PROGNOSTIC DISCUSSION FOR LONG-LEAD SEASONAL OUTLOOKS NWS CLIMATE PREDICTION CENTER CAMP SPRINGS MD 830 AM EST THU NOV 19 2009 SUMMARY OF THE OUTLOOK FOR NON-TECHNICAL USERS THE MAIN FACTORS WHICH USUALLY INFLUENCE THE SEASONAL CLIMATE OUTLOOK INCLUDE: 1) EL NINO AND LA NINA - WHICH 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", AND ARE USED 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 CLIMATOLOGY PERIOD (CURRENTLY 1971-2000). 3) THE TROPICAL 30-60 DAY OSCILLATION - SOMETIMES CALLED MADDEN JULIAN OSCILLATION (MJO) - AFFECTS CLIMATE VARIABILITY WITHIN SEASONS. 4) THE NORTH ATLANTIC OSCILLATION (NAO) AND THE PACIFIC NORTH AMERICAN (PNA) PATTERNS - WHICH AFFECT THE TEMPERATURE ANOMALY PATTERN ESPECIALLY DURING THE COLD SEASONS. THESE PHENOMENA ARE CURRENTLY KNOWN TO BE PREDICTABLE ONLY OVER A WEEK OR SO. 5) THE PACIFIC DECADAL OSCILLATION (PDO) - AN ENSO-LIKE PATTERN OF CLIMATE VARIABILITY AFFECTING BOTH THE TROPICS AND THE NORTH PACIFIC AND NORTH AMERICAN REGIONS, BUT WHICH VARIES ON A MUCH LONGER TIME-SCALE THAN ENSO. 6) PERSISTENTLY DRY OR WET SOILS IN THE 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). 9) AN OBJECTIVE CONSOLIDATION (ABBREVIATED CON IN THE TEXT) 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 OUR FORECAST TOOLS. CURRENTLY MODERATE EL NINO CONDITIONS EXIST IN THE TROPICAL PACIFIC. THEY MAY HAVE BE AT MAXIMUM STRENGTH RIGHT NOW AND ARE EXPECTED TO PERSIST INTO THE 2009-10 NORTHERN HEMISPHERE WINTER. THE LIKELIHOOD OF A CONTINUING EL NINO EVENT INFLUENCES THE TEMPERATURE AND PRECIPITATION OUTLOOKS FOR DJF 2009-10 THROUGH MAM 2010, MAINLY VIA EL NINO COMPOSITES. THE IMPACT OF EL NINO ON THE CLIMATE OVER NORTH AMERICA HAS HISTORICALLY BEEN THE GREATEST DURING THE WINTER SEASONS. A STRONG EVENT IS LESS LIKELY, BUT STILL POSSIBLE. UNCERTAINTY IN THE FUTURE STRENGTH AND DURATION OF THIS EVENT IS CONSIDERED IN THE SEASONAL FORECASTS, ESPECIALLY AT LONGER LEAD TIMES. THE TEMPERATURE OUTLOOK FOR DJF 2009-10 INDICATES AN ENHANCED LIKELIHOOD OF ABOVE AVERAGE TEMPERATURES FOR MUCH OF THE WESTERN HALF OF THE CONUS AND ALASKA, AND ESPECIALLY SO IN THE NORTHERN ROCKIES ALONG THE CANADIAN BORDER. BELOW NORMAL TEMPERATURES ARE LIKELY FROM CENTRAL TEXAS ALONG THE GULF COAST TO THE MID-ATLANTIC. IN LOCATIONS WHERE THE CHANCE OF ABOVE OR BELOW AVERAGE SEASONAL MEAN TEMPERATURES ARE SIMILAR TO A RANDOM DRAW FROM THE HISTORICAL RECORD (CLIMATOLOGY), EQUAL CHANCES OF BELOW, NEAR, AND ABOVE AVERAGE ARE INDICATED. BELOW MEDIAN PRECIPITATION IS MOST LIKELY DURING DJF 2009-10 FOR PARTS OF THE PACIFIC NORTHWEST AND THE OHIO VALLEY. ABOVE MEDIAN PRECIPITATION AMOUNTS ARE MOST LIKELY IN TEXAS, FLORIDA, AND IN CALIFORNIA, AND NORTHERN SECTIONS OF ALASKA. IN LOCATIONS WHERE THE LIKELIHOOD OF ABOVE OR BELOW MEDIAN SEASONAL PRECIPITATION IS SIMILAR TO THE CLIMATOLOGICAL PROBABILITIES, EQUAL CHANCES OF BELOW, NEAR, AND ABOVE MEDIAN PRECIPITATION ARE INDICATED. 