PROGNOSTIC DISCUSSION FOR LONG-LEAD SEASONAL OUTLOOKS NWS CLIMATE PREDICTION CENTER CAMP SPRINGS MD 830AM EDT THURSDAY SEP 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) 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. SEA SURFACE TEMPERATURES (SSTS) ALONG THE EQUATOR IN THE EASTERN AND CENTRAL PACIFIC HAVE DECREASED DRAMATICALLY FROM ABOVE NORMAL IN APRIL, TO WELL BELOW NORMAL THROUGH AUGUST 2010. WEEKLY SSTS FOR THE NINO 3.4 REGION (FROM 120 TO 170 DEGREES WEST LONGITUDE AND FROM 5 DEGREES SOUTH TO 5 DEGREES NORTH LATITUDE) HAVE BEEN MORE THAN 1 DEGREES CELSIUS BELOW AVERAGE SINCE THE MIDDLE OF JULY, INDICATING THAT LA NINA HAS STRENGTHENED OVER THE PAST FEW MONTHS. THE OND 2010 TEMPERATURE OUTLOOK FAVORS ABOVE NORMAL SEASONAL MEAN TEMPERATURES IN THE DESERT SOUTHWEST, EXTENDING EASTWARD INTO WEST TEXAS AND MUCH OF THE EASTERN HALF OF THE CONTIGUOUS UNITED STATES EXCEPT IN THE SOUTHEAST AND ALONG THE EAST COAST UP INTO NEW ENGLAND. THE ENHANCED LIKELIHOOD OF ABOVE NORMAL TEMPERATURES PREDICTED IN THE CENTRAL U.S. IS CONSISTENT WITH LA NINA, WHILE LA NINA CONDITIONS AND DECADAL WARMING TRENDS CONTRIBUTE TO THE ENHANCED PROBABILITY OF ABOVE NORMAL TEMPERATURES IN THE SOUTHWEST. ABOVE NORMAL TEMPERATURES ARE ALSO FAVORED FOR NORTHERN ALASKA, WHERE A RELIABLE WARMING TREND HAS BEEN OBSERVED. BELOW AVERAGE TEMPERATURES ARE FAVORED ALONG THE WEST COAST IN ASSOCIATION WITH SSTS THAT HAVE BEEN RUNNING BELOW AVERAGE FOR THE PAST FEW MONTHS. LA NINA CONDITIONS FAVOR ABOVE MEDIAN PRECIPITATION AMOUNTS IN OND FOR THE PACIFIC NORTHWEST AND BELOW MEDIAN PRECIPITATION AMOUNTS ACROSS MUCH OF THE SOUTH FROM THE SOUTHWEST TO THE SOUTHEAST. PROBABILITIES IN THE SOUTHEAST WERE LEFT RATHER MODEST AS A CONTINUING ACTIVE HURRICANE SEASON COULD RESULT IN LANDFALLING TROPICAL CYCLONES DURING OCTOBER OR NOVEMBER. 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 NEGATIVE SEA SURFACE TEMPERATURE (SST) ANOMALIES REACHED AT LEAST -1.0C ACROSS MOST OF THE EQUATORIAL PACIFIC OCEAN EAST OF 165E BY THE END OF AUGUST. ALSO ALL OF THE NINO INDICES COOLED TO BETWEEN –1.3C AND –1.8C BY THE END OF THE MONTH. CONSISTENT WITH THIS EVOLUTION, THE SUBSURFACE HEAT CONTENT (AVERAGE TEMPERATURES IN THE UPPER 300M OF THE OCEAN) DECREASED FURTHER, REFLECTING THE ADDITIONAL COOLING OF SUB-SURFACE WATERS EAST OF THE DATE LINE. ATMOSPHERIC CONDITIONS WERE ALSO CONSISTENT WITH LA NINA DURING THE MONTH. CONVECTION WAS ENHANCED OVER INDONESIA, WHILE REMAINING SUPPRESSED OVER THE WESTERN AND CENTRAL EQUATORIAL PACIFIC. THE PATTERN ALSO FEATURED THE CONTINUATION OF ENHANCED LOW-LEVEL EASTERLY TRADE WINDS AND ANOMALOUS UPPER-LEVEL WESTERLY WINDS OVER THE WESTERN AND CENTRAL EQUATORIAL PACIFIC. COLLECTIVELY, THESE OCEANIC AND ATMOSPHERIC ANOMALIES ARE CONSISTENT WITH A STRENGTHENING LA NINA. PROGNOSTIC DISCUSSION OF SST FORECASTS NEARLY ALL STATISTICAL AND DYNAMICAL MODELS PREDICT NEGATIVE SST ANOMALIES TO CONTINUE THROUGH THE END OF THE YEAR AND INTO NEXT SPRING. THESE FORECASTS ARE SLIGHTLY STRONGER THAN 1 MONTH AGO IN PART BECAUSE OF COLDER INITIAL CONDITIONS IN AUGUST THAN IN JULY. BIAS-CORRECTED SST FORECASTS FROM THE NCEP CLIMATE FORECAST SYSTEM (CFS), A DYNAMICAL COUPLED OCEAN-ATMOSPHERE MODEL, INDICATE THAT THE NINO 3.4 ANOMALY WILL BE NEAR -1.5C FOR SON AND NEAR -2C DURING OND AND NDJ. THE CPC SST CONSOLIDATION FORECAST (AN OBJECTIVE, SKILL-WEIGHTED COMBINATION OF THE CFS AND THREE STATISTICAL SST FORECASTS) PREDICTS ANOMALIES BETWEEN -1.0 AND -1.5 C THROUGH 2010 INTO EARLY 2011. PROGNOSTIC TOOLS USED FOR U.S. TEMPERATURE AND PRECIPITATION OUTLOOKS