PROGNOSTIC DISCUSSION FOR LONG-LEAD OUTLOOKS CLIMATE PREDICTION CENTER NCEP NATIONAL WEATHER SERVICE WASHINGTON DC 3 PM EST THURSDAY DECEMBER 13 2001 BASIS AND SUMMARY OF THE CURRENT LONG-LEAD OUTLOOK . . . . . . . . THESE OUTLOOKS REFLECT THE EXPECTED U.S. CLIMATE ANOMALIES FOR ENSO-NEUTRAL CONDITIONS - THE LONG-TERM TREND AS ESTIMATED BY OCN AND FORECASTS OF OCEANIC AND ATMOSPHERIC CONDITIONS FROM DYNAMICAL MODELS. FORECASTS FOR THE WINTER SEASONS A YEAR FROM NOW ARE INFLUENCED BY EL NINO COMPOSITES. PACIFIC SSTS ARE NOW SLIGHTLY ABOVE NORMAL WEST OF THE DATE LINE AND BELOW NORMAL EAST OF 150W. THIS SST PATTERN SOMEWHAT RESEMBLES A WEAK LA NINA - ESPECIALLY THE WARM WEST PACIFIC - AND RECENT CLIMATE ANOMALIES IN THE VICINITY OF THE U.S. HAVE ALSO BEEN LA NINA-LIKE. SOME MODELS ALSO REACT IN LA NINA-LIKE FASHION TO THE SST ANOMALIES BY WHICH THEY ARE FORCED. MOST STATISTICAL AND DYNAMICAL PREDICTIONS OF NINO 3.4 SSTS INDICATE ANOMALIES AVERAGING VERY NEAR ZERO THROUGHOUT THE CURRENT COOL SEASON WITH WEAK WARM EPISODE (EL NINO) CONDITIONS BECOMING ESTABLISHED BY EARLY SUMMER OF 2002. WHILE IT IS LIKELY THAT EQUATORIAL PACIFIC SSTS NEAR AND JUST WEST OF THE DATE LINE WILL REMAIN ABOVE AVERAGE FOR THE NEXT FEW MONTHS ... THE ANOMALIES ARE EXPECTED TO BE SMALL 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 MONTH-TO-MONTH VARIABILITY... WHICH MAY BE ENHANCED IF MADDEN-JULIAN OSCILLATIONS (MJO)... WHICH ARE CURRENTLY WEAK... BECOME RE- ESTABLISHED OVER THE PACIFIC. CURRENT ATMOSPHERIC AND OCEANIC CONDITIONS NEAR-NORMAL ATMOSPHERIC AND OCEANIC CONDITIONS CONTINUED TO PREVAIL IN THE TROPICAL PACIFIC IN PAST WEEKS. SST ANOMALIES ALONG THE EQUATOR CURRENTLY ARE NEAR +1.0 DEG C AROUND 160E AND RANGE FROM 0.5 TO 1.0 DEG BELOW NOIRMAL IN THE EASTERN PACIFIC EAST OF ABOUT 140W. ABOVE NORMAL OCEAN TEMPERATURES EXTEND FROM THE SURFACE OR NEAR-SURFACE DOWN TO OVER 200 M DEPTH ACROSS MOST OF THE CENTRAL EQUATORIAL PACIFIC OCEAN AND TO 100 M DEPTH AS FAR EAST AS 130W. IT IS THIS EXTENSIVE SUBSURFACE WARMTH OF MODEST MAGNITUDE THAT LEADS SOME FORECAST TOOLS TO PREDICT A SWING TO WEAK WARM ENSO CONDITIONS NEXT YEAR. ENHANCED MJO ACTIVITY HAS BEEN NOTED DURING THE LAST SIX MONTHS... ALTHOUGH IN THE PAST MONTH THE ACTIVITY HAS TEMPORARILY WEAKENED. IT IS EXPECTED TO RESUME SINCE NEAR NEUTRAL ENSO CONDITIONS ARE STILL PRESENT. WITH WARM SSTS FARTHER EAST THAN LAST WINTER THERE IS A BETTER CHANCE THAT MJO WAVES WILL MAKE IT TO THE DATE LINE AND HAVE AN OPPORTUNITY TO IMPACT PRECIPITATION IN THE WESTERN UNITED STATES FROM TIME-TO-TIME IN UPCOMING MONTHS. . . . . . . . . PROGNOSTIC DISCUSSION OF SST FORECASTS NEAR-NEUTRAL ENSO CONDITIONS ARE PREDICTED FOR MUCH OF THE WINTER. MOST DYNAMICAL MODELS (NCEP - SCRIPPS) GRADUALLY PRODUCE POSITIVE NINO 3.4 SST ANOMALIES BEGINNING IN THE LATE SPRING OR EARLY SUMMER 2002. THE CONSTRUCTED