PROGNOSTIC DISCUSSION FOR LONG-LEAD OUTLOOKS CLIMATE PREDICTION CENTER NCEP NATIONAL WEATHER SERVICE WASHINGTON DC 3 PM EDT THURSDAY JUNE 14 2001 BASIS AND SUMMARY OF THE CURRENT LONG-LEAD OUTLOOK . . . . . . . . THE JAS 2001 FORECASTS PRIMARILY REFLECT SOIL MOISTURE CONDITIONS... WHICH HAVE CHANGED CONSIDERABLY IN THE GULF STATES DUE TO RECENT HEAVY RAINS... AND THE LONG-TERM TREND AS ESTIMATED BY OCN. TROPICAL PACIFIC OCEAN TEMPERATURES ARE NOT EXPECTED TO HAVE ANY IMPACT ON JAS 2001 SINCE WATER TEMPERATURES ARE NOW NEAR NORMAL AND ARE EXPECTED TO REMAIN THAT WAY THROUGHOUT THE UPCOMING SEASONS. SOME STATISTICAL AND DYNAMICAL PREDICTIONS OF NINO 3.4 SSTS 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 U.S. FORECASTS DO NOT REFLECT EITHER WARM OR COLD EPISODE U.S. IMPACTS. CLIMATOLOGICALLY... A WARM EVENT WOULD BE MORE LIKELY TO BEGIN IN THE SPRING OR 2002... BUT EVEN THAT IS SO UNCERTAIN AT THIS TIME THAT THE LONGER LEAD OUTLOOKS FOR SPRING AND SUMMER 2002 ALSO DO NOT REFLECT ANY DIRECT INFLUENCES OF ENSO. THE CLIMATE SIGNALS WOULD BE WEAK DURING THOSE SEASONS ANYWAY EVEN IF A WARM EVENT DOES BEGIN IN SPRING 2002. CURRENT ATMOSPHERIC AND OCEANIC CONDITIONS ATMOSPHERIC AND OCEANIC INDICES SHOW EITHER NEAR NORMAL OR VERY WEAK RESIDUAL LA NINA CONDITIONS. PACIFIC SST ANOMALIES ARE WITHIN A HALF DEGREE C OF NORMAL THROUGHOUT THE EQUATORIAL PACIFIC. HOWEVER THE TRADE WINDS REMAIN STRONGER THAN NORMAL WEST OF 150W IN THE TROPICAL PACIFIC... AND 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... CONFIRMING THAT A WARM EVENT IS NOT BEGINNING AT THIS TIME. RECENT OUTGOING LONG WAVE RADIATION MEASUREMENTS SHOW ACTIVE CONVECTION IN THE ASIAN MONSOON AREAS AND OFF THE WEST COAST OF CENTRAL AMERICA BUT NO SIGN OF CONVECTION NEAR THE EQUATOR OVER THE EASTERN OR CENTRAL PACIFIC. BELOW THE OCEAN SURFACE THERE HAS BEEN A VERY SLOW EASTWARD SHIFT OF POSITIVE TEMPERATURE ANOMALIES IN THE WEST PACIFIC SINCE LATE 1998. RECENTLY THERE HAS BEEN A SERIES OF EASTWARD ADVANCES AND WESTWARD RETREATS OF THE EASTERN EDGE OF THIS SUBSURFACE WARMTH... BUT WITH A SLOW NET EASTWARD PROGRESS. 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 THE DEVELOPMENT OF WEAK WARMING IN THE NINO 3.4 REGION (5N TO 5S AND 120-170W) SSTS FROM JAS 2001 FORWARD. THE CA SST FORECAST HOLDS TEMPERATURES NEAR OR SLIGHTLY BELOW NORMAL THROUGH THE FIRST HALF OF 2002. THE CCA IS BETWEEN 0.5 AND 1.0 DEGREE WARMER THAN CA THROUGH MOST OF THE PERIOD. THE COUPLED MODEL SST OUTLOOK INDICATES POSITIVE SST ANOMALIES OF ABOUT 0.5 C INTO EARLY NEXT YEAR. A CONSOLIDATION OF THE THREE MODELS BASED ON THEIR PAST PERFORMANCE PREDICTS