538 FXUS05 KWBC 251230 PMD90D PROGNOSTIC DISCUSSION FOR LONG-LEAD SEASONAL OUTLOOKS NWS CLIMATE PREDICTION CENTER CAMP SPRINGS MD 830 AM EDT THU SEP 18 2008 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 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. ENSO-NEUTRAL CONDITIONS CONTINUED DURING AUGUST 2008, AS GENERALLY NEAR AVERAGE SEA SURFACE TEMPERATURES (SSTS) WERE OBSERVED ACROSS THE EQUATORIAL PACIFIC OCEAN. ALTHOUGH ENSO-NEUTRAL CONDITIONS HAVE BEEN IN PLACE SINCE JUNE 2008, THE ATMOSPHERIC CIRCULATION OVER THE WESTERN AND CENTRAL TROPICAL PACIFIC CONTINUES TO REFLECT LINGERING ASPECTS OF LA NINA. THERE IS EXCELLENT AGREEMENT IN THE FORECAST FOR NINO 3.4 SST ANOMALIES IN THE NEXT FEW MONTHS. A CONSENSUS OF THE FORECASTS MAINTAINS ENSO NEUTRAL CONDITIONS WELL INTO NEXT YEAR. THEREFORE THE SUITE OF TEMPERATURE AND PRECIPITATION FORECASTS DOES NOT USE COMPOSITES BASED ON EL NINO OR LA NINA. THE TEMPERATURE OUTLOOK FOR OND 2008 CALLS FOR ABOVE NORMAL TEMPERATURES ACROSS MUCH OF THE WESTERN HALF OF THE CONUS, WITH THE EXCEPTION OF ALONG THE WEST COAST AND IN SOUTHERN ALASKA. THESE EXPECTED AREAS OF ABOVE AVERAGE TEMPERATURES ARE DUE PRIMARILY TO RECENT TEMPERATURE TRENDS AND FOLLOW CLOSELY THE OBJECTIVE CONSOLIDATION FORECAST, WHICH INCLUDES THE STATISTICAL FORECAST TOOLS AND THE CFS FORECAST. THERE IS AN ENHANCED LIKELIHOOD OF BELOW MEDIAN PRECIPITATION FOR OND 2008 IN THE SOUTHWEST AS INDICATED BY THE OBJECTIVE CONSOLIDATION DUE TO RECENT TRENDS. 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 ENSO-NEUTRAL CONDITIONS CONTINUED DURING AUGUST 2008, AS RECENT INCREASES IN SEA SURFACE TEMPERATURES (SSTS) ABATED ACROSS THE EQUATORIAL PACIFIC OCEAN. ABOVE-AVERAGE SSTS IN THE EAST-CENTRAL AND EASTERN PACIFIC DIMINISHED, WHILE BELOW-AVERAGE SSTS IN THE CENTRAL PACIFIC STRENGTHENED SLIGHTLY. FROM WEST TO EAST, THE LATEST WEEKLY SST INDEX VALUES RANGE FROM -0.4C IN THE NINO-4 REGION TO +0.7C IN THE NINO 1+2 REGION. THE SUBSURFACE OCEANIC HEAT CONTENT (AVERAGE TEMPERATURES IN THE UPPER 300M OF THE OCEAN) ALSO DECREASED IN RESPONSE TO THE EMERGENCE OF NEGATIVE TEMPERATURE ANOMALIES AT THERMOCLINE DEPTH IN THE EAST-CENTRAL PACIFIC. ALTHOUGH ENSO-NEUTRAL CONDITIONS HAVE BEEN IN PLACE SINCE JUNE 2008, THE ATMOSPHERIC CIRCULATION OVER THE WESTERN AND CENTRAL TROPICAL PACIFIC CONTINUES TO REFLECT LINGERING ASPECTS OF LA NINA. ENHANCED LOW-LEVEL EASTERLY WINDS AND UPPER-LEVEL WESTERLY WINDS PERSIST IN THIS REGION, WHILE CONVECTION REMAINS GENERALLY SUPPRESSED OVER THE CENTRAL PACIFIC. DESPITE