THE CPC CONSOLIDATION (A SKILL-WEIGHTED AND CALIBRATED-PROBABILITY FORECAST DERIVED FROM THE CFS, SMLR, OCN, ECCA AND CCA FORECAST TOOLS) WAS THE STARTING POINT USED FOR THE SEASONAL TEMPERATURE AND PRECIPITATION OUTLOOKS. TEMPERATURE AND PRECIPITATION COMPOSITES FOR LA NINA CONDITIONS WERE HEAVILY USED TO MODIFY THE CONSOLIDATION FOR THE PERIOD OND 2010 THROUGH THE MAM 2011 OUTLOOK. SOME ADJUSTMENTS HAVE BEEN MADE TO HISTORICAL LA NINA IMPACTS DUE TO DECADAL TEMPERATURE TRENDS. THE CFS TEMPERATURE AND PRECIPITATION FORECASTS CONTRIBUTED TO THE FORECASTS UNTIL MAM 2011. OUTLOOKS FOR JJA 2011 AND BEYOND ARE BASED PRIMARILY ON THE CPC CONSOLIDATION FORECAST WHICH IS DOMINATED BY TEMPERATURE AND PRECIPITATION TRENDS, IF ANY, RELATED TO DECADAL VARIABILITY IN THE LONG TERM CLIMATE STATE. PROGNOSTIC DISCUSSION OF OUTLOOKS - OND 2010 TO OND 2011 TEMPERATURE ABOVE NORMAL TEMPERATURES ARE FAVORED IN OND 2010 FOR LARGE PARTS OF THE LOWER 48 STATES EXCLUDING THE PACIFIC COAST, THE NORTHWEST AND IN THE SOUTHEAST EXTENDING NORTHWARD ALONG THE EAST COAST TO NEW ENGLAND. PROBABILITIES ARE GREATEST IN THE DESERT SOUTHWEST DUE PRIMARILY TO DECADAL TEMPERATURE TRENDS AND LA NINA IMPACTS. BELOW AVERAGE TEMPERATURES ARE FAVORED RIGHT ALONG THE PACIFIC COAST, MAINLY DUE TO THE PERSISTENCE OF BELOW AVERAGE SSTS UP AND DOWN THE COAST. THE OUTLOOKS FOR NDJ 2010-11 THROUGH MAM 2011 PRIMARILY REFLECT EXPECTED LA NINA IMPACTS. THE PROBABILITIES OF BELOW NORMAL TEMPERATURES ARE ENHANCED IN MOST OF ALASKA, THE PACIFIC NORTHWEST, THE NORTHERN ROCKIES, AND EXTENDING EASTWARD INTO THE NORTHERN PLAINS AND THE WESTERN GREAT LAKES DURING THE LATER LEADS. THIS IS SUPPORTED BY TRENDS AS WELL FOR THE LATER LEADS. THE PROBABILITIES OF ABOVE NORMAL TEMPERATURES ARE ENHANCED IN MUCH OF THE SOUTHERN U.S. BY THE EXPECTATIONS OF A MODERATE TO STRONG LA NINA. THE OUTLOOKS FOR AMJ THROUGH OND 2011 PRIMARILY REFLECT DECADAL 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 AMJ AND MJJ 2011 REFLECTS RECENT DECADAL 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 PRECIPITATION OUTLOOK FOR OND 2010 INDICATES INCREASED CHANCES FOR ABOVE MEDIAN PRECIPITATION FOR AREAS IN THE NORTHWEST DUE TO LA NINA IMPACTS. LA NINA ALSO FAVORS BELOW MEDIAN RAINFALL IN MUCH OF THE SOUTH, BUT THIS CAN BE CONTRADICTED IN THE FALL BY AN ACTIVE HURRICANE SEASON. THE PROBABILITY OF BELOW MEDIAN PRECIPITATION IS ENHANCED ACROSS MUCH OF THE SOUTH, ALTHOUGH PROBABILITIES IN THE SOUTHEAST ARE LOWERED DUE TO THE THREAT OF LANDFALLING HURRICANES DURING THE EARLY PART OF THE SEASON. THE OUTLOOKS FOR NDJ 2010-11 THROUGH MAM 2011 SHOW THE EXPECTED IMPACT OF LA NINA CONDITIONS ON PRECIPITATION. THIS INCLUDES ENHANCED PROBABILITIES OF ABOVE MEDIAN PRECIPITATION IN THE PACIFIC NORTHWEST AND NORTHERN ROCKIES IN THE FALL AND WINTER SEASONS AND IN THE OHIO AND TENNESSEE VALLEYS DURING WINTER. IN ADDITION, PROBABILITIES OF BELOW MEDIAN PRECIPITATION AMOUNTS ARE ENHANCED ACROSS MOST OF THE SOUTHERN U.S. DURING THIS ENTIRE PERIOD. BOTH THE IMPACT OF LA NINA CONDITIONS AND THE CONFIDENCE IN ENSO PREDICTIONS DECREASE IN THE SPRING OF 2011 SUCH THAT THERE IS NO SIGNAL FOR PRECIPITATION ANOMALIES FOR AMJ AND MJJ 2011.. 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 IN A FEW OF THE LATER LEADS. NOTE - AREAS OF UNCERTAINTY THAT FORMERLY WERE LABELED CL (CLIMATOLOGICAL PROBABILITIES) ARE NOW LABELED EC (EQUAL CHANCES). FORECASTER: MIKE HALPERT 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 OCT 21 2010 1971-2000 BASE PERIOD MEANS WERE IMPLEMENTED EFFECTIVE WITH THE MAY 17, 2001 FORECAST RELEASE. $$