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PROGNOSTIC DISCUSSION FOR LONG-LEAD SEASONAL OUTLOOKS NWS CLIMATE PREDICTION CENTER CAMP SPRINGS MD 830 AM EST THU DEC 18 2008 SUMMARY OF THE OUTLOOK FOR NON-TECHNICAL USERS THE MAIN FACTORS WHICH USUALLY INFLUENCE THE SEASONAL CLIMATE OUTLOOK INCLUDE: 1) EL NINO AND LA NINA - WHICH COMPRISE EL NINO/SOUTHERN OSCILLATION OR ENSO. 2) TRENDS - APPROXIMATED BY THE OCN TOOL AS THE DIFFERENCE BETWEEN THE MOST RECENT 10-YEAR MEAN OF TEMPERATURE OR 15-YEAR MEAN OF PRECIPITATION FOR A GIVEN LOCATION AND TIME OF YEAR AND THE 30-YEAR CLIMATOLOGY PERIOD (CURRENTLY 1971-2000). 3) THE TROPICAL 30-60 DAY OSCILLATION - SOMETIMES CALLED MADDEN JULIAN OSCILLATION (MJO) - AFFECTS CLIMATE VARIABILITY WITHIN SEASONS. 4) THE NORTH ATLANTIC OSCILLATION (NAO) AND THE PACIFIC NORTH AMERICAN (PNA) PATTERNS - WHICH AFFECT THE TEMPERATURE ANOMALY PATTERN ESPECIALLY DURING THE COLD SEASONS. THESE PHENOMENA ARE CURRENTLY KNOWN TO BE PREDICTABLE ONLY OVER A WEEK OR SO. 5) THE PACIFIC DECADAL OSCILLATION (PDO) - AN ENSO-LIKE PATTERN OF CLIMATE VARIABILITY AFFECTING BOTH THE TROPICS AND THE NORTH PACIFIC AND NORTH AMERICAN REGIONS, BUT WHICH VARIES ON A MUCH LONGER TIME-SCALE THAN ENSO. 6) PERSISTENTLY DRY OR WET SOILS IN THE SUMMER AND SNOW AND ICE COVER ANOMALIES IN THE WINTER. THESE FACTORS TEND TO PERSIST FOR LONG PERIODS AND ACT AS A KIND OF MEMORY IN THE CLIMATE SYSTEM. THE MAIN FORECAST TOOLS ARE AS FOLLOWS: 7) STATISTICAL FORECAST TOOLS - CANONICAL CORRELATION ANALYSIS (CCA), SCREENING MULTIPLE LINEAR REGRESSION (SMLR), CONSTRUCTED ANALOGUE (CA) AND ENSEMBLE CCA (ECCA). 8) DYNAMICAL FORECAST MODELS - INCLUDING THE NCEP CLIMATE FORECAST SYSTEM (CFS). 9) AN OBJECTIVE CONSOLIDATION (ABBREVIATED CON IN THE TEXT) OF THE OCN, CCA, SMLR, ECCA, AND CFS FORECASTS IS USED AS A FIRST GUESS IN PREPARING THE FORECAST MAPS. THIS TECHNIQUE MAKES OPTIMUM USE OF THE KNOWN SKILL OF OUR FORECAST TOOLS. OCEANIC AND ATMOSPHERIC INDICATORS CONTINUE TO SUGGEST ENSO-NEUTRAL CONDITIONS PREVAILED FROM LATE NOVEMBER THROUGH EARLY DECEMBER 2008, ALTHOUGH IN RECENT WEEKS CONDITIONS IN THE EQUATORIAL PACIFIC OCEAN HAVE BECOME SUGGESTIVE OF LA NINA CONDITIONS. SEA SURFACE TEMPERATURES (SSTS) ARE BELOW NORMAL ALONG THE EQUATOR THROUGHOUT MOST OF THE EASTERN PACIFIC OCEAN WITH WATER TEMPERATURES JUST UNDER THE SURFACE SUBSTANTIALLY BELOW NORMAL. SST FORECASTING TOOLS ARE FAIRLY EVENLY SPLIT BETWEEN CONTINUING ENSO-NEUTRAL