THIS LINGERING LA NINA SIGNAL IN THE ATMOSPHERE, THE OVERALL ATMOSPHERIC AND OCEANIC SYSTEM IS CONSISTENT WITH ENSO-NEUTRAL CONDITIONS. PROGNOSTIC DISCUSSION OF SST FORECASTS MOST DYNAMICAL AND STATISTICAL SST FORECASTS FOR THE NINO 3.4 REGION PREDICT SSTS IN THE RANGE BETWEEN -0.5 AND +0.5 C, INDICATING ENSO-NEUTRAL CONDITIONS, THROUGH AUTUMN AND INTO NEXT YEAR. ALL NCEP SST FORECASTS MAINTAIN SLIGHTLY NEGATIVE NINO 3.4 SST ANOMALIES THROUGH 2008 INTO 2009. A CONSOLIDATION OF NCEP FORECASTS SUGGESTS THAT NINO 3.4 SST ANOMALIES ARE MOST LIKELY TO REMAIN SLIGHTLY BELOW ZERO THROUGH THE SPRING OF 2009. CONSIDERING CURRENT OBSERVATIONS AND SST FORECASTS FROM STATISTICAL AND DYNAMICAL MODELS FROM NCEP AND FROM OTHER CENTERS NOT INCLUDED IN THE CONSOLIDATION FORECAST, ENSO NEUTRAL CONDITIONS ARE CONSIDERED MOST LIKELY THROUGH THE END OF THE YEAR WITH NINO 3.4 SST ANOMALIES EXPECTED TO BE WITHIN ONE HALF OF ONE DEGREE CELSIUS OF ZERO. ATMOSPHERIC CONDITIONS RELATED TO LA NINA OFTEN PERSIST FOR A FEW MONTHS AFTER SSTS RETURN TO ENSO NEUTRAL CONDITIONS - AND THIS YEAR IS NO EXCEPTION. RESIDUAL LA NINA ATMOSPHERIC CONDITIONS MAY SLIGHTLY ENHANCE TROPICAL ACTIVITY IN THE ATLANTIC AND SLIGHTLY SUPPRESS TROPICAL ACTIVITY IN THE EASTERN PACIFIC IN THE FALL.(SEE THE NOAA 2008 HURRICANE SEASON OUTLOOK DISCUSSION FOR MORE INFORMATION). PROGNOSTIC TOOLS USED FOR U.S. TEMPERATURE AND PRECIPITATION OUTLOOKS THE TEMPERATURE AND PRECIPITATION OUTLOOKS FOR ALL LEAD TIMES ARE BASED ON THE CONSOLIDATION (CON), A SKILL-WEIGHTED AND CALIBRATED OBJECTIVE BLEND OF THE CFS, SMLR, OCN, AND ECCA FORECAST TOOLS. OTHER TOOLS - IRI ECPC AND CAS -ARE CONSIDERED AND USED FOR EXPERT ADJUSTMENT OF THE FORECAST. THE CON FORECAST IS NOT AVAILABLE FOR ALASKA, SO THE FORECAST THERE IS BASED ON THE FORECASTERS COMBINING OCN, SMLR AND THE CFS FORECASTS. THE ENSO STATE IS NOT EXPECTED TO HAVE AN IMPACT ON THE COMING SEASONAL TEMPERATURE AND PRECIPITATION OUTLOOKS. THE TEMPERATURE AND PRECIPITATION OUTLOOKS FROM OND 2008 TO OND 2009 CLOSELY FOLLOW THE CON FORECAST - THIS IS MORE OBVIOUS FOR TEMPERATURE THAN FOR PRECIPITATION BECAUSE THE LATTER HAS LESS SKILL. THE CFS FORECAST IS ONLY AVAILABLE AND PART OF THE CONSOLIDATION THROUGH MAM 2009. PROGNOSTIC DISCUSSION OF OUTLOOKS - OND 2008 TO OND 2009 TEMPERATURE: THE OUTLOOK FOR OND 2008 INDICATES ENHANCED PROBABILITIES OF ABOVE AVERAGE TEMPERATURES FOR SOUTHERN ALASKA AND MUCH OF THE WESTERN HALF OF THE NATION... WITH THE EXCEPTION OF ALONG THE WEST COAST. WITH CURRENT ENSO NEUTRAL CONDITIONS