PROGNOSTIC DISCUSSION FOR LONG-LEAD OUTLOOKS CLIMATE PREDICTION CENTER NCEP NATIONAL WEATHER SERVICE WASHINGTON DC 3 PM EDT THURSDAY MAY 17 2001 BASIS AND SUMMARY OF THE CURRENT LONG-LEAD OUTLOOK . . . . . . . . THE JJA 2001 FORECASTS REFLECT SOIL MOISTURE CONDITIONS WHICH STRENGHTENED DURING APRIL AND THE LONG-TERM TREND AS ESTIMATED BY OCN. TROPICAL PACIFIC OCEAN TEMPERATURES ARE NOT EXPECTED TO HAVE ANY IMPACT ON JJA 2001 SINCE WATER TEMPERATURES HAVE RETURNED TO NEAR NORMAL AND ARE EXPECTED TO REMAIN NEAR NORMAL THROUGHOUT THE SEASON. SOME STATISTICAL AND DYNAMICAL PREDICTIONS OF NINO 3.4 INDICATE THE POSSIBILITY OF VERY WEAK WARM EPISODE (EL NINO) CONDITIONS BY WINTER 2001/2002. HOWEVER OTHER FORECASTS INDICATE EITHER SOMEWHAT COOLER THAN NORMAL OR NEAR NORMAL CONDITIONS IN THE TROPICAL PACIFIC. GIVEN THE UNCERTAINTIES IN THE SST OUTLOOK - NEXT WINTERS US FORECASTS DO NOT REFLECT EITHER WARM OR COLD EPISODE US IMPACTS. CURRENT ATMOSPHERIC AND OCEANIC CONDITIONS ATMOSPHERIC AND OCEANIC INDICES OF ENSO SHOW EITHER NEAR NORMAL OR WEAK LA NINA CONDITIONS. PACIFIC SST ANOMALIES ARE NEAR ZERO THROUGHOUT THE EQUATORIAL PACIFIC. HOWEVER THE TRADE WINDS REMAIN STRONGER THAN NORMAL WEST OF 150W IN THE TROPICAL PACIFIC. THE TRADE WINDS HAVE INCREASED IN INTENSITY THROUGHOUT THE EASTERN TROPICAL PACIFIC RESULTING IN A COOLING OF OCEAN SURFACE TEMPERATURES ALONG THE WEST COAST OF SOUTH AMERICA AND ALONG THE EQUATOR IN THE EASTERN PACIFIC. BELOW THE SURFACE THERE HAS BEEN A SLOW EASTWARD SHIFT OF THE POSITIVE TEMPERATURE ANOMALIES IN THE WEST PACIFIC SINCE LATE 1998. RECENTLY THERE HAS BEEN A SERIES OF EASTWARD AND WESTWARD SHIFTS OF THE EASTERN EDGE OF THIS WARM POOL. THESE SHIFTS APPEAR TO BE RELATED TO THE 30-60 DAY (MJO) OSCILLATION. A PERSISTENT EASTWARD SHIFT COULD CONTRIBUTE TO SURFACE WARMING FARTHER EAST AT A LATER TIME. . . . . . . . . PROGNOSTIC DISCUSSION OF SST FORECASTS THE NCEP DYNAMIC AND STATISTICAL MODELS (THE CONSTRUCTED ANALOG (CA) METHOD AND CANONICAL CORRELATION ANALYSIS (CCA)) PREDICT ESSENTIALLY NEAR NORMAL NINO 3.4 REGION (5N TO 5S AND 120-170W) SSTS FROM JJA 2001 FORWARD. THE CA SST FORECAST HOLDS TEMPERATURES CLOSEST TO ZERO THROUGH THE END OF THE YEAR. THE CCA IS AT LEAST 0.5 DEGREE WARMER THAN CA THROUGH MOST OF THE YEAR. THE COUPLED MODEL SST OUTLOOK INDICATES POSITIVE SST ANOMALIES BETWEEN 0.5 AND 1 DEGREE C BY THE END OF THE YEAR. A CONSOLIDATION OF THE THREE MODELS BASED ON THEIR PAST PERFORMANCE PREDICTS THAT