PROGNOSTIC DISCUSSION FOR LONG-LEAD OUTLOOKS CLIMATE PREDICTION CENTER NCEP NATIONAL WEATHER SERVICE WASHINGTON DC 3 PM EDT THURSDAY JULY 12 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. AT EARLY LEADS THE OUTLOOKS ALSO REFLECT SOIL MOISTURE CONDITIONS ...WHICH HAVE CHANGED CONSIDERABLY IN THE GULF COAST STATES DURING THE LAST TWO MONTHS. TROPICAL PACIFIC OCEAN TEMPERATURES ARE NOW NEAR NORMAL. SOME STATISTICAL AND DYNAMICAL PREDICTIONS OF NINO 3.4 SSTS INDICATE THE POSSIBILITY OF WEAK WARM EPISODE (EL NINO) CONDITIONS BY THE END OF THE YEAR. HOWEVER OTHER FORECASTS INDICATE EITHER NEAR NORMAL OR EVEN SOMEWHAT COOLER-THAN-NORMAL CONDITIONS IN THE TROPICAL PACIFIC. GIVEN THE UNCERTAINTIES IN THE SST OUTLOOK - NEXT WINTERS U.S. FORECASTS PRIMARILY REFLECT THE EXPECTED U.S. CLIMATE ANOMALIES FOR ENSO-NEUTRAL CONDITIONS AND A NEAR-NEUTRAL SEASONAL PHASE OF THE NORTH ATLANTIC OSCILLATION. THE LONGER LEAD OUTLOOKS FOR SPRING AND SUMMER 2002 ALSO DO NOT REFLECT ANY DIRECT INFLUENCES OF ENSO SINCE THE CLIMATE SIGNALS ARE WEAK DURING THOSE SEASONS. CURRENT ATMOSPHERIC AND OCEANIC CONDITIONS NEAR-NORMAL ATMOSPHERIC AND OCEANIC CONDITIONS PREVAILED IN THE TROPICAL PACIFIC DURING JUNE. SST ANOMALIES AVERAGED LESS THAN 1 DEG C AT ALL LOCATIONS IN THE TROPICAL PACIFIC EXCEPT ALONG THE IMMEDIATE SOUTH AMERICAN COAST WHERE NEGATIVE ANOMALIES OF AROUND -1 DEG C WERE FOUND. THE OCEANIC THERMOCLINE REMAINED DEEPER-THAN-NORMAL IN THE EQUATORIAL WEST-CENTRAL AND WESTERN PACIFIC WITH TEMPERATURES AVERAGING UP TO 4 DEG C ABOVE NORMAL AT THERMOCLINE DEPTH. THE NEGATIVE TEMPERATURE ANOMALIES THAT HAVE CHARACTERIZED THE SUBSURFACE THERMAL STRUCTURE IN THE EASTERN PACIFIC SINCE LATE 1998 HAVE CONTINUED TO WEAKEN. THE PATTERN OF ANOMALOUS TROPICAL CONVECTION WAS RATHER DISORGANIZED DURING JUNE... WITH AREAS OF ABOVE NORMAL PRECIPITATION OVER INDONESIA AND ALONG THE SOUTH PACIFIC CONVERGENCE ZONE (SPCZ) AND BELOW-NORMAL PRECIPITATION NEAR THE DATE LINE. CONSISTENT WITH THIS ... THE LOW-LEVEL WINDS ACROSS THE CENTRAL AND WESTERN TROPICAL PACIFIC WERE WEAK. . . . . . . . . PROGNOSTIC DISCUSSION OF SST FORECASTS OVER THE PAST TWO YEARS THERE HAS BEEN A GRADUAL EASTWARD EXPANSION OF THE AREA OF POSITIVE SUBSURFACE TEMPERATURE ANOMALIES INTO THE CENTRAL PACIFIC. SEA SURFACE TEMPERATURES NEAR THE INTERNATIONAL DATELINE HAVE GRADUALLY WARMED AND ARE NOW SLIGHTLY WARMER-THAN-NORMAL FOR THE FIRST TIME SINCE THE 1997-98 El NINO. THIS EVOLUTION IS CONSISTENT WITH A DECAY OF THE SUBSURFACE THERMAL STRUCTURE THAT CHARACTERIZES THE MATURE PHASE OF COLD EPISODES...TOWARDS A PRE-WARM EPISODE STATE. THUS IT IS LIKELY