PROGNOSTIC DISCUSSION FOR LONG-LEAD OUTLOOKS CLIMATE PREDICTION CENTER NCEP NATIONAL WEATHER SERVICE WASHINGTON DC 3 PM EDT THURSDAY SEPTEMBER 13 2001 BASIS AND SUMMARY OF THE CURRENT LONG-LEAD OUTLOOK . . . . . . . . THESE OUTLOOKS PRIMARILY REFLECT THE EXPECTED U.S. CLIMATE ANOMALIES FOR ENSO- NEUTRAL CONDITIONS ... AND THE LONG-TERM TREND AS ESTIMATED BY OCN. EQUATORIAL PACIFIC SSTS ARE NOW SLIGHTLY ABOVE NORMAL IN THE WEST AND CENTRAL PACIFIC AND SLIGHTLY BELOW NORMAL NEAR SOUTH AMERICA. MOST STATISTICAL AND DYNAMIC PREDICTIONS OF NINO 3.4 SSTS INDICATE ANOMALIES VERY NEAR ZERO THROUGHOUT THE UPCOMING COOL SEASON WITH SLIGHT WARM EPISODE (EL NINO) CONDITIONS BY LATE IN THE SPRING OR EARLY IN THE SUMMER OF 2002. WHILE IT IS LIKELY THAT EQUATORIAL PACIFIC SSTS NEAR THE DATELINE WILL BE ABOVE AVERAGE ... THE ANOMALIES ARE EXPECTED TO BE WEAK AND NOT LIKELY TO PRODUCE THE LARGE-SCALE ATMOSPHERIC EFFECTS ASSOCIATED WITH STRONG EL NINO EVENTS THIS COOL SEASON. THE ABSENCE OF SIGNIFICANT ENSO-RELATED INFLUENCES SUGGESTS THE UPCOMING COOL SEASON MAY BE MARKED BY SIGNIFICANT VARIABILITY. CURRENT ATMOSPHERIC AND OCEANIC CONDITIONS NEAR-NORMAL ATMOSPHERIC AND OCEANIC CONDITIONS CONTINUE TO PREVAIL IN THE TROPICAL PACIFIC IN AUGUST. SST ANOMALIES ALONG THE EQUATOR CURRENTLY ARE OVER +1.0 DEG C IN THE CENTRAL PACIFIC AND ARE AROUND -1.O DEG IN THE EASTERN PACIFC. THE ABOVE NORMAL OCEAN TEMPERATURE EXTEND FROM THE SURFACE OR NEAR THE SURFACE TO OVER 200 M DEPTH OVER MOST OF THE CENTRAL PACIFIC OCEAN AND TO 100 M DEPTH AS FAR EAST AS 130 W. ATMOSPHERIC CIRCULATION IN THE TROPICAL PACIFIC HAS BEEN VERY CLOSE TO NORMAL FOR A NUMBER OF MONTHS NOW. . . . . . . . . PROGNOSTIC DISCUSSION OF SST FORECASTS WEAK WARM ENSO CONDITIONS ARE PREDICTED TO SLOWLY DEVELOP OVER THE NEXT SEVERAL SEASONS. MOST DYNAMIC MODELS (NCEP - ECMWF - SCRIPPS) GRADUALLY INCREASE NINO 3.4 SSTS BUT ONLY SLIGHTLY BY YEARS END ... BUT ECMWF AND SCRIPPS INCREASE THE AREAL COVERAGE OF ABOVE NORMAL TEMPERATURES IN THE EQUATORIAL PACIFIC. ON THE OTHER HAND ... THE CONSTRUCTED ANALOG AND INVERSE MODEL PREDICT NEUTRAL OR COOL NINO 3.4 SSTS FOR THIS COOL SEASON ALTHOUGH THE CCA PREDICTION IS FOR ABOVE NORMAL SSTS. BY NEXT SPRING THE NCEP MODEL AND CCA MODELS ARE PREDICTING ABOVE NORMAL SSTS FOR NINO 3.4. A CONSOLIDATION OF THREE NCEP TOOLS BASED ON THEIR PAST PERFORMANCE INDICATES NEAR NORMAL CONDITIONS WILL PREVAIL THROUGH THE WINTER WITH GRADUALLY INCREASING ANOMALIES THAT REACH AROUND +0.5 DEGREES C BY LATE NEXT SPRING. CONSIDERING THAT TEMPERATURES ANOMALIES ARE ALREADY POSITIVE NINO 3.4 SEA SURFACE TEMPERATURES ARE EXPECTED TO REMAIN POSITIVE FOR THE REMAINDER OF THE YEAR - GRADUALLY INCREASING TO MARGINALLY WARM ENSO CONDITIONS BY LATE NEXT SPRING. PROGNOSTIC TOOLS USED FOR U.S. TEMPERATURE AND PRECIPITATION OUTLOOK THE STATISTICAL TOOLS ... CCA ... OCN AND SMLR ... WERE CONSULTED AT ALL LEAD TIMES. THE CONSTRUCTED ANALOG SOIL MOISTURE-BASED FORECAST TOOL (CAS) WAS USED SPARINGLY SINCE WE ARE ENTERING THE COOL SEASON. BECAUSE THE INITIAL ENSO STATE IS NEAR ZERO AND IS FORECAST TO BE WEAK - THE NCEP COUPLED MODEL WAS CONSIDERED ONLY WHERE IT AGREED WITH A CONSENSUS OF OTHER GENERAL CIRCULATION MODELS RUN AT OTHER CENTERS FOR CLIMATE PREDICTION. . . . . . . . . PROGNOSTIC DISCUSSION OF OUTLOOKS - OND 2001 TO OND 2002 TEMPERATURE: