PROGNOSTIC DISCUSSION FOR LONG-LEAD SEASONAL OUTLOOKS NWS CLIMATE PREDICTION CENTER CAMP SPRINGS MD 830 AM EDT THU OCT 18 2007 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. 2) TRENDS - APPROXIMATED BY 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). THE OCN TOOL REPRESENTS THE TREND. 3) THE TROPICAL 30-60 DAY OSCILLATION - 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) 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. 6) STATISTICAL FORECAST TOOLS - CANONICAL CORRELATION ANALYSIS (CCA)... AND SCREENING MULTIPLE LINEAR REGRESSION (SMLR). 7) DYNAMICAL FORECAST MODELS... INCLUDING THE NCEP CLIMATE FORECAST SYSTEM (CFS). 8) AN OBJECTIVE CONSOLIDATION (ABBREVIATED CON IN THE TEXT) OF THE OCN... CCA... SMLR 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. LA NINA CONDITIONS WHICH DEVELOPED WITHIN THE PAST FEW MONTHS CONTINUE TO STRENGTHEN. SEA SURFACE TEMPERATURES (SSTS) ARE NOW BELOW AVERAGE THROUGHOUT THE EASTERN EQUATORIAL PACIFIC OCEAN AND ARE NOW BETWEEN 2 AND 3 DEGREES C BELOW NORMAL BETWEEN 120W AND THE SOUTH AMERICAN COAST. SSTS IN THE NINO 3.4 REGION (FROM 5N TO 5S AND 170W TO 120W) ARE CONSIDERED A GOOD INDICATOR OF THE STRENGTH OF A LA NINA. SSTS IN THE NINO 3.4 REGION HAVE DECREASED MARKEDLY IN THE LAST MONTH AND AVERAGED 1.7 DEGREES C BELOW NORMAL IN EARLY OCTOBER. THESE OBSERVATIONS NOW ARE IN LINE WITH WHAT MOST DYNAMICAL AND STATISTICAL MODELS WERE PREDICTING FOR THIS FALL AND WINTER... WHICH INCREASED CONFIDENCE IN THE FORECAST FOR SSTS AND SUPPORTS THE PREDICTION OF AT LEAST WEAK... AND MORE LIKELY... MODERATE LA NINA CONDITIONS IN THE NEXT FEW MONTHS. THE CONSENSUS OF MODEL FORECASTS FOR NINO 3.4 SSTS INDICATE THAT THE CURRENT SST ANOMALIES OF BETWEEN 1 AND 2 DEGREES C BELOW NORMAL WILL PERSIST THROUGH THE REMAINDER OF THE YEAR... AND THEN GRADUALLY DIMINISH IN SPRING 2008. THE TEMPERATURE AND PRECIPITATION OUTLOOK FOR NOVEMBER-DECEMBER-JANUARY (NDJ) 2007-2008 REFLECTS THE LA NINA IMPACTS IN COMBINATION WITH RECENT TRENDS. TEMPERATURES ARE EXPECTED TO AVERAGE ABOVE NORMAL OVER MOST OF THE COUNTRY... PRIMARILY REFLECTING TRENDS... BUT WITH ADDITIONAL CONFIDENCE IN MUCH OF THE SOUTHERN HALF OF THE U.S. WHERE LA NINA ALSO FAVORS ABOVE NORMAL TEMPERATURES. LA NINA CONDITIONS ARE EXPECTED TO LESSEN THE IMPACT OF RECENT TRENDS TOWARD ABOVE NORMAL TEMPERATURES OVER MUCH OF THE NORTHERN HALF OF THE COUNTRY FROM THE PACIFIC NORTHWEST TO THE GREAT LAKES. WHEN THE INFLUENCE OF LA NINA AND TRENDS ARE TAKEN TOGETHER... ABOVE NORMAL TEMPERATURES ARE ONLY SLIGHTLY FAVORED OVER MUCH OF THE NORTH CENTRAL STATES... THE CENTRAL GREAT PLAINS... AND CENTRAL ROCKIES. TEMPERATURES IN THE PACIFIC NORTHWEST... NORTHERN ROCKIES AND NORTHERN GREAT PLAINS ARE EXPECTED TO BE COOLER THAN THE AVERAGE OF RECENT YEARS AND SEASONAL MEANS SHOULD BE MORE IN LINE WITH THOSE EXPECTED IN THE 1971-2000 CLIMATE BASE PERIOD. THE PRECIPITATION OUTLOOK FOR NDJ 2007-08 FAVORS ABOVE MEDIAN PRECIPITATION AMOUNTS IN PARTS OF THE PACIFIC NORTHWEST AND NORTHERN ROCKIES. BELOW MEDIAN PRECIPITATION AMOUNTS ARE EXPECTED IN THE SOUTHWEST... PARTS OF TEXAS... ALONG THE GULF COAST AND THROUGHOUT MUCH OF THE SOUTHEASTERN U.S. INCLUDING FLORIDA. THESE PRECIPITATION SIGNALS ARE THE EXPECTED RESPONSE TO A MODERATE LA NINA. 