PROGNOSTIC DISCUSSION FOR LONG-LEAD SEASONAL OUTLOOKS NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD 830 AM EST THU NOV 17 2016 SUMMARY OF THE OUTLOOK FOR NON-TECHNICAL USERS CURRENT OCEANIC AND ATMOSPHERIC CONDITIONS OVER THE TROPICAL PACIFIC ARE CONSISTENT WITH A WEAK LA NINA EVENT. THE OFFICIAL CPC ENSO FORECAST INDICATES A 55% CHANCE OF LA NINA (ONI <= -0.5) CONTINUING THROUGH THE DJF WINTER SEASON. BEYOND THAT, ENSO NEUTRAL CONDITIONS ARE MOST LIKELY HEADING INTO BOREAL SUMMER, THOUGH THERE IS A SLIGHT TILT TOWARD EL NINO DEVELOPMENT RELATIVE TO CLIMATOLOGY. THE DJF 2016-2017 TEMPERATURE OUTLOOK INDICATES INCREASED PROBABILITIES OF ABOVE-NORMAL TEMPERATURES FOR MUCH OF THE SOUTHERN U.S., NEW ENGLAND, AND ALASKA. A SLIGHT TENDENCY TOWARD BELOW-NORMAL TEMPERATURES IS FORECAST OVER PARTS OF THE UPPER MIDWEST AND NORTHERN PLAINS. THIS OUTLOOK IS INFORMED MOSTLY BY OBJECTIVE EMPIRICAL GUIDANCE THAT INCORPORATES ENSO, TRENDS, AND OBSERVED SST EVOLUTION. CALIBRATED DYNAMICAL MODEL GUIDANCE IS ALSO CONSIDERED. THE DJF 2016-2017 PRECIPITATION OUTLOOK INDICATES INCREASED PROBABILITIES OF ABOVE-MEDIAN PRECIPITATION FOR PARTS OF THE NORTHERN TIER OF THE U.S., CENTERED ON THE NORTHERN ROCKIES AND GREAT LAKES. BELOW-MEDIAN PRECIPITATION IS FAVORED FOR MUCH OF THE SOUTHERN TIER OF THE CONTIGUOUS U.S. WITH THE GREATEST PROBABILITIES ALONG PARTS OF THE GULF COAST. THE OUTLOOK IS BASED ON A NUMBER OF FACTORS INCLUDING LA NINA CONSIDERATIONS AND SHORT TERM CLIMATE MODEL OUTPUT. 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 IN THE TROPICAL PACIFIC, BOTH OCEANIC AND ATMOSPHERIC OBSERVATIONAL INDICATORS (ON AVERAGE) INDICATE LA NINA CONDITIONS, THOUGH THE TRADE WINDS REMAIN NEAR NORMAL ON AVERAGE. SEA SURFACE TEMPERATURES (SSTS) ALONG THE EQUATOR IN THE PACIFIC BASIN REMAIN BELOW AVERAGE FROM 180W TO 100W, WHILE SSTS ARE ABOVE AVERAGE ACROSS THE FAR WESTERN PACIFIC AND IN A HORSESHOE PATTERN NORTH AND SOUTH OF THE AREA OF COOLER THAN NORMAL SSTS ALONG THE EQUATOR. IN THE NINO-3.4 REGION, THE MOST RECENT WEEKLY ANOMALY VALUE IS -0.7 DEGREES C WHILE THE MOST RECENT THREE-MONTH AVERAGE NINO-3.4 SST ANOMALY IS -0.7 DEGREES C FOR THE ASO SEASON. A RESERVOIR OF ANOMALOUSLY COOL SUBSURFACE WATERS CONTINUES AT DEPTH AND EXTENDS TO MORE THAN 150 METERS BELOW THE SURFACE, WITH THE LARGEST NEGATIVE ANOMALIES OF 2-4 DEGREES C BELOW AVERAGE FROM 100-150 METERS CENTERED NEAR 140W. OVER THE PAST SEVERAL WEEKS, ENHANCED CONVECTION HAS BEEN CENTERED OVER THE MARITIME CONTINENT, WITH SUPPRESSED CONVECTION EXTENDING EASTWARD FROM 160E ACROSS MUCH OF THE EQUATORIAL PACIFIC. RECENTLY, HOWEVER, SUBSEASONAL VARIABILITY HAS DISRUPTED THIS PATTERN AND LED TO DRYING ACROSS PARTS OF THE MARITIME CONTINENT AND EASTERN INDIAN OCEAN. TRADE WINDS OVER THE PAST MONTH HAVE BEEN NEAR AVERAGE. SSTS IN THE NORTHEAST PACIFIC AND ALONG THE COAST OF ALASKA REMAIN ABOVE AVERAGE, ALTHOUGH THE ATMOSPHERIC CIRCULATION HAS FORCED A DRAMATIC COOLING OVER THE NORTH-CENTRAL PACIFIC BASIN. POSITIVE SST ANOMALIES PERSIST IN THE WESTERN ATLANTIC NEAR THE U.S. EAST COAST, AND THE GULF OF MEXICO. PROGNOSTIC DISCUSSION OF SST FORECASTS THE CPC SST CONSOLIDATION FORECAST, WHICH INCLUDES THREE STATISTICAL FORECASTS ALONG WITH THE CFS, PREDICTS A WEAK LA NINA DURING DJF 2016-2017 WITH ENSO-NEUTRAL CONDITIONS FAVORED THEREAFTER. BY WINTER 2017-2018, THE CONSOLIDATION FAVORS LA NINA OVER EL NINO. 