ANALOG PREDICTS NEUTRAL OR SLIGHTLY COOL NINO 3.4 SSTS THROUGHOUT NEXT YEAR WHILE CCA PREDICTS MODESTLY ABOVE NORMAL SSTS APPEARING IN EARLY SPRING 2002. A CONSOLIDATION OF THE THREE NCEP TOOLS BASED ON THEIR PAST PERFORMANCE SUGGESTS NEAR-NORMAL CONDITIONS WILL PREVAIL THROUGH THE COMING WINTER WITH GRADUALLY INCREASING POSITIVE NINO 3.4 ANOMALIES THAT REACH AROUND +0.5 DEGREES C BY EARLY NEXT SUMMER. THE CONSOLIDATED TOOL THEN MAINTAINS A MODEST EL NINO OF SLIGHTLY MORE THAN +0.5 DEG C THROUGHOUT THE REST OF 2002. PROGNOSTIC TOOLS USED FOR U.S. TEMPERATURE AND PRECIPITATION OUTLOOK THE STATISTICAL TOOLS ... CCA ... OCN AND SMLR ... WERE CONSULTED AT ALL LEAD TIMES. ENSO-NEUTRAL COMPOSITES WERE CONSIDERED ONLY FOR JFM 2002. THE DATA WERE SUBJECTED TO A RUNNING 9 YEAR FILTER PRIOR TO COMPOSITING IN ORDER TO ISOLATE INTERANNUAL SIGNALS FROM LONGER TIME SCALES WHICH ARE ALREADY IN OCN. DYNAMICAL MODEL FORECASTS FROM NCEP AND OTHER FORECAST CENTERS WERE CONSULTED. MANY OF THE LATEST RUNS - FORCED BY SST ANOMALIES RESEMBLING A WEAK LA NINA - PRODUCED CREDIBLE LA NINA-LIKE PATTERNS SHOWING DRYNESS IN THE SOUTHWEST AND SOUTHEAST FOR THE FIRST COUPLE OF SEASONS. FREQUENTLY THERE IS A WAVE-TRAIN EMANATING FROM THE ABNORMALLY WARM POOL OF WATER IN THE WESTERN TROPICAL PACIFIC WHICH APPEARS TO CAUSE A PERSISTENT PATTERN OVER NORTH AMERICA. THIS PATTERN FAVORS POSITIVE UPPER AIR HEIGHT ANOMALIES OVER THE GULF OF ALASKA AND WEST COAST AND NEGATIVE ANOMALIES OVER EASTERN NORTH AMERICA. THE TEMPERATURE FORECASTS FROM THESE DYNAMICAL MODELS ARE IN OVERALL AGREEMENT WITH SOME OF THE STATISTICAL TOOLS - PARTICULARLY THE ENSO-NEUTRAL COMPOSITES WHICH ALSO PREDICT BELOW NORMAL TEMPERATURES IN THE NORTHEASTERN US. IN PARTS OF THE EAST WE GAVE GREATER WEIGHT TO THESE TOOLS THAN TO THE TREND (OCN) WHICH SHOWS ABOVE NORMAL TEMPERATURES NEARLY EVERYWHERE - LEADING TO FORECASTS OF ONLY WEAKLY ABOVE NORMAL IN THE SOUTHEAST AND BELOW NORMAL IN THE NORTHEASTERN U.S. . . . . . . . . PROGNOSTIC DISCUSSION OF OUTLOOKS - JFM 2002 TO JFM 2003 TEMPERATURE: MOST FORECAST TOOLS INDICATE WARMER-THAN-NORMAL TEMPERATURES FOR JFM 2002 THROUGH JFM 2003 IN THE SOUTHWEST U.S. THIS SIGNAL IS THE STRONGEST TREND SIGNAL ON THE MAP AND THE PROBABILITIES ARE ACCORDINGLY HIGH. MIXED SIGNALS APPEAR OVER ALASKA AND CLIMATOLOGICAL PROBABILITIES ARE OFTEN PREDICTED THERE. ONE MAJOR FACTOR INFLUENCING THE SEASONAL CLIMATE ANOMALIES OVER THE EASTERN U.S. THIS WINTER WILL BE THE PHASE OF THE NAO - WHICH IS NOT PREDICTABLE BEYOND ABOUT 1 OR 2 WEEKS IN ADVANCE. FOR WHAT IT IS WORTH - THE MOST RECENT RUNS OF THE MEDIUM-RANGE MODELS HAVE ALL BEEN PREDICTING A DRAMATIC SHIFT TOWARDS A NEGATIVE NAO BEGINNING JUST AFTER THE MIDDLE OF DECEMBER. IF THIS PATTERN PERSISTS OR RECURS FOR A SIGNIFICANT PART OF THE REMAINDER OF THE WINTER - EVEN MORE EXTENSIVE AREAS OF BELOW