MOST FORECAST TOOLS INDICATE WARMER-THAN-NORMAL TEMPERATURES FOR OND 2001 THROUGH DJF 2001 IN THE SOUTHWEST U.S. ... WITH THE EXCEPTION OF THE CMP. DRY INITIAL SOIL MOISTURE CONDITIONS IN WEST TEXAS EXTEND THIS AREA OF ABOVE NORMAL TEMPERATURES INTO SOUTHWESTERN OF TEXAS FOR OND. BELOW NORMAL TEMPERATURES FORECAST FOR WESTERN ALASKA FOR OND AND NDJ ARE FROM CCA. WITH LITTLE OR NO ENSO FORCING ... THE PRIMARY FACTOR INFLUENCING THE SEASONAL CLIMATE ANOMALIES OVER THE EASTERN U.S. THIS WINTER WILL BE THE PHASE OF THE ARCTIC OSCILLATION (AO). THE AO IS NOT PREDICTABLE BEYOND THE LIMITS OF WEATHER PREDICTION MODELS BUT RECENT TRENDS SUGGEST THAT THE SEASONAL FREQUENCY OF THE AO NEGATIVE PHASE IS GREATER THAN IT WAS IN THE EARLY AND MID 1990S. SINCE THE NEGATIVE AO PHASE IS ASSOCIATED WITH COOLER THAN NORMAL CONDITIONS THROUGHOUT THE EAST ... THE AO TREND COUNTERACTS RECENT TRENDS TOWARD WARMER-THAN-NORMAL WINTER TEMPERATURES OVER MUCH OF THE EASTERN U.S.. ALTHOUGH THE CENTRAL PACIFIC EQUATORIAL SSTS ARE EXPECTED TO BE SOMEWHAT ABOVE NORMAL DURING THE COOL SEASON ... THIS IS NOT EXPECTED TO HAVE A GREAT INFLUENCE ON U.S. TEMPERATURES FOR MUCH OF THE COOL SEASON. IN SUCH NEUTRAL ENSO CONDITIONS TEMPERATURES OVER MUCH OF THE CENTRAL AND EASTERN U.S. ARE USUALLY BELOW NORMAL ... WHICH ALSO COUNTERACTS RECENT OVERALL TRENDS. THE AO HAS LITTLE INFLUENCE IN THE WESTERN U.S. AND THEREFORE TEMPERATURE TRENDS ACCOUNT FOR THE LARGE AREA OF ABOVE NORMAL TEMPERATURES PREDICTED IN THE WESTERN U.S. FROM JFM THROUGH AMJ ... WHILE BELOW NORMAL TEMPERATURES ARE EXPECTED FOR PORTIONS OF THE NORTH-CENTRAL STATES FOR OND AND NDJ ... MOVING INTO PARTS OF THE NORTHEAST FOR DJF AND JFM. THE TEMPERATURE OUTLOOK FOR NEXT SUMMER AND FALL IS BASED ON OCN. NOTE: THE CHANGE IN NORMALS IMPLEMENTED IN MAY 2001 HAS NOT RESULTED IN ANY MAJOR CHANGES IN THE OUTLOOK PATTERNS... ALTHOUGH SLIGHT WEAKENING IS SHOWN IN SOME OF THE TRENDS FOR WARMTH... AS MIGHT BE EXPECTED. . . . . . . . . PRECIPITATION: ABOVE MEDIAN PRECIPITATION OVER PORTIONS OF THE PLAINS AND SOUTH-CENTRAL STATES IN OND IS INDICATED BY OCN AND SUPPORTED BY THE CMP. THE PRECIPITATION OUTLOOK FOR NDJ 2001 THROUGH JFM 2002 INCLUDES A REGION OF ABOVE MEDIAN PRECIPITATION IN THE SOUTH-CENTRAL TO SOUTHEAST U.S. WHICH COMES FROM OCN AND CMP. CCA INDICATES BELOW MEDIAN PRECIPITATION IN THE DESERT SOUTHWEST FOR NDJ AND DJF 2001. OCN INDICATES ABOVE MEDIAN PRECIPITATION IN THE PACIFIC NORTHWEST FOR AMJ AND MJJ 2002. ABOVE MEDIAN PRECIPITATION OVER A PORTION OF THE PLAINS AND LOWER MISSOURI VALLEY IN MJJ 2002 IS BASED ON OCN AS IS THE BELOW MEDIAN PRECIPITATION OVER THE GREAT BASIN AND SIERRA NEVADAS FOR JAS AND ASO 2002. SMALL AREAS OF ABOVE MEDIAN PRECIPITATION DURING SON AND OND 2002 ARE ALSO FROM OCN. FOR A DESCRIPTION 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/MULTI-SEASON/ 13_SEASONAL_OUTLOOKS/TOOLS (USE LOWER CASE LETTERS) INFORMATION ON THE FORMULATION AND SKILL OF THE CAS FORECASTS MAY BE FOUND AT: HTTP://WWW.CPC.NCEP.NOAA.GOV/SOILMST/FORECASTS.HTML (USE LOWER CASE LETTERS) NOTES - THESE CLIMATE OUTLOOKS ARE INTENDED FOR USE PRIOR TO THE START OF THEIR VALID PERIODS. 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 THURSDAY OCTOBER 18 2001. 1971-2000 BASE PERIOD MEANS WERE IMPLEMENTED EFFECTIVE WITH THE MAY 17 2001 FORECAST RELEASE. NNNN NNNN