CONDITIONS AND THE DEVELOPMENT OF A WEAK LA NINA IN EARLY 2009. THESE CURRENT OBSERVATIONS TOGETHER WITH THE SST FORECAST SUGGEST THAT THE OCEAN-ATMOSPHERE STATE WILL BE ON THE BOARDER LINE BETWEEN NEUTRAL AND WEAK LA NINA CONDITIONS IN THE NEXT FEW MONTHS. THE TEMPERATURE OUTLOOK FOR JFM 2009 CALLS FOR ABOVE AVERAGE TEMPERATURES FROM THE INTERIOR SOUTHWESTERN U.S. EXTENDING EASTWARD TO INCLUDE TEXAS, THE SOUTHERN GREAT PLAINS, AND MUCH OF THE EASTERN U.S. EXCEPT FOR THE NORTHEAST. BELOW NORMAL TEMPERATURES ARE FAVORED IN THE PACIFIC NORTHWEST, PORTIONS OF THE NORTHERN ROCKIES AND MOST OF MONTANA. BELOW NORMAL TEMPERATURES ARE ALSO EXPECTED IN PARTS OF SOUTHERN ALASKA. THIS TEMPERATURE PATTERN IS SUPPORTED BY A RANGE OF NUMERICAL CLIMATE MODELS AND STATISTICAL TOOLS AND IS TYPICAL OF TEMPERATURES ASSOCIATED WITH LA NINA. ABOVE NORMAL TEMPERATURES ARE EXPECTED FOR NORTHERN ALASKA DUE TO LONG TERM TRENDS. ELSEWHERE, EQUAL CHANCES OF BELOW-, NEAR-, AND ABOVE AVERAGE TEMPERATURES ARE PREDICTED. THERE IS AN ENHANCED LIKELIHOOD OF BELOW MEDIAN PRECIPITATION AMOUNTS FOR JFM 2009 ACROSS MUCH OF THE SOUTHERN CONTIGUOUS U.S. EXCEPT FOR PORTIONS OF THE CENTRAL GULF OF MEXICO COAST AS INDICATED MAINLY BY CFS DYNAMICAL MODEL PREDICTIONS AND THE CONSOLIDATION FORECAST. ABOVE MEDIAN PRECIPITATION AMOUNTS ARE EXPECTED FROM THE SOUTHERN GREAT PLAINS TO THE OHIO VALLEY, DUE TO A COMBINATION OF LONG TERM TRENDS, NEAR OKLAHOMA, AND CFS FORECASTS IN THE OHIO VALLEY. BASIS AND SUMMARY OF THE CURRENT LONG-LEAD OUTLOOKS NOTE: FOR GRAPHICAL DISPLAYS OF THE FORECAST TOOLS DISCUSSED BELOW SEE: HTTP://WWW.CPC.NCEP.NOAA.GOV/PRODUCTS/PREDICTIONS/90DAY/TOOLS/BRIEFING CURRENT ATMOSPHERIC AND OCEANIC CONDITIONS ENSO-NEUTRAL CONDITIONS CONTINUED BETWEEN MID-NOVEMBER AND MID-DECEMBER, 2008, ALTHOUGH OCEANIC AND ATMOSPHERIC INDICATORS HAVE BECOME MORE SUGGESTIVE OF LA NINA CONDITIONS IN THE RECENT FEW WEEKS. SSTS ALONG THE EQUATOR ARE NOW MORE THAN .5 DEGREES C BELOW NORMAL FROM THE DATE LINE TO ABOUT 120W LONGITUDE, WITH ANOMALIES GENERALLY BETWEEN 0 AND -1.0 C FROM 120W TO THE SOUTH AMERICAN COAST. THE LATEST WEEKLY SST INDEX VALUES FOR THE NINO REGIONS, FROM WEST TO EAST ARE -0.5 IN NINO 4, -0.7 IN NINO 3.4, -0.5 IN NINO 3, AND -0.6 IN THE NINO 1+2 REGIONS. THE SUBSURFACE OCEANIC HEAT CONTENT ANOMALIES IN THE EASTERN PACIFIC OCEAN (THE AVERAGE WATER TEMPERATURES IN THE UPPER 300M) HAVE BECOME INCREASINGLY NEGATIVE IN THE LAST MONTH AND ARE NOW AROUND -1.0 C. LOW-LEVEL EASTERLY WIND ANOMALIES COUPLED WITH WESTERLY WIND ANOMALIES AT UPPER LEVELS HAVE STRENGTHENED IN RECENT WEEKS AND LARGE SCALE CONVECTION CONTINUES TO BE ENHANCED IN THE WESTERN PACIFIC NEAR INDONESIA AND SUPPRESSED IN THE CENTRAL PACIFIC NEAR THE DATELINE. PROGNOSTIC DISCUSSION OF SST FORECASTS MOST DYNAMICAL AND STATISTICAL SST FORECASTS FOR THE NINO 3.4 REGION PREDICT SST ANOMALIES IN THE RANGE BETWEEN -0.1 AND -0.7 C, INDICATING ENSO-NEUTRAL OR WEAK LA NINA CONDITIONS IN THE NEXT FEW MONTHS. A CONSOLIDATION FORECASTS BASED ON THE CFS AND SEVERAL STATISTICAL TOOLS FOR THE NINO 3.4 SSTS INDICATE THAT NINO 3.4 SSTS WILL DIP BELOW -.5 C FOR THE EARLY PART OF 2009, BUT RETURN TO NEAR NORMAL VALUES SOON THERAFTER, REMAINING SOMEWHAT BELOW NORMAL THROUGH AT LEAST EARLY SUMMER. PROGNOSTIC TOOLS USED FOR U.S. TEMPERATURE AND PRECIPITATION OUTLOOKS THE TEMPERATURE AND PRECIPITATION OUTLOOKS FOR ALL LEAD TIMES ARE BASED HEAVILY ON THE CONSOLIDATION FORECAST (CON), A SKILL-WEIGHTED AND CALIBRATED OBJECTIVE BLEND OF THE CFS, SMLR, OCN, CCA, AND ECCA FORECAST TOOLS. OTHER TOOLS, THE IRI MULTI-MODEL ENSEMBLE FORECASTS BASED ON SEVERAL DYNAMIC CLIMATE MODELS, THE ECPC CLIMATE FORECAST, AND THE CAS TOOL ARE ALSO CONSIDERED AND USED TO ADJUST THE FORECAST. THE CONSOLIDATION FORECAST IS NOT AVAILABLE FOR ALASKA, SO THE FORECAST THERE IS BASED ON A SUBJECTIVE COMBINATION OF CCA, CFS, OCN, AND SMLR FORECASTS. LA NINA COMPOSITES WERE NOT CONSULTED FOR THIS SERIES OF FORECASTS, HOWEVER MOST CLIMATE MODEL PREDICTIONS PREDICT A PATTERN SIMILAR TO LA NINA COMPOSITES IN THE NEXT FEW SEASONS, LENDING SOME SUPPORT TO THE POSSIBILITY THAT THE MARGINAL LA NINA CONDITIONS IN THE TROPICAL PACIFIC MAY HAVE AN INFLUENCE ON NORTH AMERICAN TEMPERATURE AND PRECIPITATION, HENCE THESE MODELS WERE GIVEN SOME ADDITIONAL WEIGHT FROM JFM TO MAM. PROGNOSTIC DISCUSSION OF OUTLOOKS - JFM 2009 TO JFM 2010 TEMPERATURE: THE TEMPERATURE OUTLOOK FOR JFM 2009 CALLS FOR ABOVE AVERAGE TEMPERATURES FROM THE INTERIOR SOUTHWESTERN U.S. EXTENDING EASTWARD TO INCLUDE TEXAS, THE SOUTHERN GREAT PLAINS, AND MUCH OF THE EASTERN U.S. EXCEPT FOR THE NORTHEAST. BELOW NORMAL TEMPERATURES ARE EXPECTED IN THE PACIFIC NORTHWEST, PORTIONS OF THE NORTHERN ROCKIES, MOST OF MONTANA, AND ALSO IN SOUTHERN ALASKA. THIS TEMPERATURE PATTERN IS SUPPORTED BY A RANGE OF NUMERICAL MODELS AND STATISTICAL TOOLS AND IS TYPICAL OF LA NINA WINTERS. ABOVE NORMAL TEMPERATURES ARE