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 LA NINA CONDITIONS AT 55% DURING DJF 2016-2017, THE SAME PROBABILITY THAT WAS ISSUED LAST MONTH. PROGNOSTIC TOOLS USED FOR U.S. TEMPERATURE AND PRECIPITATION OUTLOOKS THE SUBSEQUENT TEMPERATURE AND PRECIPITATION OUTLOOKS CONSIDERED LA NINA REGRESSIONS, STATISTICAL TOOLS, SUCH AS REGRESSIONS BASED ON THE CPC CONSOLIDATED SST FORECAST, 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. ALSO CONSIDERED WERE THE CALIBRATED PROBABILISTIC FORECASTS FROM THE NMME, GUIDANCE FROM PARTICIPANT MODELS OF THE INTERNATIONAL MULTI-MODEL ENSEMBLE (IMME) AND THE CPC CONSOLIDATION (CPC CON) FORECAST. OTHER FACTORS INCLUDED POTENTIAL INFLUENCE FROM MORE LOCAL, COASTAL SSTS. PROGNOSTIC DISCUSSION OF OUTLOOKS - DJF 2016 TO DJF 2017 TEMPERATURE THE TEMPERATURE OUTLOOKS FOR DJF AND JFM REMAIN HIGHLY UNCERTAIN. STATISTICAL GUIDANCE USING SST-BASED PREDICTORS AND TRENDS HINT TOWARD A COLDER SOLUTION ACROSS THE NORTHERN CONUS, WHILE DYNAMICAL MODEL GUIDANCE IS NEARLY UNANIMOUS IN DEPICTING A WARMER-THAN-NORMAL SOLUTION OVER MOST OF NORTH AMERICA. HOWEVER, HINDCAST EVALUATION REVEALS THAT THE MODEL GUIDANCE HAS LIMITED FORECAST SKILL FOR THESE SEASONS, AND CALIBRATED GUIDANCE REVEALS SOME SIMILARITIES IN STRUCTURE TO THE STATISTICAL GUIDANCE. THE OFFICIAL OUTLOOK FAVORS THE STATISTICAL GUIDANCE, DEPICTING A TILT TOWARD BELOW-NORMAL TEMPERATURES OVER THE NORTHERN PLAINS AND UPPER MIDWEST. LA NINA REGRESSIONS WOULD TEND TO FAVOR A COLDER SOLUTION OVER THE NORTHWEST, BUT TRENDS AND BOTH STATISTICAL AND DYNAMICAL GUIDANCE ARE NOT SUPPORTIVE FOR DJF. BY JFM PROBABILITIES FAVORING BELOW-NORMAL TEMPERATURES ARE INTRODUCED. IT IS POSSIBLE THAT LOW-FREQUENCY EXTRATROPICAL VARIABILITY AND SUBSEASONAL TROPICAL VARIABILITY WILL BE PARTICULARLY IMPORTANT IN DETERMINING THE FINAL DISTRIBUTION OF TEMPERATURE ANOMALIES OVER NORTH AMERICA. THE ARCTIC OSCILLATION HAS BEEN IN A FAIRLY PERSISTENT NEGATIVE PHASE SINCE OCTOBER 1, AND IS FORECAST TO REMAIN GENERALLY NEGATIVE INTO DECEMBER. WHETHER THIS IS A HARBINGER OF THINGS TO COME THROUGHOUT THE WINTER SEASON IS NOT WELL KNOWN, BUT THERE IS SOME EVIDENCE TO SUGGEST AN NEGATIVE AO IS MORE LIKELY THIS WINTER. THIS IN PART LEADS TO VERY LOW PROBABILITIES ACROSS THE EAST COAST, WHERE LA NINA AND TRENDS WOULD TEND TO FAVOR A SLIGHTLY WARMER OUTCOME. MJO ACTIVITY COULD ALSO PLAY AN IMPORTANT ROLE. ONE OR TWO STRONG CONVECTIVE EVENTS OVER THE INDIAN OCEAN COULD FORCE A ROSSBY WAVE RESPONSE THAT WOULD TILT THE WINTER TOWARD THE WARMER OUTCOME INDICATED BY DYNAMICAL MODELS. HOWEVER, IF ENHANCED CONVECTION IS CENTERED FARTHER EAST OVER THE MARITIME CONTINENT AND FAR WESTERN PACIFIC, THE COLDER OUTCOME INDICATED BY STATISTICAL GUIDANCE IS MORE LIKELY ACROSS THE NORTHERN CONUS. HEADING INTO LATE WINTER AND EARLY SPRING, BELOW-NORMAL TEMPERATURES ARE EXPANDED AND SHIFTED WESTWARD TO INCLUDE