PROGNOSTIC DISCUSSION FOR LONG-LEAD SEASONAL OUTLOOKS NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD 830AM EDT THURSDAY AUG 21 2014 SUMMARY OF THE OUTLOOK FOR NON-TECHNICAL USERS THE MAIN FACTORS THAT USUALLY INFLUENCE THE SEASONAL CLIMATE OUTLOOK INCLUDE: 1) EL NINO AND LA NINA - WHICH TOGETHER COMPRISE EL NINO/SOUTHERN OSCILLATION OR ENSO. IMPACTS OF THESE EVENTS ARE SUMMARIZED BY SEPARATING 3-MONTH OBSERVATIONS FROM 3 OR MORE DECADES INTO EL NINO, NEUTRAL, AND LA NINA SETS, AVERAGING EACH SEPARATELY, AND THEN COMPUTING ANOMALIES. THESE ARE CALLED "ENSO COMPOSITES", WHICH ARE USED AT TIMES TO SUBJECTIVELY MODIFY THE FORECAST. 2) TRENDS - APPROXIMATED BY THE OCN TOOL AS THE DIFFERENCE BETWEEN THE MOST RECENT 10-YEAR MEAN OF TEMPERATURE OR 15-YEAR MEAN OF PRECIPITATION FOR A GIVEN LOCATION AND TIME OF YEAR AND THE 30-YEAR CLIMATOLOGICAL PERIOD (1981-2010). 3) THE MADDEN-JULIAN OSCILLATION (MJO) - AFFECTS CLIMATE VARIABILITY WITHIN SEASONS. 4) THE NORTH ATLANTIC OSCILLATION (NAO) AND THE PACIFIC - NORTH AMERICAN (PNA) PATTERNS - WHICH AFFECT ANOMALY PATTERNS ESPECIALLY DURING THE COLD SEASONS. THESE PHENOMENA ARE CONSIDERABLY LESS PREDICTABLE ON A SEASONAL TIMESCALE THAN ENSO. 5) THE PACIFIC DECADAL OSCILLATION (PDO) - AN ENSO-LIKE PATTERN OF CLIMATE VARIABILITY AFFECTING THE TROPICS AND THE NORTH PACIFIC AND NORTH AMERICAN REGIONS, BUT WHICH VARIES ON A MUCH LONGER TIMESCALE THAN ENSO. 6) PERSISTENTLY DRY OR WET SOILS IN THE SPRING AND SUMMER AND SNOW AND ICE COVER ANOMALIES IN THE WINTER. THESE FACTORS TEND TO PERSIST FOR LONG PERIODS AND ACT AS A KIND OF MEMORY IN THE CLIMATE SYSTEM. 7) STATISTICAL FORECAST TOOLS - CANONICAL CORRELATION ANALYSIS (CCA), SCREENING MULTIPLE LINEAR REGRESSION (SMLR), CONSTRUCTED ANALOGUE (CA) AND ENSEMBLE CCA (ECCA). 8) DYNAMICAL FORECAST MODELS - INCLUDING THE NCEP CLIMATE FORECAST SYSTEM (CFS). AN EXPERIMENTAL MODEL FORECAST SYSTEM, THE NATIONAL MULTI-MODEL ENSEMBLE, COMPRISED OF SEVERAL MODELS AND DESIGNATED NMME, MAY ALSO BE USED EXPERIMENTALLY AND SUBJECTIVELY UNTIL IT IS INCLUDED INTO THE CONSOLIDATION. AN INTERNATIONAL MULTI-MODEL ENSEMBLE DESIGNATED IMME IS ALSO AVAILABLE. 9) CONSOLIDATION (CON) - AN OBJECTIVE, SKILL-WEIGHTED COMBINATION OF THE OCN, CCA, SMLR, ECCA, AND CFS FORECASTS IS USED AS A FIRST GUESS IN PREPARING THE FORECAST MAPS. THIS TECHNIQUE MAKES OPTIMUM USE OF THE KNOWN SKILL OF FORECAST TOOLS. CURRENT ATMOSPHERIC AND OCEANIC OBSERVATIONS SUGGEST A TRANSITION FROM ENSO-NEUTRAL TO EL NINO CONDITIONS IS UNDERWAY, THOUGH THERE CONTINUES TO BE CONFLICTING INDICATIONS AND SIGNIFICANT UNCERTAINTY AS TO HOW STRONG THIS EL NINO MAY GET. A MAJORITY OF DYNAMICAL AND STATISTICAL MODEL PREDICTIONS OF EAST-CENTRAL EQUATORIAL PACIFIC SEA SURFACE TEMPERATURES (SSTS) FAVOR A