THAT NINO 3.4 SST ANOMALIES WILL AVERAGE NEAR ZERO FROM JAS THROUGH THE END OF THE YEAR AND THEN INCREASE DURING LATE WINTER AND EARLY SPRING 2002 TO AROUND PLUS 0.5 TO 1.0 DEGREES C. THUS WE DO NOT EXPECT ANY ENSO-RELATED IMPACTS DURING THE COMING FALL OR WINTER. SINCE THERE IS A LACK OF CONSISTENCY IN THE VARIOUS SST FORECASTS AT INTERMEDIATE 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 2001 WARM SEASON FORECASTS. ALL TOOLS PLUS THE CMP INFLUENCED THE FORECAST FOR THE FIRST THREE LEAD TIMES. THE COUPLED MODEL HAD MOSTLY WEAK SIGNALS... AND PRODOUCED QUITE DIFFERENT FORECASTS DEPENDING UPON WHETHER IT INCORPORATED SOIL MOISTURE. THE USUAL RELATIVELY GOOD PERFORMANCE OF THE CAS MODEL IN SUMMER CONTRIBUTED TO THIS TOOL BEING WEIGHTED MORE THAN THE OTHERS IN THE FIRST FEW LEADS. AT LONGER LEADS CCA AND OCN WERE GIVEN THE MOST WEIGHT... WITH SOME USE OF COMPOSITE STRATIFIED CLIMATOLOGIES FROM PAST CASES WITH ENSO AND THE AO (ARCTIC OSCILLATION) BOTH NEUTRAL. . . . . . . . . PROGNOSTIC DISCUSSION OF OUTLOOKS - JAS 2001 TO JAS 2002. TEMPERATURE: THE OUTLOOK FOR JAS 2001 CALLS FOR WARMER THAN NORMAL TEMPERATURES OVER THE SOUTHWEST AND WEST AS WELL AS THE FLORIDA PENINSULA - BASED ON CAS AND CCA-OCN. NOTE THAT THE WARMTH THAT WAS INDICATED ACROSS THE GULF STATES IN THE LAST FORECAST HAS BEEN REMOVED DUE TO RECENT HEAVY RAINS AND A RADICAL CHANGE IN THE SOIL MOISTURE THERE. WARM SEASON PROBABILITIES FOR ABOVE NORMAL TEMPERATURES REMAIN HIGHEST IN THE 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 AND NORTHERN PLAINS AND UPPER MISSISSIPPI VALLEY IN JAS WHEN OCN AND CAS BOTH FAVOR BELOW NORMAL AND CURRENTLY STRONG MCS ACTIVITY WILL KEEP THE GROUND MOIST. 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 FROM SON THROUGH DJF... EXCEPT FOR OND WHEN EVEN THE SOUTH- WESTERN US IS EXPECTED TO BE NEAR NORMAL OR CL WITH ONLY SOUTHERN FLORIDA PREDICTED TO BE ABOVE NORMAL. OCN INDICATES A RETURN OF THE ABNORMAL WARMTH IN THE SOUTHWEST DURING NDJ... EVENTUALLY EXPANDING NORTHWARD AGAIN FROM JFM THROUGH MAM. ABOVE NORMAL TEMPERATURES ARE PREDICTED FOR SOUTHERN ALASKA BEGINNING IN NDJ AND EXPANDING OVER MUCH OF THE STATE THROUGH SUMMER 2002. ENSO-NEUTRAL CONDITIONS ARE ASSUMED FOR THE ASO 2001 THROUGH MAM 2002 TEMPERATURE OUTLOOKS... AND AFTER THAT A WEAK WARM EVENT IS CONSIDERED POSSIBLE BUT WITH HIGH UNCERTAINTY AND LITTLE EXPECTED IMPACT ON THE U.S. CLIMATE AT THAT RANGE EVEN IF IT DOES OCCUR. WE THUS INVOKED HIGH FREQUENCY (DETRENDED) 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... AS IT WAS FOR MUCH OF THE TIME LAST WINTER DUE TO LENGTHY PERIODS WITH NEGATIVE