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 SEA SURFACE TEMPERATURES (SSTS) ARE SUBSTANTIALLY BELOW AVERAGE IN THE EQUATORIAL PACIFIC FROM THE SOUTH AMERICAN COAST TO JUST EAST OF THE DATELINE. SST ANOMALIES ARE BETWEEN -2 AND -3 C FROM 120W EASTWARD... WHILE TEMPERATURES IN THE CENTRAL EQUATORIAL PACIFIC ARE MOSTLY BETWEEN .5 AND 1.5 DEGREES C BELOW NORMAL. SSTS IN THE NINO 3.4 AND NINO 4 REGIONS HAVE DECREASED RAPIDLY BETWEEN MID-SEPTEMBER AND MID-OCTOBER... WHILE THE NINO 1+2 AND NINO 3 REGIONS MAINTAINED SUBSTANTIALLY BELOW NORMAL SSTS OVER THE PAST 30-DAYS. OCEAN TEMPERATURES IN THE UPPER 200 M HAVE REMAIN WELL BELOW NORMAL AND THE UPPER OCEAN HEAT CONTENT (THE AVERAGE TEMPERATURE IN THE UPPER 300 METERS OF THE OCEAN) CONTINUES TO BE BELOW AVERAGE... LENDING CONFIDENCE THAT BELOW NORMAL OCEAN TEMPERATURES WILL PERSIST AT AND NEAR THE SURFACE FOR THE NEXT FEW MONTHS AT LEAST. ANOMALIES IN OUTGOING LONGWAVE RADIATION SHOW SUPRESSED CONVECTION OVER MUCH OF THE EQUATORIAL PACIFIC... ESPECIALLY NEAR THE DATELINE... AND LOW LEVEL EASTERLY WINDS ARE STRONGER THAN NORMAL OVER THE TROPICAL PACIFIC. THESE ATMOSPHERIC CIRCULATION ANOMALIES ARE CONSISTENT WITH LA NINA CONDITIONS. PROGNOSTIC DISCUSSION OF SST FORECASTS THERE IS CONSENSUS AMONG SST PREDICTION METHODS RUN AT CPC... AS WELL AS MANY RUN AT OTHER CENTERS... THAT NINO 3.4 SSTS WILL REMAIN BETWEEN 1 AND 1.5 C BELOW NORMAL THROUGH THE REMAINDER OF THE YEAR AND INTO EARLY 2008. THE CFS INDICATES SST ANOMALIES IN THE NINO 3.4 REGION OF AROUND -1.8 C WHILE THE STATISTICAL TOOLS... THE MARKOV MODEL... CCA... AND CONSTRUCTED ANALOG PREDICT SST ANOMALIES OF BETWEEN -1.0 AND -1.5 C. A CONSOLIDATION FORECAST BASED ON ALL FOUR LOCALLY GENERATED TOOLS PREDICTS GREATEST ANOMALIES OF ABOUT -1.4 C IN THE NDJ SEASON... DIMINISHING TO ABOUT -1.0 C BY JFM 2008 AND DIMINISHING TO ZERO BY JJA 2008. CONFIDENCE THAT THE NINO 3.4 SSTS WILL REMAIN BELOW THE -.5 C THRESHOLD ASSOCIATED WITH LA NINA CONDITIONS THROUGH JFM 2008 IS QUITE HIGH... ESTIMATED AT 90% BY THE CONSOLIDATION METHOD. PROGNOSTIC TOOLS USED FOR U.S. TEMPERATURE AND PRECIPITATION OUTLOOKS THE TEMPERATURE OUTLOOK FOR ALL LEAD TIMES ARE BASED HEAVILY ON THE CONSOLIDATION (CON) TOOL... WHICH IS A SKILL-WEIGHTED OBJECTIVE BLEND OF CFS... CCA... SMLR AND OCN. THE TEMPERATURE OUTLOOKS FOR NDJ 2007-2008 THROUGH MAM 2008 ARE ALSO INFLUENCED BY TREND-ADJUSTED COMPOSITES BASED ON MODERATE AND STRONG LA NINA CONDITIONS. PRECIPITATION OUTLOOKS FOR NDJ 2007-2008 THROUGH MAM 2008 ARE DERIVED ALMOST ENTIRELY FROM COMPOSITES OF MODERATE AND STRONG LA NINAS... WITH PROBABILITIES ADJUSTED TO REFLECT THE EXPECTED INTENSITY OF THE CURRENT LA NINA CONDITIONS. THE CON IS NOT AVAILABLE FOR ALASKA... SO THE FORECAST THERE IS BASED LARGELY ON ANALYSIS OF