THAT NEAR-NORMAL OR SLIGHTLY WARMER-THAN-NORMAL CONDITIONS WILL PERSIST FOR THE REMAINDER OF 2001. THIS ASSESSMENT IS GENERALLY SUPPORTED BY THE MOST RECENT NCEP STATISTICAL (CONSTRUCTED ANALOG METHOD (CA) AND CANONICAL CORRELATION ANALYSIS (CCA)) AND COUPLED MODEL FORECASTS WHICH INDICATE NEAR-NORMAL OR SLIGHTLY WARMER-THAN- NORMAL CONDITIONS INTO EARLY 2002. THE AUTOMATED OFFICIAL FORECAST...WHICH IS A CONSOLIDATION OF THE 3 MODELS BASED ON PAST PERFORMANCE...INDICATES NEAR- NORMAL TO SLIGHTLY WARMER-THAN-NORMAL CONDITIONS THROUGH NEXT SPRING. THE FORECAST BEYOND NEXT SPRING BECOMES HIGHLY UNCERTAIN. IT IS WORTH EMPHASIZING THAT THE RECENT WARMING IN THE TROPICAL PACIFIC HAS BEEN PRIMARILY NEAR THE INTERNATIONAL DATE LINE. THE IMPACTS OF A CENTRAL PACIFIC WARMING ON U.S. PRECIPITATION AND TEMPERATURE PATTERNS THIS WINTER ARE LIKELY TO BE WEAK. HENCE THESE OUTLOOKS PRIMARILY REFLECT THE EXPECTED U.S. CLIMATE ANOMALIES FOR ENSO-NEUTRAL CONDITIONS. PROGNOSTIC TOOLS USED FOR U.S. TEMPERATURE AND PRECIPITATION OUTLOOK THE CCA - OCN AND SOIL MOISTURE TOOLS 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 FOUR LEAD TIMES. THE COUPLED MODEL HAD MOSTLY WEAK SIGNALS... AND PRODUCED SOMEWHAT DIFFERENT FORECASTS DEPENDING UPON WHETHER IT INCORPORATED SOIL MOISTURE. THE 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 OCN WAS GIVEN THE MOST WEIGHT...WITH SOME USE OF COMPOSITES. COMPOSITES OF PRECIPITATION AND TEMPERATURE ANOMALIES FOR ENSO-NEUTRAL AND AO-NEUTRAL YEARS IN THE 1990S MAY BE INTERPRETED AS AN OCN FOR NEUTRAL CONDITIONS. THE COOL TEMPERATURES INDICATED BY ESTIMATES OF THE TREND FOR ENSO-NEUTRAL CONDITIONS AND BY THE CMP FORECASTS WERE USED TO TEMPER COLD SEASON PROBABILITIES FOR ABOVE NORMAL TEMPERATURES IN THE NORTHERN HALF OF THE COUNTRY. . . . . . . . . PROGNOSTIC DISCUSSION OF OUTLOOKS - ASO 2001 TO ASO 2002. TEMPERATURE: THE OUTLOOK FOR ASO 2001 CALLS FOR ABOVE NORMAL TEMPERATURES OVER THE SOUTHWEST AND WEST AS WELL AS THE FLORIDA PENINSULA - BASED ON CAS AND CCA-OCN. THE WARMTH THAT WAS INDICATED ACROSS THE GULF STATES IN THE PREVIOUS FORECAST HAS BEEN TEMPERED 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 EASTERN HALF OF THE NATION. WARMTH IN THE WEST PEAKS IN ASO AND DECREASES THEREAFTER WITH ONLY SOUTHERN SECTIONS OF CALIFORNIA AND NEVADA ALONG WITH ARIZONA AND SOUTHWESTERN NEW MEXICO INDICATED TO BE ABOVE NORMAL FROM SON THROUGH NDJ. OCN INDICATES AN INCREASE IN COVERAGE OF THE ABNORMAL WARMTH IN THE SOUTHWEST DURING NDJ... EVENTUALLY EXPANDING NORTHWARD AGAIN FROM DJF THROUGH MAM. ABOVE NORMAL TEMPERATURES ARE ALSO PREDICTED FOR SOUTHERN ALASKA BEGINNING