PROGNOSTIC DISCUSSION FOR LONG-LEAD SEASONAL OUTLOOKS NWS CLIMATE PREDICTION CENTER CAMP SPRINGS MD 830AM EST THURSDAY DEC 16 2010 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. IMPACTS OF THESE EVENTS ARE SUMMARIZED BY SEPARATING 3-MONTH OBSERVATIONS FROM 3 OR MORE DECADES INTO EL NINO, NEUTRAL, AND LA NINA SETS, AVERAGING EACH SEPARATELY, AND THEN COMPUTING ANOMALIES. THESE ARE CALLED "ENSO COMPOSITES", AND ARE USED TO SUBJECTIVELY MODIFY THE FORECAST. 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. 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) CONSOLIDATION (CON) - AN OBJECTIVE, SKILL AND SPREAD-WEIGHTED 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. MODERATE TO STRONG LA NINA CONDITIONS CONTINUE IN THE TROPICAL PACIFIC OCEAN. SEA SURFACE TEMPERATURES (SSTS) IN THE EQUATORIAL PACIFIC OCEAN ARE BELOW AVERAGE FROM AROUND 160E TO THE SOUTH AMERICAN COAST, WITH SSTS BETWEEN 1 AND 3 DEGREES C BELOW NORMAL IN MOST AREAS. SSTS ARE BELOW NORMAL IN THE EASTERN PACIFIC OCEAN BETWEEN 20N AND 20S WITH BELOW NORMAL COASTAL SSTS EXTENDING JUST ABOUT THE FULL LENGTH OF THE PACIFIC COASTS OF NORTH AND SOUTH AMERICA. THIS VERY LARGE AREA OF ANOMALOUSLY COOL SSTS HAS SIGNIFICANT IMPACT ON THE LARGE SCALE ATMOSPHERIC CIRCULATION THROUGHOUT THE TROPICAL PACIFIC REGION, WHICH, IN TURN, IS EXPECTED TO CONSIDERABLY INFLUENCE THE MEAN ATMOSPHERIC CIRCULATION PATTERNS OVER NORTH AMERICA. SUB-SURFACE OCEAN TEMPERATURES ARE ALSO WELL BELOW AVERAGE IN THE EQUATORIAL EASTERN PACIFIC TO OVER 200 METERS DEPTH, STRONGLY FAVORING A CONTINUATION OF LA NINA CONDITIONS INTO AT LEAST THE SPRING OF 2011. FORECASTS FROM MOST SST PREDICTION MODELS SUPPORT THIS CONCLUSION, WITH SST ANOMALIES PREDICTED TO GRADUALLY DIMINISH INTO THE EARLY SUMMER MONTHS. THE TEMPERATURE OUTLOOK FOR JFM 2011 REFLECTS TYPICAL WINTER LA NINA CONDITIONS AND FAVORS BELOW AVERAGE TEMPERATURES OVER CENTRAL AND SOUTHERN ALASKA, ALONG THE NORTHERN PORTION OF THE CONUS FROM WASHINGTON STATE TO THE UPPER GREAT LAKES AND ALONG THE ENTIRE WEST COAST. THE CHANCES FOR ABOVE AVERAGE MEAN TEMPERATURES ARE ENHANCED FROM THE SOUTHWEST CONUS AND THE SOUTHERN ROCKIES TO THE GULF COAST STATES. THE SEASONAL PRECIPITATION OUTLOOK FOR JFM 2011 FAVORS ABOVE-MEDIAN PRECIPITATION FOR PARTS OF FAR NORTHERN CALIFORNIA, THE PACIFIC NORTHWEST, THE NORTHERN ROCKY MOUNTAINS, NORTHERN GREAT PLAINS AND THE UPPER GREAT LAKES. ABOVE MEDIAN PRECIPITATION AMOUNTS ARE ALSO FAVORED FROM THE CENTRAL MISSISSIPPI VALLEY NORTHEASTWARD TO THE LOWER GREAT LAKES AND PARTS OF NEW