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 WEEKLY SEA SURFACE TEMPERATURE (SST) ANOMALIES HAVE RAPIDLY WARMED IN LATE OCTOBER AND EARLY NOVEMBER, AND EXCEED +1.5 CELSIUS ACROSS MUCH OF THE EQUATORIAL PACIFIC OCEAN AND ARE LOCALLY OVER +2C CELSIUS FROM THE DATE LINE EAST TO 130W. OUTGOING LONGWAVE RADIATION ANOMALIES ARE NOT YET IN SYNC WITH AN EL NINO EVENT. TRADE WINDS WERE VERY WEAK IN MID TO LATE OCTOBER BUT ARE CLOSE TO NORMAL AT PRESENT. SUBSURFACE HEAT CONTENT IS GENERALLY ABOVE NORMAL IN THE UPPER 200 METERS OF THE TROPICAL PACIFIC OCEAN WITH WATER TEMPERATURE ANOMALIES EXCEEDING +5 CELSIUS AT THERMOCLINE DEPTH NEAR 130W, MUCH MORE THAN A MONTH AGO. HISTORICALLY, POSITIVE TEMPERATURE ANOMALIES IN THE UPPER OCEAN PRECEDE THE ONSET AND FURTHER DEVELOPMENT OF EL NINO EVENTS. THUS TROPICAL PACIFIC TEMPERATURES ARE UNLIKELY TO RETURN TO AN ENSO NEUTRAL STATE PRIOR TO SPRING 2010. PROGNOSTIC DISCUSSION OF SST FORECASTS THE CURRENT MEAN PDF CORRECTED ENSEMBLE CFS FORECAST INDICATES SST ANOMALIES IN THE NINO 3.4 REGION PRESENTLY AT PEAK NEAR +1.5 CELSIUS, THUS CALLING FOR MODERATE TO STRONG EL NINO CONDITIONS BUT NO FURTHER STRENGTHENING. THE CPC STATISTICAL MODELS ARE GENERALLY FORECASTING A MODERATE EL NINO EVENT PEAKING BETWEEN +1 TO +1.5 DEGREES CELSIUS DURING THE EARLY PART OF THE WINTER. THE CPC CONSOLIDATION OF NINO 3.4 SST TEMPERATURE ANOMALY FORECASTS INDICATES THAT THE CURRENT EL NINO WILL LIKELY WEAKEN AND END BY MAM OR AMJ 2010. THE CFS FORECAST IS NO LONGER AMONG THE WARMEST ONES IN THE IRI MULTI-MODEL ENSEMBLE PLUME AND CONSENSUS BY EYE OF THE IRI PLUME AGREES WELL WITH CPC'S CONSOLIDATION FORECAST. PROGNOSTIC TOOLS USED FOR U.S. TEMPERATURE AND PRECIPITATION OUTLOOKS THE TEMPERATURE AND PRECIPITATION OUTLOOKS ARE BASED ON THE CONSOLIDATION FORECAST, A SKILL-WEIGHTED AND CALIBRATED PROBABILISTIC FORECAST DERIVED FROM THE CFS, SMLR, OCN, CCA, AND ECCA FORECAST TOOLS. EL NINO COMPOSITES ARE THE MAJOR FORECAST TOOL FOR FORECASTS FROM DJF 2009-10 THROUGH MAM 2010. THE CFS WAS RELIED UPON TO A CONSIDERABLE DEGREE. ITS FORECASTS HAVE BEEN CONSISTENT WITH DEVELOPING EL NINO CONDITIONS, THOUGH POSSIBLY ON THE TOO-INTENSE SIDE EARLY ON. PROGNOSTIC DISCUSSION OF OUTLOOKS - DJF 2009 TO DJF 2010 TEMPERATURE: THE TEMPERATURE OUTLOOKS FOR DJF 2009-10 THROUGH DJF 2010-11 INDICATE THAT THREE-MONTH MEAN TEMPERATURES ARE MOST LIKELY TO BE IN THE ABOVE NORMAL CATEGORY FOR MUCH OF THE WESTERN U.S. MAINLY DUE TO COMPOSITES, AND THE CONSOLIDATION. ALL OUTLOOKS USE THE CPC CONSOLIDATION FORECAST AS A STARTING POINT WITH MODIFICATIONS DUE TO THE INFLUENCE OF THE EXPECTED IMPACT OF EL NINO FROM DJF THROUGH MAM. SEASONAL MEAN TEMPERATURES