WEAK EL NINO, PEAKING DURING THE LATE AUTUMN AND EARLY WINTER IN THE NORTHERN HEMISPHERE. THE TEMPERATURE OUTLOOK FOR SEPTEMBER-OCTOBER-NOVEMBER (SON) 2014 INDICATES ELEVATED ODDS OF ABOVE-NORMAL MEAN TEMPERATURES ACROSS THE WESTERN CONUS, THE ATLANTIC COAST STATES AS FAR SOUTH AS NORTHERN FLORIDA, AND MOST OF ALASKA. BELOW-NORMAL MEAN TEMPERATURES ARE FAVORED FROM CENTRAL PORTIONS OF THE GREAT PLAINS SOUTHWEST INTO CENTRAL NEW MEXICO. THE SON 2014 PRECIPITATION OUTLOOK CALLS FOR SLIGHTLY ENHANCED PROBABILITIES OF BELOW-MEDIAN PRECIPITATION ACROSS PORTIONS OF THE PACIFIC NORTHWEST. ELEVATED CHANCES FOR ABOVE-MEDIAN PRECIPITATION AMOUNTS ARE FORECAST FROM SOUTHERN CALIFORNIA AND EASTERN NEVADA EASTWARD ACROSS THE CENTRAL AND SOUTHERN ROCKIES, THE CENTRAL AND SOUTHERN GREAT PLAINS, AND WESTERN PORTIONS OF THE MIDDLE AND LOWER MISSISSIPPI VALLEY. THE ODDS FOR ABOVE-MEDIAN PRECIPITATION ARE ALSO ENHANCED OVER SOUTHERN FLORIDA AND MOST OF SOUTHERN ALASKA. IN AREAS WHERE THE LIKELIHOODS OF SEASONAL MEAN TEMPERATURES AND SEASONAL ACCUMULATED PRECIPITATION AMOUNTS ARE SIMILAR TO CLIMATOLOGICAL PROBABILITIES, EQUAL CHANCES (EC) IS SHOWN. 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 ATMOSPHERIC AND OCEANIC CONDITIONS IN THE PACIFIC BASIN INDICATE THAT A TRANSITION TO AN EL NINO CONTINUES, THOUGH THERE ARE CONFLICTING INDICATIONS AND CONSIDERABLE UNCERTAINTY REGARDING THE PEAK STRENGTH OF THIS PREDICTED WARM EVENT. THE LATEST WEEKLY OBSERVATIONS SHOW SST ANOMALIES OF +0.0 DEGREES C IN THE NINO 3.4 REGION, +0.4C IN NINO 4, +0.5C IN NINO 3, AND +1.2C IN NINO 1+2. SUB-SEASONAL VARIABILITY ACROSS THE TROPICS HAS SLOWED THE TRANSITION TO EL NINO IN RECENT WEEKS. THE SPATIAL DISTRIBUTION OF TROPICAL CONVECTION DURING THE PAST 30-DAYS IN THE WESTERN AND CENTRAL PACIFIC IS NOT CONSISTENT WITH AN EL NINO. ALTHOUGH THERE HAVE BEEN SOME AREAS OF SUPPRESSED CONVECTION OVER THE MARITIME CONTINENT REGION, IT HAS NOT BEEN A MORE COHERENT AND STABLE PATTERN OF SUPPRESSED CONVECTION. IN ADDITION, SUPPRESSED CONVECTION IS ALSO ALONG (BUT MOSTLY SOUTH OF) THE EQUATOR IN THE VICINITY OF THE DATE LINE, WHICH IS NOT CONSISTENT WITH A DEVELOPING WARM EVENT. LOW-LEVEL (850-HPA) WINDS WERE NEAR-AVERAGE ACROSS MOST OF THE EQUATORIAL PACIFIC DURING THIS SAME PERIOD. THE EXTRATROPICAL PACIFIC (POLEWARD OF 20N) CURRENTLY PROJECTS ONTO A POSITIVE PDO PATTERN, THOUGH SIGNIFICANTLY LESS THAN LAST MONTH, WITH THE CURRENT PDO INDEX VALUE AT +0.70. THE STATE OF THE NORTHERN ATLANTIC OCEAN IS ALSO A BIT DIFFERENT THAN IN RECENT YEARS, WITH THE MOST RECENT INDEX VALUE OF THE AMO BEING SLIGHTLY MORE POSITIVE THAN THAT FROM LAST MONTH. PROGNOSTIC DISCUSSION OF SST FORECASTS MOST STATISTICAL AND DYNAMICAL MODELS CONTINUE TO SUGGEST THAT AN EL NINO WILL EMERGE WITHIN