ENGLAND. THE CHANCES OF BELOW-MEDIAN PRECIPITATION AMOUNTS ARE ENHANCED FROM SOUTHERN CALIFORNIA TO WESTERN TEXAS, AND ALSO IN PARTS OF THE GULF COAST AND THE SOUTHEASTERN U.S. THIS PRECIPITATION PATTERN REFLECTS THE WEAKER THAN AVERAGE SOUTHERN UPPER LEVEL JET STREAM TOGETHER WITH AN ACTIVE NORTHERN JET THAT IS USUALLY OBSERVED IN LA NINA WINTERS. LA NINA COMPOSITES AND CFS FORECASTS SLIGHTLY FAVOR BELOW MEDIAN PRECIPITATION ALONG ALASKA'S SOUTHERN COAST. IN LOCATIONS WHERE THE LIKELIHOODS OF SEASONAL MEAN TEMPERATURES AND SEASONAL PRECIPITATION AMOUNTS ARE SIMILAR TO THE CLIMATOLOGICAL PROBABILITIES, EQUAL CHANCES OF BELOW, NEAR, AND ABOVE AVERAGE TEMPERATURE AND PRECIPITATION ARE INDICATED. 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 OCEAN TEMPERATURES IN THE CENTRAL AND EASTERN TROPICAL PACIFIC REMAINED FAIRLY STEADY IN THE MONTH OF NOVEMBER AND EARLY DECEMBER. NEGATIVE SEA SURFACE TEMPERATURE (SST) ANOMALIES OF AT LEAST -1.0 C EXTEND ALONG THE EQUATOR FROM ABOUT 160E TO THE SOUTH AMERICAN COAST IN EARLY DECEMBER. THE SUBSURFACE HEAT CONTENT (AVERAGE TEMPERATURES IN THE UPPER 300M OF THE OCEAN) INDICATES A LARGE VOLUME OF WATER WITH BELOW NORMAL TEMPERATURES, WITH NEGATIVE ANOMALIES TO OVER 200 METERS DEPTH BETWEEN ABOUT 170E AND THE SOUTH AMERICAN COAST. BELOW NORMAL SSTS EXTEND TO 20 DEGREES NORTH AND SOUTH LATITUDE IN MUCH OF THE EASTERN PACIFIC OCEAN, AND EXPAND IN THE FAR EASTERN PACIFIC TO ENCOMPASS THE ENTIRE PACIFIC COASTS OF NORTH AND SOUTH AMERICA. ATMOSPHERIC CONDITIONS THROUGHOUT THE TROPICAL PACIFIC OCEAN ARE CONSISTENT WITH THESE LARGE SCALE SST ANOMALIES, AND INCLUDE: SUPPRESSED CONVECTION OVER THE WESTERN AND CENTRAL EQUATORIAL PACIFIC, UNUSUALLY STRONG LOW-LEVEL EASTERLY WINDS, AND STRONG UPPER-LEVEL WESTERLY WINDS OVER THE WESTERN AND CENTRAL EQUATORIAL PACIFIC. THESE INDICATORS SUGGEST MODERATE TO STRONG LA NINA CONDITIONS. THE AREA OF ENHANCED CONVECTION NORMALLY OVER INDONESIA DURING LA NINA EVENTS HAS BEEN DISPLACED SLIGHTLY WESTWARD IN LATE NOVEMBER AND EARLY DECEMBER COMPARED TO ITS USUAL POSITION, PERHAPS REFLECTING THE LARGE EXTENT OF BELOW NORMAL EQUATORIAL SSTS THAT EXTEND TO NEAR THE NORTHERN COAST OF NEW GUINEA. PROGNOSTIC DISCUSSION OF SST FORECASTS STATISTICAL AND DYNAMICAL MODELS PREDICT NEGATIVE SST ANOMALIES TO CONTINUE INTO THE SPRING OF 2011. BIAS-CORRECTED SST FORECASTS FROM THE NCEP CLIMATE FORECAST SYSTEM(CFS) INDICATE THAT THE NINO 3.4 ANOMALY WILL SLOWLY DIMINISH FROM THEIR CURRENT LEVELS NEAR -1.5 C TO AROUND -1.0 C BY THE FMA SEASON AND REMAIN