NINO 3.4 SST ANOMALIES WILL AVERAGE NEAR ZERO IN JJA AND THEN INCREASE SLOWLY BEFORE GENERALLY LEVELING OFF AT AROUND 0.5 DEGREES C AT MOST DURING THE SECOND HALF OF 2001. SINCE SST ANOMALIES OF THAT MAGNITUDE DO NOT HAVE ANY APPRECIABLE IMPACT ON TROPICAL RAINFALL UNTIL LATE WINTER - EARLY SPRING WE DO NOT EXPECT ANY ENSO-RELATED IMPACTS DURING FALL 2001 AND EARLY WINTER 2001-2002. SINCE THERE IS A LACK OF CONSISTENCY IN THE VARIOUS SST FORECASTS AT THE LONGER LEADS WE CHOSE ENSO-NEUTRAL AS THE MOST LIKELY STATE FOR THIS SERIES OF FORECASTS. PROGNOSTIC TOOLS USED FOR U.S. TEMPERATURE AND PRECIPITATION OUTLOOK THE CCA - OCN AND SMLR WERE CONSULTED AT ALL LEAD TIMES. THE CONSTRUCTED ANALOG SOIL MOISTURE-BASED FORECAST TOOL (CAS) WHICH INCORPORATES THE HISTORICAL INFLUENCE OF SOIL MOISTURE ANOMALIES INTO FORECASTS OF TEMPERATURE AND PRECIPITATION WAS USED FOR THE WARM SEASON FORECASTS. ALL TOOLS PLUS THE CMP INFLUENCED THE FORECAST FOR THE FIRST THREE LEAD TIMES. THE COUPLED MODEL HAD ONLY WEAK SIGNALS. THE STRENGTHENED SOIL MOISTURE ANOMALY PATTERN OVER THE COUNTRY CONTRIBUTED TO OUR USING THIS TOOL MORE THAN LAST MONTH. AT LONGER LEADS TWO TOOLS WERE USED - THE OCN AND CCA. . . . . . . . . PROGNOSTIC DISCUSSION OF OUTLOOKS - JJA 2001 TO JJA 2002. TEMPERATURE: THE OUTLOOK FOR JJA 2001 CALLS FOR WARMER THAN NORMAL TEMPERATURES FROM ARIZONA INTO THE DEEP SOUTHEAST - BASED ON CAS AND CCA-OCN. WARM SEASON PROBABILITIES FOR ABOVE NORMAL TEMPERATURES ARE HIGHEST IN THE SOUTH AND SOUTHWEST WHERE YEAR-TO-YEAR VARIABILITY IS SMALL IN RELATION TO THE TRENDS. CLIMATOLOGICAL ODDS ARE FAVORED OVER MOST OF THE NORTHERN AND CENTRAL PARTS OF THE COUNTRY EXCEPT FOR PORTIONS OF THE CENTRAL PLAINS IN JJA AND JAS WHEN OCN AND CAS FAVOR BELOW NORMAL. CAS INDICATES ABNORMALLY COLD TEMPERATURES IN THE CENTRAL AND NORTH-CENTRAL US IN JJA AND JAS AS WELL. COVERAGE OF THE WEST BY WARMTH PEAKS IN JAS AND ASO WHEN ABOVE NORMAL IS PREDICTED TO EXPAND NORTHWARD TO INCLUDE THE NORTHWEST AND THE CENTRAL ROCKIES. THE AREA OF ABNORMAL WARMTH SHRINKS THEREAFTER WITH ONLY SOUTHERN SECTIONS OF CALIFORNIA AND NEVADA ALONG WITH ARIZONA AND SOUTHWESTERN NEW MEXICO INDICATED TO BE ABOVE NORMAL BY SON. BY OND THE SOUTHWESTERN US IS EXPECTED TO BE NEAR NORMAL WITH ONLY SOUTHERN FLORIDA PREDICTED TO BE ABOVE NORMAL. OCN INDICATES A RETURN OF THE ABNORMAL WARMTH IN THE SOUTHWEST DURING NDJ. AT THE SAME TIME WARMER THAN NORMAL TEMPERATURES ARE PREDICTED FOR SOUTHERN ALASKA. ENSO-NEUTRAL