IN PLACE...THE EXPECTATIONS FOR ABOVE NORMAL TEMPERATURES DURING THE OND 2008 SEASON ARE LARGELY DUE TO RECENT TEMPERATURE TRENDS. TEMPERATURE FORECASTS AFTER OND 2008 CLOSELY FOLLOW THE CONSOLIDATION FORECAST DERIVED FROM THE CFS, OCN, ECCA AND SMLR. CURRENT ENSO NEUTRAL CONDITIONS AND UNCERTAINTY IN THE FUTURE ENSO STATE MEAN THAT ALL SEASONAL TEMPERATURE FORECASTS ARE LARGELY IMPACTED BY TEMPERATURE TRENDS. THE AREA OF ENHANCED CHANCES OF ABOVE AVERAGE TEMPERATURES EXPANDS TO INCLUDE MORE OF THE U.S. FROM NDJ 2008-2009 THROUGH JFM 2009... WITH THE EXCEPTION OF ALONG THE CALIFORNIA COAST AND PARTS OF THE EAST COAST. THE AREAS OF GREATER THAN CLIMATOLOGICAL PROBABILITIES OF ABOVE NORMAL TEMPERATURES DECREASE SUBSTANTIALLY THROUGH THE NEXT FEW THREE-MONTH PERIODS BEFORE EXPANDING TO COVER MOST OF THE WESTERN AND EASTERN U.S. DURING THE JAS 2009 OUTLOOK. THE OUTLOOKS FOR ALASKA ARE DERIVED MAINLY FROM THE RECENT TEMPERATURE TRENDS WITH SECONDARY SUPPORT FROM OTHER TOOLS. PRECIPITATION: ELEVATED PROBABILITIES IN THE OND 2008 OUTLOOK FOR BELOW MEDIAN PRECIPITATION FOR THE SOUTHWESTERN U.S. ARE DERIVED FROM THE CONSOLIDATION FORECAST... WITH STRONG SUPPORT FROM THE CFS AND THE ECCA. THE CONSOLIDATION ALSO SUGGESTS BELOW MEDIAN PRECIPITATION IN PARTS OF THE SOUTHEAST... BUT THIS SIGNAL WAS NOT INCLUDED IN THE OFFICIAL FORECAST DUE TO THE POTENTIAL FOR IMPACTS FROM TROPICAL CYCLONES STEMMING FROM THE ACTIVE HURRICANE SEASON. THE ABOVE MEDIAN PRECIPITATION FORECAST FOR COASTAL AREAS IN THE SOUTHEAST IN JAS AND ASO 2009 ARE RELATED TO INCREASED TROPICAL ACTIVITY DURING RECENT YEARS. AREAS OF BELOW MEDIAN PRECIPITATION ARE FORECAST FOR PARTS OF THE DESERT SOUTHWEST FROM NDJ 2008-2009 TO JFM 2009 AND FOR MUCH OF THE SOUTHEAST FROM NDJ 2008-2009 TO MAM 2009 RESULTING FROM RECENT PREDICTABLE PRECIPITATION TRENDS AS INDICATED BY THE CONSOLIDATION. AREAS OF INCREASED PROBABILITY FOR ABOVE MEDIAN PRECIPITATION CENTERED AROUND THE TEXAS PANHANDLE FOR DJF 2008-2009 AND JFM 2009 ALSO REPRESENT RECENT TRENDS AS INDICATED BY THE CONSOLIDATION. THE PRECIPITATION OUTLOOK OVER ALASKA FOR ALL SEASONS IS LEFT AT CLIMATOLOGICAL PROBABILITIES, WITH NO STRONG TRENDS IN PRECIPITATION EVIDENT DURING ANY SEASON. NOTE - AREAS OF UNCERTAINTY THAT FORMERLY WERE LABELED CL (CLIMATOLOGICAL PROBABILITIES) ARE NOW LABELED EC (EQUAL CHANCES). FORECASTER: MIKE HALPERT 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 OCT 16 2008 1971-2000 BASE PERIOD MEANS WERE IMPLEMENTED EFFECTIVE WITH THE MAY 17, 2001 FORECAST RELEASE. $$