PROGNOSTIC DISCUSSION FOR LONG-LEAD SEASONAL OUTLOOKS NWS CLIMATE PREDICTION CENTER CAMP SPRINGS MD 830 AM EDT THU OCT 15 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. THE MAIN FORECAST TOOLS ARE AS FOLLOWS: 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 WEAK EL NINO CONDITIONS ARE EXPECTED TO STRENGTHEN AND PERSIST INTO THE 2009-10 NORTHERN HEMISPHERE WINTER. THE LIKELIHOOD OF A CONTINUING EL NINO EVENT INFLUENCES THE TEMPERATURE AND PRECIPITATION OUTLOOKS FOR OND 2009 THROUGH MAM 2010, MAINLY VIA COMPOSITES FOR WEAK-TO-MODERATE EVENTS. THE IMPACT OF EL NINO ON THE CLIMATE OVER NORTH AMERICA IS EXPECTED TO BE GREATEST DURING THE WINTER SEASONS. A MODERATE STRENGTH EL NINO IS MOST LIKELY DURING THE WINTER. 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 NDJ 2009-10 INDICATES AN ENHANCED LIKELIHOOD OF ABOVE AVERAGE TEMPERATURES FOR MUCH OF THE WESTERN HALF OF THE CONUS AND ALASKA. 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 ACCUMULATED PRECIPITATION IS MOST LIKELY DURING OND 2009 FOR PARTS OF THE PACIFIC NORTHWEST. ABOVE MEDIAN PRECIPITATION AMOUNTS ARE MOST LIKELY ALONG THE GULF COAST FROM TEXAS TO FLORIDA, AND IN CALIFORNIA, AND NORTHERN SECTIONS OF ALASKA. WHERE THE LIKELIHOOD OF ABOVE OR BELOW MEDIAN SEASONAL PRECIPITATION IS SIMILAR TO THE CLIMATOLOGY, 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 FIVE-DAY MEAN SEA SURFACE TEMPERATURE (SST) ANOMALIES HAVE SLOWLY WARMED OVER THE FIRST HALF OF OCTOBER, AND EXCEED +0.5 CELSIUS ACROSS MOST OF THE EQUATORIAL PACIFIC OCEAN AND ARE FROM +1 TO +1.5 CELSIUS NEAR THE DATE LINE AND IN PARTS OF THE THE EASTERN HALF OF THE BASIN. OUTGOING LONGWAVE RADIATION ANOMALIES INDICATE THAT CONVECTION IS SUPPRESSED OVER THE MARITIME CONTINENT AND SLIGHTLY ENHANCED ACROSS THE WESTERN PACIFIC. TRADE WINDS IN THE EASTERN PART OF THE BASIN WEAKENED DURING THIS PERIOD. SUBSURFACE HEAT CONTENT IS GENERALLY ABOVE NORMAL IN THE UPPER 200 METERS OF THE TROPICAL PACIFIC OCEAN WITH TEMPERATURE ANOMALIES EXCEEDING +2 CELSIUS AT THERMOCLINE DEPTH BETWEEN 170E AND 150W. 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 JANUARY 2010. PROGNOSTIC DISCUSSION OF SST FORECASTS THE CURRENT MEAN ENSEMBLE CFS FORECAST INDICATES SST ANOMALIES IN THE NINO 3.4 REGION PEAKING NEAR +1.5 CELSIUS BEFORE THE END OF 2009, WITH THE ENSEMBLE SPREAD RANGING FROM +1 TO ABOUT +2 CELSIUS, THUS CALLING FOR MODERATE TO STRONG EL NINO CONDITIONS BY EARLY NORTHERN HEMISPHERE WINTER. THIS FORECAST IS AMONG THE WARMEST IN THE IRI MULTI-MODEL ENSEMBLE PLUME. THE CFS SST FORECAST HAS RECENTLY BEGUN TO PREDICT A SLIGHTLY STRONGER EVENT THAN IT HAS IN RECENT WEEKS. 