FAIRLY STEADY AFTER THAT INTO THE SUMMER SEASON. MOST STATISTICAL MODELS FOLLOW THE CFS SOLUTION THROUGH THE EARLY PART OF 2011 BUT PREDICT SST ANOMALIES TO CONTINUE TO DIMINISH, WITH NEAR NORMAL SSTS PREDICTED BY THE SUMMER. THE HISTORICAL RECORD SHOWS A FAIRLY EVEN MIX OF MULTI-YEAR AND SINGLE YEAR LA NINA EVENTS, SO AT THIS POINT THERE ARE NO STRONG INDICATIONS OF THE ENSO STATE PAST MID 2011. A CONSOLIDATION FORECAST OF THE CFS, A CONSTRUCTED ANALOG TOOL, THE MARKOV MODEL AND THE CCA FORECASTS FOR NINO 3.4 SSTS SHOWS ANOMALIES BELOW -.5 C CONTINUING TO AROUND AMJ 2011, SUGGESTING CONTINUED LA NINA CONDITIONS INTO THE LATE SPRING. THE CONSOLIDATION TOOL FORECAST INDICATES THAT SSTS ANOMALIES CONTINUE TO DIMINISH, FAVORING ENSO NEUTRAL CONDITIONS BY MID 2011. PROGNOSTIC TOOLS USED FOR U.S. TEMPERATURE AND PRECIPITATION OUTLOOKS MOST TOOLS PRODUCED FORECASTS CONSISTENT WITH LA NINA COMPOSITES FOR LATE WINTER AND SPRING. THE OUTLOOKS FOR JFM THROUGH AMJ 2011 WERE HEAVILY INFLUENCED BY LA NINA COMPOSITES. THE CFS TOOL IN PARTICULAR WAS EMPHASIZED FOR THE OUTLOOKS THROUGH MAM 2011. THE PROBABILITIES FOR ABOVE NORMAL TEMPERATURES IN THE EASTERN CONUS IN JFM 2011 WERE REDUCED FROM VALUES PREDICTED FOR THAT SEASON ON LAST MONTH'S OUTLOOK PRIMARILY DUE TO INCREASED CHANCES FOR NEGATIVE ARCTIC OSCILLATION (AO) IMPLIED BY THE STRONGLY NEGATIVE AO OBSERVED SO FAR THIS MONTH, AND FORECAST TO CONTINUE THROUGH LATE DECEMBER. PAST YEARS WITH SIGNIFICANTLY NEGATIVE MONTHLY MEAN AO VALUES IN NOVEMBER AND DECEMBER SHOW THE AO TO HAVE A SLIGHT DEGREE OF PERSISTENCE INTO THE EARLY MONTHS OF THE FOLLOWING YEAR. OF 20 CASES SINCE 1950 WHERE THE NOVEMBER-DECEMBER MEAN AO WAS IN THE LOWER THIRD OF THE CLIMATOLOGICAL DISTRIBUTION, 45 PERCENT MAINTAINED A SIGNIFICANTLY NEGATIVE 3-MONTH AVERAGE AO FOR JFM THE FOLLOWING YEAR. THIS IS SLIGHTLY MORE THAN THE 33 PERCENT THAT WOULD BE EXPECTED IF AO VALUES FOR JFM WERE INDEPENDENT OF THE VALUES IN THE PREVIOUS FALL. LA NINA IMPACTS MAY EXTEND INTO THE LATE SPRING DUE TO THE SOIL MOISTURE ANOMALIES CAUSED BY WINTERTIME PRECIPITATION ANOMALIES ASSOCIATED WITH LA NINA. THIS PRIMARILY INCREASES THE LIKELIHOOD OF ABOVE NORMAL TEMPERATURES AND DRIER THAN AVERAGE CONDITIONS IN THE SOUTHERN PART OF THE COUNTRY. THE OUTLOOKS FOR MJJ 2011 AND BEYOND ARE BASED ON THE CONSOLIDATION TOOL WHICH IS PRIMARILY INFLUENCED AT THOSE LEADS BY TRENDS RELATED TO DECADAL VARIABILITY IN THE LONG TERM CLIMATE STATE. PROGNOSTIC DISCUSSION OF OUTLOOKS - JFM 2011 TO JFM 2012 TEMPERATURE THE 3-MONTH TEMPERATURE OUTLOOKS