PROGNOSTIC DISCUSSION FOR LONG-LEAD SEASONAL OUTLOOKS NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD 830 AM EDT THU AUG 18 2016 SUMMARY OF THE OUTLOOK FOR NON-TECHNICAL USERS THE CURRENT OCEANIC AND ATMOSPHERIC STATE INDICATES ENSO-NEUTRAL CONDITIONS, WITH A TRANSITION TO WEAK LA NINA CONDITIONS EXPECTED DURING THE AUG-SEP-OCT (ASO) 2016 SEASON. THE LATEST CPC/IRI CONSENSUS ENSO FORECAST DEPICTS A PROBABILITY OF 55-60 PERCENT FOR A WEAK LA NINA DURING THE AUTUMN AND EARLY WINTER. THE SON 2016 TEMPERATURE OUTLOOK INDICATES INCREASED PROBABILITIES OF ABOVE-NORMAL TEMPERATURES ACROSS THE ENTIRE CONTIGUOUS U.S. AND ALASKA. DYNAMICAL MODEL SUPPORT AND/OR HISTORICAL TRENDS FAVOR PROBABILITIES IN EXCESS OF 50 PERCENT ACROSS THE SOUTHWESTERN STATES, GULF COAST REGION, THE EASTERN GREAT LAKES AND NEW ENGLAND, AND THE NORTHERN AND SOUTHERN THIRDS OF ALASKA. THE GREATEST PROBABILITIES OF ABOVE-NORMAL MEAN TEMPERATURES ARE IN EXCESS OF 70 PERCENT ACROSS THE NORTH SLOPE OF ALASKA. THIS IS LARGELY DUE TO WARMING TRENDS OVER THE PAST FEW DECADES AND THE ASSOCIATED DELAYED ONSET OF SEA ICE FORMATION (AND REDUCED COVERAGE OF MULTI-YEAR ICE) ACROSS THE NEARBY ARCTIC OCEAN. THE SON 2016 PRECIPITATION OUTLOOK INDICATES INCREASED PROBABILITIES OF ABOVE-MEDIAN PRECIPITATION ACROSS THE NORTHERN GREAT PLAINS AND ALASKA PANHANDLE, BASED PRIMARILY ON AVAILABLE CLIMATE MODEL GUIDANCE. BELOW-MEDIAN PRECIPITATION IS FAVORED IN NEVADA AND ADJACENT PARTS OF CALIFORNIA, AS WELL AS OVER THE LOWER MISSISSIPPI VALLEY, THE INTERIOR SOUTHEAST, TENNESSEE, THE SOUTHERN APPALACHIANS, AND MUCH OF KENTUCKY. THIS IS BASED ON MODEL GUIDANCE, AND ON HISTORICAL PRECIPITATION TRENDS FOR THE SON SEASON. 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 PACIFIC SST ANOMALIES ARE MOSTLY 1-2 DEGREES C BELOW AVERAGE CLOSE TO THE EQUATOR FROM ABOUT 170W EASTWARD TO 100W, WHILE ABOVE AVERAGE SSTS PREVAIL FROM ABOUT 170E TO THE MARITIME CONTINENT. THE MOST RECENT THREE-MONTH AVERAGE NINO 3.4 SST ANOMALY IS +0.18 DEGREE C FOR MJJ. THE LATEST WEEKLY NINO 3.4 ANOMALY HAS NOW DECREASED TO -0.5 DEGREE C. A LARGE RESERVOIR OF ANOMALOUSLY COOL SUBSURFACE WATERS EXTENDS TO MORE THAN 150 METERS BELOW THE SURFACE, WITH THE LARGEST NEGATIVE ANOMALIES 3-4 DEGREES C BELOW AVERAGE AT A DEPTH OF ABOUT 125 METERS, BETWEEN 140W-160W. POSITIVE OLR ANOMALIES (SUPPRESSED CONVECTION) WERE PRESENT OVER THE EQUATORIAL PACIFIC, WHILE NEGATIVE OLR ANOMALIES (ENHANCED CONVECTION) IS PRESENT OVER INDONESIA, DURING THE PAST 30-DAYS. LOW-LEVEL, EASTERLY TRADE WINDS AT THE 850-HPA LEVEL HAVE BEEN NEAR AVERAGE DURING THE PAST MONTH, WHILE THE UPPER-LEVEL, 200-HPA WINDS ARE ANOMALOUSLY WESTERLY OVER THE EQUATORIAL PACIFIC FROM THE