THE CFS WITH CONSIDERATION OF THE OCN... CCA AND SMLR. PRECIPITATION OUTLOOKS FOR AMJ 2008 AND BEYOND REFLECT WEAK SIGNALS FROM LONG TERM TRENDS. PROGNOSTIC DISCUSSION OF OUTLOOKS - NDJ 2007 TO NDJ 2008 TEMPERATURE: THE TEMPERATURE OUTLOOK FOR NDJ 2007-08 CALLS FOR ENHANCED CHANCES OF ABOVE NORMAL TEMPERATURES FOR LARGE PARTS OF THE CONUS. THIS HAS BROAD BASED SUPPORT AMONG TOOLS BOTH RUN LOCALLY AS REFLECTED IN THE CONSOLIDATION FORECASTS AND ALSO FROM NUMERICAL MODELS RUN AT OTHER CENTERS AS REFLECT IN THE IRI MULTI-MODEL ENSEMBLE FORECAST. MODIFICATIONS THAT WERE MADE ON THE BASIS OF LA NINA COMPOSITES INCLUDE AN INCREASE IN CONFIDENCE FOR ABOVE NORMAL TEMPERATURES FROM THE SOUTHERN GREAT PLAINS AND TEXAS TO THE WESTERN GULF STATES... AND A DECREASE IN THE CHANCES OF TREND-RELATED ABOVE NORMAL TEMPERATURES FOR THE NORTHERN GREAT PLAINS... THE NORTHERN ROCKIES... THE PACIFIC NORTHWEST... AND NORTHERN GREAT BASIN. THE SEASONAL OUTLOOKS FOR DJF 2007-08 THROUGH FMA 2008 LARGELY REFLECT THIS SAME COOL SEASON TEMPERATURE PATTERN... WITH TREND ADJUSTED LA NINA COMPOSITES FAVORING NEAR NORMAL TEMPERATURES IN PARTS OF THE NORTHERN GREAT PLAINS AND UPPER MISSISSIPPI VALLEY IN JFM. THE TREND DOMINATES THE TEMPERATURE CONSOLIDATION FORECAST THROUGH THE REMAINING OUTLOOKS. PRECIPITATION: THE PRECIPITATION OUTLOOK FOR NDJ 2007-08 CALLS FOR ELEVATED CHANCES OF ABOVE MEDIAN PRECIPITATION AMOUNTS IN THE PACIFIC NORTHWEST AND FOR ENHANCED CHANCES OF BELOW MEDIAN PRECIPITATION AMOUNTS FOR MUCH OF THE SOUTHERN THIRD OF THE CONUS. BOTH OF THESE FEATURES ARE FAVORED BY TREND-ADJUSTED LA NINA COMPOSITES AND THE CONSOLIDATION TOOL. FROM DJF 2007-08 TO FMA 2008... BELOW MEDIAN PRECIPITATION IS EXPECTED ACROSS MOST OF THE SOUTHERN UNITED STATES WITH GREATER PROBABILITIES FOR THE SOUTHWEST AND IN SOUTHEASTERN STATES... SUPPORTED BY BOTH THE CONSOLIDATION AND BY TREND-ADJUSTED COMPOSITES BASED ON LA NINA CONDITIONS. AN ENHANCED LIKELIHOOD OF ABOVE MEDIAN PRECIPITATION IS SHOWN FOR PARTS OF THE PACIFIC NORTHWEST THROUGH FMA 2008 AND IS ALSO CONSISTENT WITH LA NINA CONDITIONS. ABOVE MEDIAN PRECIPITATION AMOUNTS ARE ALSO FAVORED IN THE OHIO AND TENNESSEE VALLEYS FOR DJF 2007-08 AND JFM 2008... ALSO RELATED TO LA NINA... AS EVIDENT IN TREND-ADJUSTED COMPOSITES. FORECASTS FOR LEAD TIMES AMJ 2008 AND BEYOND ARE BASED ON LONG TERM TRENDS AND THE CONSOLIDATION TOOL... WITH THE LIKELIHOOD OF ABOVE NORMAL PRECIPITATION INCREASED ALONG PARTS OF THE GULF COAST DURING LATE SUMMER AND EARLY FALL. BELOW MEDIAN PRECIPITATION AMOUNTS ARE EXPECTED FOR THE PACIFIC NORTHWEST FROM JJA THROUGH SON 2008... AND ABOVE MEDIAN PRECIPITATION AMOUNTS ARE FAVORED IN PARTS OF THE NORTHERN GREAT PLAINS IN SON AND OND 2008. NOTE - AREAS OF UNCERTAINTY THAT FORMERLY WERE LABELED CL (CLIMATOLOGICAL PROBABILITIES) ARE NOW LABELED EC (EQUAL CHANCES). FORECASTER: DAVID UNGER 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 NOV 15 2007 1971-2000 BASE PERIOD MEANS WERE IMPLEMENTED EFFECTIVE WITH THE MAY 17, 2001 FORECAST RELEASE. $$