CONDITIONS ARE ASSUMED FOR OND-MJJ 2001-2002 TEMPERATURE OUTLOOKS. WE THUS INVOKED HIGH FREQUENCY NEUTRAL ENSO COMPOSITES THAT SHOW COLD IN SEVERAL AREAS WHERE OCN AND CCA FAVOR WARMTH. THUS THE TREND MAY BE CONTRADICTED IN ENSO NEUTRAL YEARS ESPECIALLY IN THE NORTHEAST AND MIDWEST DURING NDJ, DJF AND JFM. THIS EXPLAINS THE LACK OF WARMTH IN THIS SET OF FORECASTS FOR MUCH OF THE EAST IN WINTER 2001/2002. WITH THE EXCEPTION OF OND WE PREDICT WARMER THAN NORMAL IN ALL SEASONS IN THE SOUTHWEST. WIDESPREAD WARMTH IS ALSO FORECAST FOR THE WEST AND IN ALASKA FOR JFM 2002 FORWARD. NOTE: THE CHANGE IN NORMALS HAS NOT RESULTED IN ANY MAJOR CHANGES IN THE OUTLOOK PATTERNS. . . . . . . . . PRECIPITATION: THE JJA PRECIPITATION OUTLOOK IS FOR CLIMATOLOGICAL PROBABLILITIES FOR AREAS THAT HAVE BEEN SUFFERING LONG-TERM MOISTURE DEFICITS - THE SOUTHEAST AND THE NORTHWEST. THUS NO SUBSTANTIAL RELIEF IS EXPECTED IN THOSE AREAS DURING THE SUMMER SEASON. ALONG WITH BELOW NORMAL TEMPERATURE CAS INDICATES ABOVE NORMAL PRECIP IN THE HEARTLAND IN JJA AND JAS. IN THIS AREA CAS IS ACTING ON INITIALLY WET SOIL - RECYCLING MOISTURE AND DUMPING IT SOMEWHAT DOWNSTREAM FROM THE INITIAL WETNESS. OCN INDICATES BELOW MEDIAN PRECIPITATION IN JAS IN THE FAR WEST AND NORTHWEST. INDICATIONS FOR ASO AND SON WERE WEAK EVERYWHERE AND CL WAS PREDICTED. WE SEE NO INDICATIONS THAT THE SOUTHWEST US MONSOON WILL BE EITHER STRONGER OR WEAKER THAN NORMAL. THIS IS PARTLY BECAUSE THE TROPICAL PACIFIC WATER TEMPERATURES ARE NEAR NORMAL AND THEY ARE EXPECTED TO REMAIN NEAR NORMAL THROUGH THE SUMMER SEASON. AN ADDITIONAL FACTOR THAT CONTRIBUTES TO UNCERTAINTY IS THE TROPICAL MJO ACTIVITY WHICH STRONGLY MODULATED THE SOUTHWEST MONSOON DURING THE SUMMER 2000. THE PRECIPITATION OUTLOOK FOR OND THROUGH DJF INCLUDES A REGION OF ABNORMAL WETNESS IN THE CENTRAL AND SOUTH-CENTRAL US WHICH COMES FROM OCN. LIKEWISE THE CHANCE RISES FOR ABOVE MEDIAN PRECIPITATION OVER PORTIONS OF THE SOUTHERN U.S. - HOWEVER THE PROBABILITY SHIFT IS VERY SMALL - INDICATING A HIGH DEGREE OF UNCERTAINTY. OCN DOES INDICATE ABOVE MEDIAN PRECIPITATION FOR PORTIONS OF THE PLAINS AND TEXAS FOR OND 2001 THROUGH JFM 2002. PRECIPITATION FORECASTS FOR FMA-MJJ ARE MAINLY CL EVERYWHERE - EXCEPT FOR A FORECAST OF ABOVE IN AMJ AND MJJ 2002 IN THE NORTHWEST BASED ON 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 JUNE 14 2001. 1971-2000 BASE PERIOD MEANS HAVE BEEN IMPLEMENTED EFFECTIVE WITH TODAYS FORECAST RELEASE. NNNN NNNN