PROGNOSTIC DISCUSSION FOR LONG-LEAD OUTLOOKS CLIMATE PREDICTION CENTER NCEP NATIONAL WEATHER SERVICE WASHINGTON DC 3 PM EDT THURSDAY APR 12 2001 BASIS AND SUMMARY OF THE CURRENT LONG-LEAD OUTLOOK . . . . . . . . THE MJJ 2001 FORECASTS REFLECT ONLY TO MINIMAL DEGREE THE U.S. CLIMATE ANOMALIES EXPECTED IN A WEAKENING ENSO COLD EVENT. THE IMPACT OF LA NINA ON US CLIMATE IS WEAK AT THIS TIME OF YEAR. OTHER PERTINENT INFORMATION USED WAS LONG TERM TREND ANDTHE IMPACT OF SOIL MOISTURE ANOMALIES WHICH HOWEVER ARE NOT VERY STRONG THIS YEAR. STATISTICAL PREDICTIONS OF NINO 3.4 INDICATE THE POSSIBILITY OF VERY WEAK WARM ENSO CONDITIONS BY WINTER 2001/2002 BUT EVEN LESS SO THAN A MONTH AGO. GIVEN THE UNCERTAINTIES IN THE OUTLOOK - NEXT WINTERS US FORECASTS DO NOT REFLECT EITHER WARM OR COLD EVENT US IMPACTS. CURRENT ATMOSPHERIC AND OCEANIC CONDITIONS ATMOSPHERIC AND OCEANIC INDICES OF ENSO SHOW DECLINING WEAK COLD PHASE (LA NINA) CONDITIONS. PACIFIC SSTS NEAR THE EQUATOR HAVE DECLINED SINCE LAST MONTH AND ARE AROUND 0.5 DEGREE C BELOW NORMAL FROM 165E TO 155W. THE TRADE WINDS ARE STRONGER THAN NORMAL WEST OF 150W IN THE TROPICAL PACIFIC BUT IN THE EAST PACIFIC THE TRADE WINDS HAVE BEEN WEAK AND SSTS AND NINO3 ARE POSITIVE WITH ENHANCED CONVECTION ALONG THE SA COAST - HOWEVER POSITIVE OCEAN TEMPERATURE ANOMALIES IN THAT AREA ARE SHALLOW. 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 MJJ 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 IS IN BETWEEN THE CCA AND CA. A CONSOLIDATION OF THE THREE MODELS BASED ON THEIR PAST PERFORMANCE PREDICTS THAT NINO 3.4 SST ANOMALIES WILL AVERAGE NEAR ZERO IN MJJ AND THEN INCREASE BEFORE GENERALLY LEVELING OFF AT AROUND 0.5 DEGREES C AT MOST DURING THE SECOND HALF OF 2001. FOR THE MOMENT NEAR-NEUTRAL SST CONDITIONS ARE MOST LIKELY IN THE TROPICAL PACIFIC DURING WINTER 2001-2002. SINCE WE CLEARED THE SPRING BARRIER THE A-PRIORI SKILL FOR NEXT WINTER IS ALREADY QUITE HIGH - A 0.7 CORRELATION. 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 AND CONFIDENCE IN CAS IS RATHER LOW BECAUSE THE US SOIL MOISTURE ANOMALIES ARE WEAK THIS YEAR. AT LONGER LEADS THREE TOOLS WERE USED MAINLY - THE OCN AND CCA AND A HIGH FREQUENCY ENSO COMPOSITE FOR NEUTRAL CASES. THE TIME FILTER IS A NINE YEAR RUNNING MEAN SO AS TO ALLOW EASY ADDITION OF OCN AND ENSO COMPOSITES. . . . . . . . . PROGNOSTIC DISCUSSION OF OUTLOOKS - MJJ 2001 TO MJJ 2002. TEMPERATURE: THE OUTLOOK FOR MMJ 2001 CALLS FOR WARMER THAN NORMAL TEMPERATURES FROM ARIZONA INTO THE DEEP SE - BASED ON CMP-CCA-OCN. CCA AND OCN PREDICT ABNORMAL WARMTH IN CENTRAL AND NORTHERN ALASKA. WE REMOVED THE FORECASTS FOR BELOW NORMAL - SUPPORTED BY SEVERAL TOOLS - IN SOUTHERN ALASKA BECAUSE OF LOW SEA ICE. THIS PIECE OF LOCAL INFORMATION IS MISSING IN OUR TOOLS. . . . . . . . . OCN INDICATES STRONG WARMING TRENDS IN ALASKA IN THE LATE SPRING AND SUMMER. THIS IS SUPPORTED BY THE CCA PREDICTION FOR THE INTERIOR AREAS THRU JAS 2001. 