DATE LINE EASTWARD TO 150W. ANOMALOUS INTEGRATED EQUATORIAL PACIFIC OCEAN HEAT CONTENT FROM THE SURFACE TO 300 METERS DEPTH HAS BEEN PERSISTENTLY NEGATIVE FOR THE LAST SEVERAL MONTHS. NEGATIVE OCEAN HEAT CONTENT ANOMALIES INCREASE THE CHANCE OF DEVELOPMENT OF LA NINA CONDITIONS DURING THE REMAINDER OF 2016. THE EXTRATROPICAL PACIFIC OCEAN REMAINS CONSISTENT WITH THE POSITIVE PHASE OF THE PACIFIC DECADAL OSCILLATION (PDO) WITH ABOVE AVERAGE SSTS IN THE NORTH PACIFIC, AND TO THE SOUTH OF ALASKA, AND ALONG THE COAST OF SOUTHERN CALIFORNIA. POSITIVE SST ANOMALIES PERSIST IN THE WESTERN ATLANTIC NEAR THE U.S. EAST COAST, AND THE THE GULF OF MEXICO. PROGNOSTIC DISCUSSION OF SST FORECASTS THE CPC SST CONSOLIDATION PREDICTS A WEAK LA NINA BEGINNING IN ASO 2016 AND CONTINUING THROUGHOUT THE AUTUMN AND MUCH OF WINTER, WITH A PEAK AMPLITUDE IN SST ANOMALY OF -0.7 DEGREE C BELOW AVERAGE DURING THE DJF 2016-17 SEASON. PREDICTIONS FROM THE NORTH AMERICAN MULTI-MODEL ENSEMBLE (NMME) MEMBERS INDICATE A RANGE OF NINO 3.4 ANOMALIES, WITH THE ENSEMBLE MEAN NEAR -0.5 C FROM AUGUST THROUGH DECEMBER. THE CPC/IRI CONSENSUS FORECAST INDICATES LA NINA IS SLIGHTLY FAVORED TO DEVELOP DURING ASO 2016, WITH ABOUT A 55-60 PERCENT CHANCE OF LA NINA DURING THE AUTUMN AND WINTER 2016-17. PROGNOSTIC TOOLS USED FOR U.S. TEMPERATURE AND PRECIPITATION OUTLOOKS CALIBRATED PROBABILISTIC FORECASTS FROM THE NMME PROVIDE THE PRIMARY GUIDANCE FOR THE SEASONAL OUTLOOK FOR SON 2016. THE PREDICTED TRANSITION TO LA NINA CONDITIONS AND THE MOST LIKELY IMPACTS ARE CONSIDERED FOR THE SEASONAL OUTLOOKS PRIMARILY BEGINNING IN OND 2016 THROUGH THE WINTER INTO EARLY SPRING, 2017. IN ADDITION TO DYNAMICAL MODEL GUIDANCE FROM THE NMME, THE SEASONAL OUTLOOKS ARE ALSO BASED ON THE NCEP CLIMATE FORECAST SYSTEM (CFS), THE INTERNATIONAL MULTI-MODEL ENSEMBLE (IMME), A SST-BASED CONSTRUCTED ANALOG AND OTHER ADDITIONAL STATISTICAL TOOLS, INCLUDING REGRESSION-BASED IMPACTS OF ENSO, AND DECADAL TRENDS INHERENT IN THE CPC CONSOLIDATION (CON) TOOL. PROGNOSTIC DISCUSSION OF OUTLOOKS - SON 2016 TO SON 2017 TEMPERATURE THE TEMPERATURE OUTLOOK FOR SON 2016 IS SIMILAR TO THE OUTLOOK MADE LAST MONTH FOR THE SAME TARGET PERIOD. ABOVE NORMAL MEAN TEMPERATURES ARE FAVORED ACROSS THE ENTIRE CONTIGUOUS UNITED STATES AND ALASKA. THE GREATEST PROBABILITIES FOR THE CONUS INCLUDE THE SOUTHWESTERN STATES (IN EXCESS OF 60 PERCENT), THE GULF COAST ENVIRONS AND FROM THE EASTERN GREAT LAKES TO THE NORTHERN ATLANTIC COAST (IN EXCESS OF 50 PERCENT). FOR ALASKA, THE GREATEST PROBABILITIES OF ABOVE NORMAL TEMPERATURES INCLUDE THE SOUTHERN THIRD OF THE STATE (IN EXCESS OF 60 PERCENT), AND THE NORTHERN THIRD OF ALASKA (GREATER THAN 70 PERCENT). THESE