NORMAL TEMPERATURES WOULD LIKELY BE OBSERVED THAN THOSE SHOWN ON THE FORECASTS. ENSO-NEUTRAL COMPOSITES INDICATE BELOW NORMAL TEMPERATURES OVER MUCH OF THE CENTRAL AND EASTERN U.S. - WHICH OPPOSES RECENT WARM TRENDS. CHANGES FROM THE PREVIOUS SET OF FORECASTS ARE SMALL - MAINLY IN SHIFTING THE AREA OF PREDICTED BELOW NORMAL TEMPERATURES EASTWARD TO ALLOW FOR THE POSSIBILITY OF ABOVE NORMAL TEMPERATURES THAT SOME OF THE MODELS ARE PREDICTING OVER THE NORTHERN GREAT PLAINS. THE SOUTHEASTERN U.S. IS EXPECTED TO STAY MILD AS TRENDS FOR WARMTH ARE VERY STRONG IN THAT AREA. FROM FMA 2002 THROUGH NEXT FALL CCA AND OCN ARE THE PRIMARY TOOLS. THESE SHOW THE WARM TREND OVER THE WESTERN AND SOUTHERN U.S. DURING THE WARM SEASON AND A COOL TREND IN THE NORTH-CENTRAL U.S. DURING THE LATE SUMMER. FOR DJF 2002-03 AND JFM 2003 THE STRONG PREDOMINANTLY WARM PATTERNS FROM OCN HAVE BEEN ADJUSTED TO CL ACROSS THE SOUTH AS A POTENTIAL EL NINO HAS STRONGER EFFECTS DURING THE COLD SEASON IN THIS REGION AND THE WARM EVENT COMPOSITES FAVOR NORMAL TO SOMEWHAT BELOW NORMAL TEMPERATURES. . . . . . . . . . PRECIPITATION: CCA AND OCN PREDICT ABOVE-MEDIAN PRECIPITATION OVER TEXAS FOR JFM. SOME OF THE COUPLED MODELS ALSO HAD ABOVE-MEDIAN IN THE INTERIOR SOUTHWEST - AND MORE CONSISTENTLY PREDICT SUB-MEDIAN RAINFALL OVER FLORIDA AND MUCH OF CALIFORNIA FOR THE FIRST FEW SEASONS. A DRY SOUTHEAST IS ALSO A WEAK SIGNAL FROM THE NEUTRAL ENSO COMPOSITES. WHILE MJO ACTIVITY IS EXPECTED TO BECOME STRONG AGAIN DURING THE COLD SEASON AND SUCH ACTIVITY CAN BE ASSOCIATED WITH HEAVY PRECIPITATION EVENTS OVER THE PACIFIC NORTHWEST - THE TOOLS CURRENTLY GIVE MIXED INDICATIONS IN THAT REGION SO CL IS PREDICTED THERE. ODDS FOR ABOVE-MEDIAN PRECIPITATION INCREASE IN THE NORTHWEST IN AMJ AND MJJ DUE TO LONG-TERM TRENDS. UNTIL NEXT WINTER - BEYOND MJJ ONLY A DRY AREA OVER THE GREAT BASIN DURING JAS AND A WET AREA OVER FLORIDA DURING LATE SUMMER AND EARLY FALL APPEAR TO BE SIGNIFICANT AND HAVE BEEN RELIABLE ENOUGH IN RECENT YEARS TO BE INCLUDED IN THE FORECASTS. AT LEAST FOR NOW - THE ANTICIPATED EARLY SUMMER DEVELOPMENT OF WEAK EL NINO CONDITIONS IS NOT EXPECTED TO APPRECIABLY SUPPRESS TOPICAL ACTIVITY IN THE ATLANTIC BASIN. NEXT YEAR - DJF 2002-03 AND JFM 2003 HAVE EXTENSIVE AREAS OF ABOVE MEDIAN PRECIPITATION WITH MODEST PROBABILITIES ACROSS THE SOUTHERN PART OF THE NATION DUE TO EXPECTED EL NINO INFLUENCES. FORECAST DRYNESS CENTERED OVER THE NORTHERN ROCKIES IS FROM BOTH OCN AND EL NINO COMPOSITES. THERE ARE NO RELIABLE FORECAST INDICATIONS FOR ALASKA PRECIPITATION TO DEPART FROM CLIMATOLOGICAL PROBABILITIES DURING ANY OF THE LEADS AT THIS TIME. FORECASTERS: A.J. WAGNER AND M. HALPERT 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 JANUARY 17 2002. 1971-2000 BASE PERIOD MEANS WERE IMPLEMENTED EFFECTIVE WITH THE MAY 17 2001 FORECAST RELEASE. NNNN NNNN