FOR JFM THROUGH AMJ 2011 PRIMARILY REFLECT EXPECTED LA NINA IMPACTS. PROBABILITIES OF BELOW NORMAL TEMPERATURES ARE ENHANCED IN MOST OF ALASKA, THE PACIFIC NORTHWEST, THE NORTHERN ROCKIES, EXTENDING EASTWARD INTO THE NORTHERN PLAINS AND THE WESTERN GREAT LAKES DURING WINTER AND SPRING. PROBABILITIES OF ABOVE NORMAL TEMPERATURES ARE ENHANCED IN MUCH OF THE CENTRAL AND SOUTHERN U.S. THE OUTLOOKS FOR MJJ 2011 THROUGH JFM 2012 PRIMARILY REFLECT DECADAL OR LONGER VARIABILITY IN THE LONG TERM CLIMATE STATE FAVORING ABOVE NORMAL TEMPERATURES FOR MUCH OF THE WEST. AN ELEVATED CHANCE OF BELOW NORMAL TEMPERATURES IN THE NORTHERN PLAINS IN MJJ 2011 REFLECTS RECENT LONG TERM VARIABILITY IN THIS REGION. ABOVE NORMAL TEMPERATURES ARE ALSO FAVORED FOR ALASKA IN THESE LATER LEADS WHERE AND WHEN WARMING TRENDS HAVE BEEN RELIABLE INDICATORS OF SEASONAL MEAN TEMPERATURES. PRECIPITATION THE OUTLOOKS FOR JFM THROUGH AMJ 2011 SHOW THE EXPECTED IMPACT OF CIRCULATION ANOMALIES ASSOCIATED WITH LA NINA. THE PROBABILITIES OF ABOVE MEDIAN PRECIPITATION ARE ENHANCED FROM THE PACIFIC NORTHWEST THROUGH TO THE GREAT LAKES REGION AND IN THE OHIO AND TENNESSEE VALLEYS IN JFM. THIS SIGNAL GRADUALLY DIMINISHES IN LATER SEASONS, DISAPPEARING BY AMJ. DRY CONDITIONS PREDICTED FOR THE SOUTHWEST AND SOUTHEAST DURING THIS PERIOD RELFECT LA NINA AS WELL. LA NINA COMPOSITES AND THE CFS FORECAST SLIGHTLY FAVOR BELOW MEDIAN PRECIPITATION ALONG PARTS OF ALASKA'S SOUTH COAST FOR JFM 2011. IN SPITE OF THE FORECAST WEAKENING OF LA NINA INTO THE SPRING, SOIL MOISTURE ANOMALIES IN REGIONS OF EXPECTED DEFICIENT WINTERTIME PRECIPITATION MAY DIMINISH LOCAL EVAPORATIVE MOISTURE SOURCES AND ELEVATE THE CHANCES FOR CONTINUED DRY CONDITIONS LATER IN THE SPRING. THUS THE FORECAST FOR ENHANCED CHANCE OF BELOW MEDIAN PRECIPITATION WAS EXTENDED LATER INTO SPRING THAN INDICATED ON THE PREVIOUS OUTLOOK DUE TO HIGHER CONFIDENCE THIS MONTH OF THE LA NINA INFLUENCE ON COOL SEASON PRECIPITATION. DECADAL TRENDS LEAD TO ENHANCED CHANCES OF BELOW MEDIAN PRECIPITATION IN THE PACIFIC NORTHWEST AND OF ABOVE MEDIAN PRECIPITATION IN FLORIDA AND THE CENTRAL PLAINS DURING LATE SUMMER AND EARLY FALL OF 2011. MOST OF THE OUTLOOKS BEYOND SON 2011 SHOW EQUAL CHANCES BECAUSE OF A LACK OF SKILLFUL INDICATORS, EXCEPT FOR ENHANCED CHANCES FOR BELOW MEDIAN PRECIPITATION IN THE SOUTHEAST U.S. DUE TO LONG TERM TRENDS IN JFM 2012. 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 JAN 20 2011 1971-2000 BASE PERIOD MEANS WERE IMPLEMENTED EFFECTIVE WITH THE MAY 17, 2001 FORECAST RELEASE. $$