AO/NAO. ALTHOUGH THE PHASE OF THE AO/NAO CANNOT BE PREDICTED THIS FAR AHEAD... THE CLIMATOLOGICAL RECORD HINTS THAT THE STRONG POSITIVE PHASES OF THE AO/NAO ASSOCIATED WITH THE PREDOMINANTLY VERY MILD WINTERS OF THE 90S MAY HAVE PEAKED IN THE EARLY PART OF THE LAST DECADE. THIS EXPLAINS THE LACK OF PREDICTED WARMTH IN THIS SET OF FORECASTS FOR MUCH OF THE EAST DURING WINTER 2001/2002 IN AREAS WITH STRONG OCN AND CCA SIGNALS FOR WARMTH. WITH THE EXCEPTION OF OND WE EXPECT 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 IMPEMENTED LAST MONTH 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: THE JAS PRECIPITATION OUTLOOK IS FOR CLIMATOLOGICAL PROBABLILITIES FOR AREAS OF THE SOUTHEAST THAT HAVE BEEN SUFFERING LONG-TERM MOISTURE DEFICITS. THUS NO SUBSTANTIAL LONG-TERM RELIEF IS EXPECTED IN THIS AREA DURING THE SUMMER SEASON ... ALTHOUGH NEAR NORMAL PRECIPITATION DURING THE RAINY SEASON WOULD PROVIDE AN IMPROVEMENT IN TOPSOIL MOISTURE. IN THE NORTH-CENTRAL STATES CAS IS ACTING ON INITIALLY WET SOIL - RECYCLING MOISTURE AND DUMPING IT SOMEWHAT DOWNSTREAM FROM THE INITIAL WETNESS - THUS ABOVE MEDIAN RAINFALL IS PREDICTED THERE. OCN INDICATES BELOW MEDIAN PRECIPITATION FOR JAS AND TO A LESSER EXTENT DURING ASO OVER THE FAR WEST AND NORTHWEST... WITH SOME SUPPORT FROM CAS. INDICATIONS FOR ASO AND SON WERE NOTICEABLY WEAKER SO CL WAS INDICATED OVER MOST OF THE COUNTRY. WE SEE NO INDICATIONS THAT THE SOUTHWEST U.S. MONSOON WILL BE EITHER STRONGER OR WEAKER THAN NORMAL. THIS IS PARTLY BECAUSE THE TROPICAL PACIFIC SEA SURFACE 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 AND IS OFTEN A CONTROLLING BUT ESSENTIALLY UNPREDICTABLE FACTOR AT LONGER RANGES DURING ENSO NEUTRAL CONDITIONS. THE PRECIPITATION OUTLOOK FOR OND 2001 THROUGH FMA 2002 INCLUDES A REGION OF ABNORMAL WETNESS IN THE SOUTH-CENTRAL U.S. WHICH COMES FROM OCN WHICH INDICATES ABOVE MEDIAN PRECIPITATION FOR PORTIONS OF THE PLAINS... TEXAS AND WESTERN LOUISIANA FROM LATE FALL THROUGH EARLY SPRING OF NEXT YEAR. THERE ARE HINTS FOR DRYNESS OVER THE NORTHWEST FOR SEVERAL OF THE COLDER SEASONS BUT THE LIKELY SKILL AND AREA OF COVERAGE ARE SIGNIFICANT ENOUGH TO BE FORECAST ONLY FOR NDJ. PRECIPITATION FORECASTS FOR FMA THROUGH JJA 2002 ARE MAINLY CL EVERYWHERE - EXCEPT FOR A REMNANT OF WETNESS OVER THE CENTRAL GULF REGION DURING FMA - A FORECAST OF ABOVE MEDIAN OVER THE PACIFIC NORTHWEST IN AMJ AND MJJ 2002 BASED ON OCN - AND DRYNESS OVER THE FAR WEST DURING JAS 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 JULY 12 2001. 1971-2000 BASE PERIOD MEANS WERE IMPLEMENTED EFFECTIVE WITH THE MAY 17 2001 FORECAST RELEASE. NNNN NNNN