ARE MOST LIKELY TO BE IN THE BELOW AVERAGE CATEGORY FOR THE SOUTHEAST, SECTIONS OF THE MID-ATLANTIC AND ALONG THE GULF COAST REGIONS FROM DJF 2009 TO FMA 2010 AS A RESULT OF EL NINO. THE LIKELIHOOD OF ABOVE AVERAGE TEMPERATURES IN THE NORTH-CENTRAL US PEAKS IN JFM. MUCH OF ALASKA IS INDICATED TO HAVE AN ENHANCED LIKELIHOOD OF ABOVE AVERAGE TEMPERATURES DUE TO THE LONG TERM CLIMATE TREND, CONSISTENT WITH THE CFS AND OCN FORECASTS. FORECAST LEADS FROM AMJ 2010 THROUGH DJF 2010 ARE BASED ON THE CONSOLIDATION FORECAST AND ATTRIBUTABLE TO TEMPERATURE TRENDS AND WEAK INTERANNUAL SIGNALS. PRECIPITATION: THE PRECIPITATION OUTLOOKS FOR DJF 2009-10 THROUGH MAM 2010 ARE MAINLY BASED ON THE EXPECTED IMPACTS OF AN EL NINO EVENT, INCLUDING THOSE DEPICTED BY EL NINO COMPOSITES, WHILE THE LONGER LEAD FORECASTS FROM AMJ TO DJF 2010-11 ARE MAINLY BASED ON THE CONSOLIDATION, WHICH USES ONLY STATISTICAL TOOLS AS INPUT AFTER MJJ 2010. THE AREA OF ENHANCED PROBABILITY OF BELOW MEDIAN PRECIPITATION FORECAST FOR THE PACIFIC NORTHWEST FROM DJF 2009 THROUGH MAM 2010 IS A RESULT OF COMPOSITES OF THE EXPECTED IMPACTS OF EL NINO. BELOW MEDIAN PRECIPITATION IS ALSO MOST LIKELY FOR PARTS OF THE MISSISSIPPI AND OHIO VALLEYS FROM DJF 2009-10 THROUGH MAM 2010 LARGELY DUE TO EL NINO. LIKELY ABOVE MEDIAN PRECIPITATION FOR THE GULF COAST AND FLORIDA INTO THE SPRING OF 2010 IS MAINLY A RESULT OF THE EXPECTED IMPACT OF EL NINO BEGINNING WITH DJF 2009, PEAKING IN JFM 2010 AND LIKELY EXTENDING INTO MAM. THE ENHANCED PROBABILITY OF ABOVE MEDIAN PRECIPITATION ACROSS THE ENTIRE SOUTHERN US DURING THE WINTER SEASONS WHICH EXTENDS INTO THE SOUTHERN PLAINS DURING JFM 2010 IS DUE TO EXPECTED EL NINO IMPACTS. DUE TO THE INHERENT NATURALY VARIABILITY AMONG DIFFERENT EL NINO EVENTS, THE SHIFTS IN THE PROBABILITY DISTRIBUTION ACROSS THE SOUTHWEST AND CALIFORNIA IS FAIRLY SMALL. USING THE CONSOLIDATION FORECASTS AS A GUIDE, SIGNALS PRIMARILY DUE TO PRECIPITATION TRENDS ARE INDICATED IN JJA 2010 TO SON 2010. PARTS OF THE PACIFIC NORTHWEST ARE MOST LIKELY TO RECEIVE BELOW MEDIAN PRECIPITATION DURING THE SUMMER OF 2010. A DECADAL PRECIPITATION TREND LEADS TO THE ENHANCED PROBABILITY OF ABOVE MEDIAN PRECIPITATION EAST OF THE CENTRAL ROCKIES. FLORIDA AND PARTS OF THE SOUTHERN ATLANTIC COAST ARE MOST LIKELY TO RECEIVE ABOVE MEDIAN PRECIPITATION FOR PARTICULAR SEASONS FROM JJA TO SON 2010 DUE TO DECADAL TRENDS. IN DJF 2010-11 BELOW MEDIAN PRECIPITATION DUE TO TRENDS RETURNS IN THE SOUTHEAST. NOTE - AREAS OF UNCERTAINTY THAT FORMERLY WERE LABELED CL (CLIMATOLOGICAL PROBABILITIES) ARE NOW LABELED EC (EQUAL CHANCES). FORECASTER: HUUG VAN DEN DOOL 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 THU DEC 17 2009 1971-2000 BASE PERIOD MEANS WERE IMPLEMENTED EFFECTIVE WITH THE MAY 17, 2001 FORECAST RELEASE. $$