EXPECTED FOR NORTHERN ALASKA DUE TO LONG TERM TRENDS. THERE IS A WIDE CONSENSUS AMONG CLIMATE MODELS THAT BELOW NORMAL TEMPERATURES WILL CONTINUE INTO FMA 2009 IN THE PACIFIC NORTHWEST. OTHERWISE, TEMPERATURES FOR OUTLOOKS FROM FMA 2009 THROUGH JFM 2010 ARE MAINLY FROM LONG TERM TRENDS ADJUSTED TO SOME EXTENT BY WEAK SIGNALS FROM THE VARIOUS OTHER TOOLS USED IN THE CONSOLIDATION FORECAST. PRECIPITATION: THERE IS WIDE CONSENSUS FOR BELOW MEDIAN PRECIPITATION AMOUNTS OVER MUCH OF THE SOUTHERN CONUS WITH GREATEST CONFIDENCE NEAR WESTERN TEXAS AND IN FLORIDA. THERE IS SOME SUPPORT FROM LONG TERM TRENDS FOR ABOVE MEDIAN PRECIPITATION NEAR OKLAHOMA. THIS AREA WAS ADJUSTED ON THE BASIS OF CFS FORECASTS WHICH FAVORED DRY CONDITIONS OVER TEXAS AND ABOVE MEDIAN PRECIPITATION AMOUNTS FROM THE MIDDLE MISSISSIPPI VALLEY TO OHIO. DRY CONDITIONS CONTINUE OVER THE SOUTHEAST AND SOUTHERN ROCKIES INTO FMA 2009, DUE MAINLY TO OCN AND CFS FORECASTS. THE CFS FAVORS BELOW MEDIAN PRECIPITATION IN THE SOUTHERN AND CENTRAL ROCKIES FOR MAM AND AMJ 2009. BY MJJ 2009 ENHANCED CHANCES OF BELOW MEDIAN PRECIPITATION APPEAR IN PARTS OF THE NORTHERN GREAT BASIN AND THEN IN THE PACIFIC NORTHWEST BY JJA THROUGH ASO, PRIMARILY REFLECTING LONG TERM TRENDS. THE ABOVE MEDIAN PRECIPITATION AMOUNTS FOR COASTAL AREAS IN THE SOUTHEAST IN JAS THROUGH SON ARE RELATED TO INCREASED TROPICAL ACTIVITY DURING RECENT YEARS. THE CONSOLIDATION FORECAST INDICATES ABOVE MEDIAN PRECIPITATION FOR PARTS OF THE NORTHEASTERN CONUS FOR ASO AND SON 2009. SIGNALS FOR DJF AND JFM 2009-2010 REFLECT TRENDS. THE PRECIPITATION OUTLOOK FOR ALASKA FOR ALL SEASONS IS LEFT AT CLIMATOLOGICAL PROBABILITIES, WITH NO STRONG TRENDS IN PRECIPITATION EVIDENT DURING ANY SEASON. NOTE - AREAS OF UNCERTAINTY THAT FORMERLY WERE LABELED CL (CLIMATOLOGICAL PROBABILITIES) ARE NOW LABELED EC (EQUAL CHANCES). FORECASTER: DAVID UNGER FOR A DESCRIPTION OF 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/90DAY/DISC.HTML (USE LOWER CASE LETTERS) INFORMATION ON THE FORMATION OF SKILL OF THE CAS FORECASTS MAY BE FOUND AT: HTTP://WWW.CPC.NCEP.NOAA.GOV/SOILMST/FORECASTS.HTML (USE LOWERCASE LETTERS) NOTES - THESE CLIMATE OUTLOOKS ARE INTENDED FOR USE PRIOR TO THE START OF THEIR VALID PERIOD. 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 THU JAN 15 2009 1971-2000 BASE PERIOD MEANS WERE IMPLEMENTED EFFECTIVE WITH THE MAY 17, 2001 FORECAST RELEASE. $$
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