NORTHERN AREAS OF THE ROCKIES AND PACIFIC NORTHWEST. BY MAM AND AMJ, THE STATISTICAL AND DYNAMICAL TOOLS COME INTO BETTER AGREEMENT, DEPICTING PROBABILITIES FAVORING ABOVE-NORMAL TEMPERATURES OVER THE SOUTHERN, CENTRAL, AND EASTERN CONUS. ABOVE NORMAL TEMPERATURES REMAIN FAVORED FROM DJF THROUGH AMJ ACROSS THE SOUTHERN TIER OF THE CONTIGUOUS U.S. WITH THE GREATEST PROBABILITIES OVER THE SOUTHWEST. THE OUTLOOKS FROM MJJ 2017 AND BEYOND PRIMARILY REFLECT INPUT FROM TRENDS, THE CCA, AND THE CONSTRUCTED ANALOG BASED ON GLOBAL SST AND FAVOR ABOVE-NORMAL TEMPERATURES FOR MUCH OF THE CONUS AND ALASKA. TRENDS IN SEA ICE EXTENT INCREASE PROBABILITIES FOR ABOVE-NORMAL TEMPERATURES FOR THE NORTH SLOPE OF ALASKA DURING SON AND OND 2017. BY WINTER 2017-2018, THE OUTLOOK IS MOSTLY INFLUENCED BY TRENDS DUE TO THE UNCERTAINTY REGARDING ENSO. WHILE LA NINA EVENTS OFTEN OCCUR BACK-TO-BACK, SUCH AN OUTCOME IS NOT FAVORED AT THIS TIME. PRECIPITATION THE DJF 2016-2017 PRECIPITATION OUTLOOK WAS PRIMARILY BASED ON CONSIDERATIONS OF LA NINA CONDITIONS (REGRESSIONS ANCHORED TO THE CPC SST CONSOLIDATION WITH TRENDS) AND RELATIVELY CONSISTENT SIGNALS IN CALIBRATED DYNAMICAL MODEL GUIDANCE FROM THE NMME. ABOVE-MEDIAN PRECIPITATION IS FAVORED FOR NORTHWEST ALASKA AND PORTIONS OF THE PACIFIC NORTHWEST, NORTHERN ROCKIES, NORTHERN GREAT PLAINS AND GREAT LAKES. BELOW MEDIAN PRECIPITATION IS FAVORED ACROSS THE SOUTHERN TIER OF THE CONTIGUOUS U.S. WITH THE GREATEST PROBABILITIES ALONG THE GULF COAST. IN ADDITION, BELOW-MEDIAN PRECIPITATION IS FAVORED DURING DJF 2016-2017 FOR COASTAL SOUTH-CENTRAL ALASKA SUPPORTED BY LA NINA CONSIDERATIONS AND DYNAMICAL MODEL GUIDANCE. THE PRECIPITATION OUTLOOK REMAINS SIMILAR, TO THE FIRST ORDER, THROUGH FMA 2017 WITH A FAVORED ACTIVE NORTHERN STREAM AND WETTER THAN AVERAGE CONDITIONS MOST LIKELY IN THE AFOREMENTIONED AREAS. COVERAGE FOR ABOVE-MEDIAN PRECIPITATION IS SLIGHTLY INCREASED IN DJF 2016-17 AND JFM 2017 IN SOME AREAS AS ANY LA NINA INFLUENCE LIKELY MAY BE MORE PRONOUNCED IN THESE SEASONS AND SIGNALS FROM THE DYNAMICAL MODEL GUIDANCE ARE SLIGHTLY STRONGER. BELOW-MEDIAN PRECIPITATION REMAINS FAVORED FOR THE SOUTHERN TIER DURING THESE SEASONS WITH THE LOWEST COVERAGE AND PROBABILITIES INDICATED IN FMA 2017. POSITIVE PRECIPITATION TRENDS CONTRIBUTE TO THE OUTLOOK ACROSS SOME AREAS OF THE NORTHERN PLAINS AND GREAT LAKES BEGINNING IN FMA 2017 AND THIS CONTINUES THROUGH MJJ 2017. A POSITIVE TREND SIGNAL IS ALSO EVIDENT AND DEPICTED ACROSS THE NORTHEAST CONUS FROM JJA 2017 THROUGH SON 2017. DRIER THAN AVERAGE CONDITIONS ARE FAVORED FOR MAM AND AMJ 2017 ACROSS THE SOUTHWEST BASED ON NEGATIVE HISTORICAL PRECIPITATION TRENDS. FOR NDJ AND DJF 2017-2018, BELOW-MEDIAN PRECIPITATION IS SLIGHTLY FAVORED OVER PARTS OF THE FAR SOUTHEASTERN CONUS AND THE WEST COAST CENTERED ON NORTHERN CALIFORNIA. THESE SIGNALS ARE EVIDENT IN THE VARIOUS STATISTICAL FORECAST TOOLS AND IS HEAVILY INFLUENCED BY 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/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 DEC 15 2016 1981-2010 BASE PERIOD MEANS WERE IMPLEMENTED EFFECTIVE WITH THE MAY 19, 2011 FORECAST RELEASE. $$