FMA THROUGH MJJ 2017), THE PRIMARY FACTORS IN CREATING THE SUBSEQUENT OUTLOOKS WERE THE CALIBRATED PROBABILISTIC FORECASTS FROM THE NMME AND TRENDS. THE LATER OUTLOOKS THROUGH NEXT WINTER 2017-18 WERE BASED ON TRENDS AND THE CPC CONSOLIDATION FORECAST. PROGNOSTIC DISCUSSION OF OUTLOOKS - JFM 2017 TO JFM 2018 TEMPERATURE THE LARGEST CHANGE IN THE CALIBRATED PROBABILISTIC NMME FORECAST FROM ONE MONTH AGO IS A COLDER SOLUTION FOR THE NORTHWESTERN U.S. FOR JFM 2017. THEREFORE, BELOW-NORMAL TEMPERATURES ARE FAVORED FOR PARTS OF THE PACIFIC NORTHWEST AND NORTHERN ROCKIES ALBEIT WITH MODEST PROBABILITIES. THE TEMPERATURE OUTLOOK REMAINS UNCERTAIN ACROSS THE NORTHERN AND CENTRAL GREAT PLAINS, GREAT LAKES, AND MIDWEST. STATISTICAL METHODS OFFER A COLDER SOLUTION ACROSS THESE AREAS COMPARED TO THE VARIOUS DYNAMICAL MODELS. BELOW-NORMAL TEMPERATURES ARE SLIGHTLY FAVORED ACROSS THE NORTHERN GREAT PLAINS AND UPPER MISSISSIPPI VALLEY, BUT THE TEMPERED PROBABILITIES REFLECT THE CONTINUED UNCERTAINTY IN THE TEMPERATURE OUTLOOK FOR THIS REGION. INCREASED CHANCES OF ABOVE-NORMAL TEMPERATURES, FORECAST ACROSS THE SOUTHERN TIER OF THE CONUS, ARE BASED LARGELY ON A CONSENSUS AMONG THE TOOLS. THE HIGHEST ODDS FOR ABOVE-NORMAL TEMPERATURES (GREATER THAN 50 PERCENT) ARE FORECAST ACROSS THE SOUTHWEST DUE TO TRENDS AND GOOD AGREEMENT BETWEEN DYNAMICAL MODELS AND STATISTICAL TOOLS. SUBSEASONAL TROPICAL VARIABILITY SUCH AS THE MADDEN-JULIAN OSCILLATION, ESPECIALLY DURING JANUARY AND FEBRUARY WHEN VARIANCE IS HIGHEST, MAY PLAY A ROLE IN DETERMINING THE OBSERVED TEMPERATURE FIELD DURING JFM 2017 ACROSS THE CENTRAL AND EASTERN U.S. IF ENHANCED CONVECTION REMAINS CENTERED OVER THE MARITIME CONTINENT AND FAR WESTERN PACIFIC, THE COLDER OUTCOME INDICATED BY STATISTICAL GUIDANCE IS MORE LIKELY ACROSS THE NORTHERN CONUS. FOLLOWING A TWO MONTH PERIOD OF A NEGATIVE ARCTIC OSCILLATION (AO), THIS INDEX HAS RECENTLY BECOME POSITIVE DURING EARLY DECEMBER. THE GFS MODEL INDICATES THAT A POSITIVE AO INDEX WILL PERSIST INTO THE LATTER HALF OF DECEMBER. DUE TO POOR MODEL PERFORMANCE SINCE EARLY NOVEMBER WITH THE AO INDEX FORECAST, ITS STATUS IS UNCERTAIN ENTERING JANUARY 2017 AND ITS POTENTIAL INFLUENCE IS UNKNOWN AT THIS TIME. THE TEMPERATURE OUTLOOK FOR FMA 2017 IS VERY SIMILAR TO JFM WITH LITTLE CHANGES APPARENT AMONG THE DYNAMICAL AND STATISTICAL TOOLS. AS A SHIFT TO ENSO-NEUTRAL CONDITIONS IS LIKELY TO OCCUR DURING THE NEXT THREE MONTHS, THE TEMPERATURE OUTLOOKS FROM MAM THROUGH MJJ 2017 ARE BASED LARGELY ON THE CALIBRATED PROBABILISTIC FORECASTS FROM THE NMME ALONG WITH TRENDS. BEYOND MJJ 2017, NO CHANGES WERE MADE TO THE TEMPERATURE OUTLOOKS FROM THE PREVIOUS OUTLOOKS. DURING THE WINTER 2017-18, THE TEMPERATURE OUTLOOKS ARE BASED ON TRENDS. PRECIPITATION THE JFM 2017 PRECIPITATION OUTLOOK IS BASED ON THE CALIBRATED DYNAMICAL MODEL GUIDANCE FROM THE NMME AND IS CONSISTENT WITH LINGERING EFFECTS FROM THE CURRENT LA NINA EVENT. MODEST PROBABILITIES, SIMILAR TO THE TEMPERATURE OUTLOOK AT THIS EARLY LEAD, REFLECT CONTINUED UNCERTAINTY ON THE HOW MUCH INFLUENCE THE WEAKENING LA NINA HAS ON THE CLIMATE PATTERN ACROSS THE MIDDLE LATITUDES. COVERAGE OF FAVORED AREAS FOR ANOMALOUS PRECIPITATION DECREASE FROM FMA THROUGH AMJ 2017 AS FORECAST CONFIDENCE DIMINISHES WITH A WEAKENING SIGNAL AMONG PRECIPITATION TOOLS. DURING JJA AND JAS 2017, BELOW (ABOVE)-MEDIAN PRECIPITATION FAVORED FOR THE PACIFIC NORTHWEST (NEW ENGLAND) IS RELATED TO HISTORICAL TRENDS. BY NEXT WINTER 2017-18, INCREASED CHANCES OF BELOW-MEDIAN PRECIPITATION FORECAST ACROSS PARTS OF THE SOUTHEAST AND ALONG THE WEST COAST ARE ALSO BASED ON TRENDS. FORECASTER: BRAD PUGH 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 JAN 19 2017 1981-2010 BASE PERIOD MEANS WERE IMPLEMENTED EFFECTIVE WITH THE MAY 19, 2011 FORECAST RELEASE. $$