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 MIDWEST IN JJA AND JAS WHEN OCN SLIGHTLY FAVORS 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 FROM THE NORTHWEST THROUGH THE CENTRAL AND SOUTHERN ROCKIES. THE AREA OF ABNORMAL WARMTH SHRINKS RAPIDLY FOLLOWING SON - INCLUDING ONLY SOUTHERN SECTIONS OF CALIFORNIA AND NEVADA ALONG WITH ARIZONA AND SOUTHWESTERN NEW MEXICO. BY OND AND NDJ THE SOUTHWESTERN REGION OF ABOVE NORMAL TEMPERATURES RECEDES FURTHER INTO THE INTERIOR SOUTHWEST AND EXPANDS INTO SOUTHWESTERN TEXAS. THESE FORECASTS REFLECT MAINLY THE INFLUENCE OF CCA AND OCN. 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 ALONE WOULD FAVOR WARMTH - THUS THE TREND MAY BE CONTRADICTED IN ENSO NEUTRAL YEARS ESPECIALLY IN THE NORTHEAST DURING NDJ, DJF AND JFM. THIS EXPLAINS THE LACK OF WARMTH IN THIS NEW SET OF FORECASTS IN 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 FORWARD. NOTE: THE TREND BASED FORECASTS FOR THESE OUTLOOKS IS MOST LIKELY TO CHANGE IN APPEARANCE WHEN NEW NORMALS WILL BE USED. . . . . . . . . PRECIPITATION: PRECIPITATION TRENDS FAVOR RELATIVELY WET EARLY SUMMER CONDITIONS IN THE PACIFIC NORTHWEST - AND THIS IS SUPPORTED BY CMP AND CCA. EVEN IF ABOVE MEDIAN PRECIPITATION FALLS IN THOSE REGIONS - AND OUR FORECAST PROBABILITIES ARE QUITE LOW - IT IS HIGHLY UNLIKELY TO BE SUFFICIENT TO SIGNIFICANTLY IMPROVE WATER CONDITIONS THERE - PATICULARLY SINCE NORMALS ARE VERY LOW. THE MJJ PRECIPITATION OUTLOOKS FOR ABNORMALLY DRY CONDITIONS OVER THE SOUTHEAST REFLECT THE CMP FORECAST - AS WELL AS INDICATIONS FROM BOTH CCA AND SMLR. THE CAS STRONGLY FAVORS ABNORMAL DRYNESS IN THE SOUTHEAST. . . . . . . . . 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 IN NORTH TX AND OK. 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 HAVE WITHDRAWN ANY INDICATION FOR A WET MONSOON BASED ON LA NINA. THIS IS PARTLY BECAUSE ENSO IS UNCLEAR AT THE MOMENT AND BECAUSE NO FORMAL TOOL SUPPORTS SUCH A FORECAST. AN ADDITIONAL FACTOR IS THAT MJO ACTIVITY MODULATES THE SOUTHWEST MONSOON - THIS OCCURRED IN 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 MAY 17 2001. 1971-2000 BASE PERIOD MEANS WILL BE IMPLEMENTED BEGINNING WITH THE FORECAST ISSUED MAY 17, 2001. NNNN NNNN