AREAS ARE BASED ON THE LATEST AVAILABLE CLIMATE MODELS, SUCH AS THE CALIBRATED PROBABILITIES FROM THE NATIONAL MULTI-MODEL ENSEMBLE (PAC), IMME, CFS, CANADIAN MODELS, AND ON HISTORICAL TRENDS. A BROAD AREA OF SLIGHTLY ENHANCED PROBABILITIES FOR ABOVE NORMAL TEMPERATURES (33-40 PERCENT) IS INDICATED FROM THE FAR NORTHERN ROCKIES EASTWARD TO THE UPPER MISSISSIPPI VALLEY. THIS REPRESENTS THE EARLY EFFECTS OF A DEVELOPING WEAK LA NINA. THE TEMPERATURE OUTLOOKS FROM OND 2016 THROUGH AMJ 2017 INCLUDE THE ANTICIPATED IMPACTS OF A WEAK LA NINA. APPROXIMATELY THE SOUTHERN HALF OF THE CONUS IS FAVORED TO HAVE ABOVE NORMAL TEMPERATURES THROUGHOUT THESE LEADS, WITH THE HIGHEST PROBABILITIES EXPECTED ACROSS THE SOUTHWESTERN STATES (IN EXCESS OF 50 PERCENT FROM OND 2016 THROUGH MAM 2017). CLIMATE MODELS AND HISTORICAL TRENDS WERE ALSO INCORPORATED INTO THESE OUTLOOKS. FOR APPROXIMATELY THE NORTHERN HALF OF THE CONUS, HOWEVER, A COMBINATION OF BELOW NORMAL TEMPERATURES AND EC IS FAVORED THROUGHOUT THESE LEADS. STARTING IN OND, A SMALL AREA OF EC IS FAVORED ACROSS THE NORTHERN GREAT PLAINS, AND ABOVE NORMAL TEMPERATURES ARE FAVORED THROUGHOUT THE REMAINDER OF THE NORTHERN CONUS. THE HIGHEST PROBABILITIES (IN EXCESS OF 40 PERCENT) ARE INDICATED OVER THE EASTERN GREAT LAKES AND THE NORTHEAST, DUE TO A COMBINATION OF TEMPERATURE TRENDS AND CLIMATE MODEL GUIDANCE. DURING NDJ, THE AREA OF PREDICTED EC EXPANDS EASTWARD AND SOUTHEASTWARD TO INCLUDE MOST OF THE REMAINDER OF THE NORTHERN CONUS. THE EXCEPTION IS NORTHERN NEW ENGLAND, WHERE LINGERING ABOVE NORMAL TEMPERATURES ARE FAVORED. FROM DJF 2016-17 THROUGH AMJ 2017, AN AREA OF BELOW NORMAL TEMPERATURES IS EXPECTED TO DEVELOP, INITIALLY OVER THE NORTHERN PLAINS AND UPPER MISSISSIPPI VALLEY, FOLLOWED BY EASTWARD EXPANSION TO MICHIGAN AND WESTWARD EXPANSION TO WASHINGTON AND OREGON DURING JFM AND FMA 2017. BY MAM AND AMJ 2017, THE COVERAGE OF BELOW NORMAL TEMPERATURES IS EXPECTED TO DIMINISH IN SIZE, WITH ABOVE NORMAL TEMPERATURES ANTICIPATED TO SHIFT INTO THE MID-ATLANTIC AND SOUTHERN GREAT LAKES BY AMJ. THE LATTER LEADS, MJJ THROUGH SON 2017, ARE PRIMARILY BASED ON LONGER-TERM TEMPERATURE TRENDS, WITH ELEVATED PROBABILITIES OF ABOVE NORMAL TEMPERATURES ACROSS MUCH OF THE CONUS. IN ALASKA, HISTORICAL TEMPERATURE TRENDS AND MOST OF THE AVAILABLE CLIMATE MODEL GUIDANCE FAVOR ABOVE NORMAL TEMPERATURES FOR THE FIRST TWO LEADS. THE EXPECTATION OF A WEAK LA NINA FORMS THE BASIS FOR EC INCREASING IN COVERAGE ACROSS THE SOUTHERN PORTION OF THE STATE DURING NDJ AND DJF. BELOW NORMAL TEMPERATURES ARE FAVORED TO DEVELOP ACROSS THE PANHANDLE AND SOUTHEAST PART OF THE MAINLAND DURING JFM AND FMA, AND ABOVE NORMAL TEMPERATURES ARE FORECAST TO