THE NEXT 3-6 WEEKS. A GENERAL CONSENSUS FAVORS A WEAK WARM EVENT (ONI RANGING BETWEEN +0.5C AND +0.9C), PEAKING DURING THE LATE AUTUMN AND EARLY WINTER, WHILE A FEW SOLUTIONS FAVOR A MODERATE EVENT. THE CFS IS AMONG THE WARMEST OF PREDICTIONS, WITH THE CFS ENSEMBLE MEAN PEAKING IN LATE AUTUMN AND EARLY WINTER AT MODERATE STRENGTH (+1.2C), WITH MOST INDIVIDUAL MEMBERS RANGING FROM ABOUT +0.8C TO +1.5C, WITH A GRADUAL DECLINE OF SST ANOMALIES THROUGH WINTER AND EARLY SPRING. THE CPC CONSOLIDATION (CPC CON) FORECASTS A MAXIMUM SST ANOMALY OF ABOUT +0.8C (WEAK EL NINO) IN NDJ 2014/15, DECREASING IN MAGNITUDE TO BORDERLINE NEUTRAL CONDITIONS (+0.5C) BY FMA 2015. THE NMME PREDICTS A BORDERLINE EL NINO (+0.5C) BY SEPTEMBER, AND SLOWLY INCREASING TO A MAXIMUM VALUE OF +1.0 (BORDERLINE MODERATE EL NINO) BY LATE WINTER. THE IMME SST ANOMALY PLUME IS SIMILAR TO THE NMME PLUME, EXCEPT IT TOPS OUT AROUND +0.8C (WEAK EL NINO) BY LATE WINTER. PROGNOSTIC TOOLS USED FOR U.S. TEMPERATURE AND PRECIPITATION OUTLOOKS THE TEMPERATURE AND PRECIPITATION OUTLOOKS WERE MADE CONSIDERING EL NINO CONDITIONS TO BE A FACTOR IN AUTUMN AND WINTER. GUIDANCE FROM THE CFS AS WELL AS THE NMME AND IMME AND THEIR ASSOCIATED COMPONENTS CONTRIBUTED TO THE OUTLOOKS FROM SON THROUGH NDJ 2014, ESPECIALLY WHERE THEIR ANOMALIES AGREED WITH COMPOSITES FROM DEVELOPING WARM ENSO EVENTS. FROM DJF 2014/15 THROUGH FMA 2015, LESS WEIGHT WAS PLACED ON THE DYNAMICAL INPUTS SUCH AS THE CFS, NMME, AND IMME, AND MORE ON TRADITIONAL ENSO COMPOSITES. THE DYNAMICAL SOLUTIONS APPEAR TO BE TOO WARM OVER MOST OF THE CONUS GIVEN THE EXPECTATION OF A WEAK EL NINO DURING THE WINTER, AND AREAS OF COVERAGE AND PROBABILITIES WERE REDUCED ACCORDINGLY FROM THE PREVIOUS MONTH'S SET OF OUTLOOKS VALID FROM DJF TO FMA. FROM MAM TO SON 2015, THE TEMPERATURE OUTLOOKS ARE BASED PRIMARILY ON THE CONSOLIDATION (CON) TOOL WHICH INCORPORATES HISTORICAL TEMPERATURE TRENDS, WHILE FOR PRECIPITATION, MOST INDICATIONS WERE EITHER WEAK OR CONFLICTING, FAVORING A FORECAST OF EC. THE EXCEPTIONS FOR PRECIPITATION INCLUDED JJA AND JAS 2015, WHERE DRIER TRENDS ARE FAVORED IN THE CENTRAL INTERMOUNTAIN REGION. PROGNOSTIC DISCUSSION OF OUTLOOKS - SON 2014 TO SON 2015 TEMPERATURE THE SON THROUGH NDJ 2014-15 TEMPERATURE OUTLOOKS INDICATE ELEVATED PROBABILITIES OF ABOVE-NORMAL SEASONAL MEAN TEMPERATURES FOR NEARLY ALL OF ALASKA. ELEVATED PROBABILITIES OF ABOVE-NORMAL SEASONAL MEAN TEMPERATURES ARE ALSO FORECAST FOR MUCH OF THE WEST, AND ATLANTIC COAST STATES AS FAR SOUTH AS NORTHERN FLORIDA (SON), WITH THE PREDICTED TRANSITION TO ABOVE-NORMAL TEMPERATURES ACROSS THE NORTHERN HALF OF THE CONUS BY NDJ. BELOW-NORMAL SEASONAL MEAN TEMPERATURES ARE FAVORED FROM CENTRAL PORTIONS OF THE GREAT PLAINS SOUTHWEST INTO CENTRAL