IN DJF AND EXPANDING OVER MUCH OF THE STATE THROUGH SUMMER 2002. THE FORECASTS FOR OND 2001 THROUGH DJF 2001-2002 ALSO REFLECT THE LONG TERM TRENDS TEMPERED BY ESTIMATES OF THE TREND FOR ENSO-NEUTRAL CONDITIONS... THAT SHOW COLD IN THE NORTHERN PLAINS AND UPPER MIDWEST WHERE OCN AND CCA FAVOR WARMTH. THE TREND IS CONTRADICTED IN ENSO NEUTRAL YEARS IN THESE REGIONS DURING OND, NDJ AND DJF... AS IT WAS FOR MUCH OF THE TIME LAST WINTER DUE TO LENGTHY PERIODS WITH NEGATIVE AO/NAO. CURRENTLY THERE IS NO CAPABILITY TO FORECAST THE SEASONAL PHASE OF THE AO/NAO ...WHICH INTRODUCES SOME ADDITIONAL UNCERTAINTY IN THE FORECASTS ALONG THE EASTERN SEABOARD. 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. THE NCEP CMP ALSO LENDS SUPPORT FOR THIS SOLUTION. WITH THE EXCEPTION OF OND WE EXPECT WIDESPREAD WARMTH 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 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: THE ASO PRECIPITATION OUTLOOK INDICATES ABOVE MEDIAN PRECIPITATION OVER PORTIONS OF THE SOUTHEAST...WHERE CAS IS ACTING ON INITIALLY WET SOIL - RECYCLING MOISTURE - AND DUMPING IT SOMEWHAT DOWNSTREAM . OCN INDICATES BELOW MEDIAN PRECIPITATION FOR ASO OVER THE FAR WEST... WITH SOME SUPPORT FROM CAS. WE SEE NO INDICATIONS THAT THE SOUTHWEST U.S. MONSOON WILL BE EITHER STRONGER OR WEAKER THAN NORMAL. THIS IS PARTLY DUE TO ENSO-NEUTRAL CONDITIONS IN THE TROPICAL PACIFIC ...WHICH ARE EXPECTED TO PERSIST DURING THE REMAINDER OF THE WARM SEASON. AN ADDITIONAL FACTOR THAT CONTRIBUTES TO UNCERTAINTY IS THE TROPICAL MJO ACTIVITY WHICH CAN BE A CONTROLLING FACTOR ON MONSOON RAINFALL ON INTRASEASONAL 30-60 DAY TIMESCALES. THE ANOMALOUS PATTERN OF TROPICAL CONVECTION HAS BEEN RATHER DISORGANIZED OVER THE LAST MONTH OR TWO INDICATING THAT MJO ACTIVITY IS RATHER WEAK. 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. IN ADDITION PRECIPITATION COMPOSITES BASED ON OCN FOR ENSO-NEUTRAL CONDITIONS INDICATE ABOVE MEDIAN PRECIPITATION EXTENDING FROM THE WESTERN GULF COAST STATES TO THE CENTRAL APPALACHIANS DURING DJF AND JFM. THERE ARE HINTS FOR DRYNESS OVER THE NORTHWEST FOR SEVERAL OF THE COLD SEASONS BUT THE LIKELY SKILL AND AREAL COVERAGE ARE NOT SIGNIFICANT. PRECIPITATION FORECASTS FOR MAM THROUGH ASO 2002 ARE CL AT MOST LOCATIONS - EXCEPT FOR A FORECAST OF ABOVE MEDIAN PRECIPITATION OVER THE PACIFIC NORTHWEST IN AMJ AND MJJ 2002 BASED ON OCN-ABOVE MEDIAN PRECIPITATION OVER THE NORTHERN PLAINS DURING MJJ, JJA AND JAS 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 AUGUST 16 2001. 1971-2000 BASE PERIOD MEANS WERE IMPLEMENTED EFFECTIVE WITH THE MAY 17 2001 FORECAST RELEASE. NNNN NNNN