PERSIST OVER NORTHWESTERN ALASKA. FROM MAM TO SON 2017, THE ALASKA TEMPERATURE OUTLOOK IS PRIMARILY ATTRIBUTED TO TRENDS, WITH ABOVE NORMAL TEMPERATURES FAVORED INITIALLY ACROSS THE NORTH SLOPE DURING MAM AND AMJ, WHICH THEN EXPANDS SOUTHWARD TO INCLUDE THE ENTIRE STATE BY JAS, ASO, AND SON 2017. PRECIPITATION THE PRECIPITATION OUTLOOKS ARE BASED ON CLIMATE MODEL GUIDANCE AND HISTORICAL PRECIPITATION TRENDS, WITH TRENDS BEING ESPECIALLY FAVORED DURING THE LATTER LEADS. IN SON, ABOVE MEDIAN PRECIPITATION IS PREDICTED ACROSS THE NORTHERN PLAINS AND THE ALASKA PANHANDLE, WHILE BELOW MEDIAN PRECIPITATION IS EXPECTED ACROSS NEVADA AND ADJACENT PARTS OF CALIFORNIA, AND MUCH OF THE SOUTHEASTERN QUARTER OF THE CONUS. FROM OND 2016 THROUGH MAM 2017, THE ANTICIPATED IMPACTS OF A WEAK LA NINA ARE DEPICTED. THESE IMPACTS INCLUDE ABOVE MEDIAN PRECIPITATION EXPANDING WESTWARD TO INCLUDE THE NORTHERN ROCKIES AND PACIFIC NORTHWEST, WHICH REDUCES IN SIZE BY FMA AND MAM TO INCLUDE THE PACIFIC NORTHWEST. ABOVE MEDIAN PRECIPITATION IS ALSO FAVORED TO DEVELOP ACROSS THE GREAT LAKES, OHIO VALLEY, EASTERN PORTIONS OF THE UPPER AND MIDDLE MISSISSIPPI VALLEY, AND THE TENNESSEE VALLEY DURING THE DJF, JFM, AND FMA SEASONS. THIS WET SIGNAL IS OFTEN OBSERVED DURING LA NINA WINTERS, AND USUALLY WINDS DOWN DURING MAM AND AMJ. IN CONTRAST, BELOW MEDIAN PRECIPITATION IS FAVORED TO INCREASE IN AREAL COVERAGE DURING OND AND NDJ TO INCLUDE MOST OF THE SOUTHERN CONUS. THIS RELATIVELY DRY SIGNAL IS FORECAST TO CONTINUE ACROSS THE SOUTHERN STATES THROUGH THE MAM SEASON, AS IS TYPICAL OF LA NINA WINTERS. BY AMJ 2017, THE PRECIPITATION OUTLOOKS ARE BASED ALMOST EXCLUSIVELY ON HISTORICAL TRENDS AS INDICATED BY THE CPC CONSOLIDATION TOOL. ABOVE MEDIAN PRECIPITATION IS FAVORED ACROSS THE GREAT LAKES IN AMJ AND MJJ, WHICH SHIFTS EASTWARD TO THE NORTHEAST STATES DURING JJA, JAS, AND ASO, WITH A RESIDUAL WET SIGNAL REMAINING OVER MAINE BY SON 2017. DURING JJA AND JAS, A DRY TREND IS FAVORED OVER THE PACIFIC NORTHWEST AND NORTHERN ROCKIES. IN ALASKA, CLIMATE MODEL GUIDANCE GENERALLY SUPPORTS ABOVE MEDIAN PRECIPITATION FOR THE PANHANDLE IN BOTH SON AND OND, WITH THE WET SIGNAL SHIFTING TO FAR NORTHERN AND WESTERN ALASKA DURING THE SUBSEQUENT 3 SEASONS (NDJ, DJF, AND JFM). BELOW MEDIAN PRECIPITATION IS FAVORED ACROSS THE SOUTHERN COAST OF MAINLAND ALASKA FROM NDJ THROUGH JFM. THIS IS A COMMON FEATURE OF LA NINA WINTERS. FOR FMA 2017 AND BEYOND, THERE IS NO DISCERNIBLE TILT IN THE ODDS TOWARDS ANY ONE PRECIPITATION CATEGORY. FORECASTER: ANTHONY ARTUSA 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 SEP 15 2016 1981-2010 BASE PERIOD MEANS WERE IMPLEMENTED EFFECTIVE WITH THE MAY 19, 2011 FORECAST RELEASE. $$