NEW MEXICO. THESE EARLY LEAD OUTLOOKS ARE BASED PRIMARILY ON THE CFS, NMME, IMME, CON, IRI, AND ENSO COMPOSITES. THE AREA OF PREDICTED BELOW-NORMAL TEMPERATURES IS BASED ON COMPOSITES OF THE CURRENT PHASE OF THE PDO AND DEVELOPING WARM EVENTS, AND THE SMLR. FROM DJF 2014/15 THROUGH FMA 2015, THE SAME TOOLS NOTED ABOVE WERE CONSIDERED, WITH A GREATER EMPHASIS ON ENSO COMPOSITES (THOUGH WITH DIMINISHED COVERAGE AND PROBABILITIES DEEMED MORE APPROPRIATE FOR AN EXPECTED WEAK WARM EVENT). THESE OUTLOOKS INDICATE THE ANTICIPATED EXPANSION OF BELOW-NORMAL TEMPERATURES ACROSS FLORIDA AND THE GULF COAST, CONSISTENT WITH AN ENHANCED SUBTROPICAL JET STREAM. THE MAM 2015 OUTLOOK FAVORS THE WINDING DOWN OF THE PREDICTED EL NINO, WHILE ALL SUBSEQUENT LEADS ARE BASED ALMOST ENTIRELY ON THE CON AND LONG-TERM TEMPERATURE TRENDS. IN AREAS WITHOUT SUBSTANTIAL AND RELIABLE CLIMATE SIGNALS, EQUAL CHANCES OF BELOW-, NEAR- AND ABOVE-NORMAL SEASONAL MEAN TEMPERATURES ARE INDICATED. PRECIPITATION THROUGH AUTUMN 2014, THERE ARE FAIRLY STRONG AND CONSISTENT INDICATIONS FROM THE CFS, NMME, AND IMME FOR ABOVE-MEDIAN PRECIPITATION AMOUNTS VARYING THROUGHOUT PORTIONS OF SOUTHERN CALIFORNIA, THE SOUTHWEST, CENTRAL AND SOUTHERN PORTIONS OF BOTH THE ROCKIES AND GREAT PLAINS, AND CENTRAL AND SOUTHERN PORTIONS OF THE MISSISSIPPI VALLEY. ABOVE-MEDIAN PRECIPITATION AMOUNTS ARE ALSO ENHANCED OVER FLORIDA AND SOUTHERN ALASKA. THIS IS ALSO CONSISTENT WITH THE EARLY STAGES OF AN EL NINO. ENHANCED ODDS OF BELOW-MEDIAN PRECIPITATION ARE INDICATED OVER THE NORTHWEST, BASED LARGELY ON THE CFS MODEL (BUT ALSO TO SOME EXTENT ON THE IMME AND IRI). AS SEASONS PROGRESS INTO WINTER, THE OUTLOOKS REFLECT THE PRECIPITATION PATTERNS ASSOCIATED WITH EL NINO EVENTS, WITH ABOVE-MEDIAN PRECIPITATION AMOUNTS FAVORED THROUGHOUT MUCH OF THE SOUTHERN CONUS IN ASSOCIATION WITH AN EXPECTED ACTIVE SOUTHERN STREAM, AND A TENDENCY FOR BELOW-MEDIAN AMOUNTS NEAR THE OHIO RIVER VALLEY AND ALSO IN PARTS OF THE NORTHERN ROCKIES. BOTH THE SPATIAL COVERAGE AND PROBABILITIES HAVE BEEN DIMINISHED SOMEWHAT FROM THE PREVIOUS SET OF OUTLOOKS VALID FOR THESE SAME TARGET SEASONS. AS NOTED ABOVE, THESE ADJUSTMENTS WERE MADE TO BETTER ACCOUNT FOR AN EXPECTED WEAK EL NINO. THE PRECIPITATION OUTLOOK FOR MAM 2015 AND BEYOND SHOW EQUAL CHANCES FOR BELOW-, NEAR- AND ABOVE-MEDIAN SEASONAL ACCUMULATED PRECIPITATION THROUGHOUT THE CONUS AND ALASKA, WITH ONE EXCEPTION. FOR THE SEASONS OF JJA AND JAS 2015, HISTORICAL PRECIPITATION TRENDS FAVOR DRYNESS ACROSS PORTIONS OF THE CENTRAL INTERMOUNTAIN REGION. 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/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 SEP 18 2014 1981-2010 BASE PERIOD MEANS WERE IMPLEMENTED EFFECTIVE WITH THE MAY 19, 2011 FORECAST RELEASE. $$