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 CONSTRUCTED ANALOG MODEL PREDICTS THE LARGEST POSITIVE ANOMALY, SLIGHTLY GREATER THAN +1.5 DEGREES CELSIUS. THE CPC CONSOLIDATION OF NINO 3.4 SST TEMPERATURE ANOMALY FORECASTS INDICATES THAT THE CURRENT EL NINO WILL LIKELY WEAKEN AND END BY AMJ 2010. 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 OND 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. THE CFS FORECAST ALSO INDICATES MORE COLD TEMPERATURES IN THE CENTRAL AND EASTERN CONUS EARLY IN THE FORECAST PERIOD. THE TEMPERATURE OCN, OR TREND, HAS BEEN CHANGING OVER THE PAST DECADE. IN THE 90S, THE OCN'S STRONGEST SIGNAL (FOR WARMTH) WAS DURING JFM. THIS HAS SHIFTED TO THE LATE FALL, AND HAS WEAKENED IN THE WINTER. THE LARGEST PART OF THE TREND SIGNAL FOR WARMTH CONTINUES TO RESIDE IN THE SOUTHWEST CONUS. PROGNOSTIC DISCUSSION OF OUTLOOKS - NDJ 2009 TO NDJ 2010 TEMPERATURE: THE TEMPERATURE OUTLOOKS FOR NDJ 2009 THROUGH NDJ 2010 INDICATE THAT THREE-MONTH MEAN TEMPERATURES ARE MOST LIKELY TO BE IN THE ABOVE NORMAL CATEGORY FOR MUCH OF THE WESTERN US 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 NDJ THROUGH MAM. THE STATISTICAL CONSOLIDATION DOES NOT ACCOUNT FOR INCREASES IN THE SKILL OF FORECASTS THAT INCLUDE AN ENSO SIGNAL. BEGINNING IN NDJ 2009 AND ONTINUING TO SOME DEGREE THROUGHOUT THE NEXT 12 MONTHS, ABOVE NORMAL MEAN TEMPERATURES ARE MOST LIKELY IN THE SECTIONS OF THE US SOUTHWEST, MAINLY AS A RESULT OF THE LOCAL TEMPERATURE TREND. 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 NDJ 2009 TO FMA 2010 AS A RESULT OF EL NINO. THE LIKELIHOOD OF ABOVE AVERAGE TEMPERATURES INCREASES IN THE NORTH-CENTRAL US FROM NDJ 2009 THROUGH FMA 2010. 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 MAM 2010 THROUGH NDJ 2010 ARE BASED ON THE CONSOLIDATION FORECAST AND ATTRIBUTABLE TO TEMPERATURE TRENDS AND WEAK INTERANNUAL SIGNALS. PRECIPITATION: THE PRECIPITATION OUTLOOKS FOR OND 2009 THROUGH FMA 2010 ARE MAINLY BASED ON THE EXPECTED IMPACTS OF A PROBABLE EL NINO EVENT, INCLUDING THOSE DEPICTED BY EL NINO COMPOSITES, WHILE THE LONGER LEAD FORECASTS FROM AMJ TO NDJ 2010 ARE MAINLY BASED ON THE CONSOLIDATION, WHICH USES ONLY STATISTICAL TOOLS AS INPUT AFTER AMJ 2010. THE AREA OF ENHANCED PROBABILITY OF BELOW MEDIAN PRECIPITATION FORECAST FOR THE PACIFIC NORTHWEST FROM NDJ 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 LIKELY IMPACT OF EL NINO BEGINNING WITH NDJ 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 UNCERTAINTY IN THE POTENTIAL STRENGTH OF THE EL NINO, AND 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 TROPICAL PRECIPITATION. NOTE - AREAS OF UNCERTAINTY THAT FORMERLY WERE LABELED CL (CLIMATOLOGICAL PROBABILITIES) ARE NOW LABELED EC (EQUAL CHANCES). FORECASTER: ED O'LENIC