PROGNOSTIC DISCUSSION FOR LONG-LEAD SEASONAL OUTLOOKS NWS CLIMATE PREDICTION CENTER CAMP SPRINGS MD 300PM EDT THURSDAY AUG 19 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 EAST-CENTRAL PACIFIC HAVE DECREASED DRAMATICALLY FROM ABOVE NORMAL IN APRIL, TO WELL BELOW NORMAL THROUGH JULY 2010. THE WEEKLY SST DEPARTURE FROM NORMAL FOR THE NINO 3.4 REGION (FROM 120 TO 170 DEGREES WEST LONGITUDE AND FROM 5 DEGREES SOUTH TO 5 DEGREES NORTH LATITUDE)HAS BEEN IN EXCESS OF 1 DEGREES CELSIUS SINCE THE MIDDLE OF JULY. THIS INDICATES THAT THE ENSO STATE HAS CHANGED FROM EL NINO TO LA NINA IN A MATTER OF MONTHS. THE SON 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. ABOVE NORMAL TEMPERATURES IN THE EASTERN U.S. ARE CONSISTENT WITH THE DEVELOPING LA NINA AND WITH DECADAL TEMPERATURE TRENDS IN PARTS OF THE NORTHEAST AS WELL, 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. LA NINA CONDITIONS FAVOR ABOVE MEDIAN PRECIPITATION AMOUNTS IN SON FOR THE NORTHWEST AND BELOW MEDIAN PRECIPITATION AMOUNTS IN THE SOUTHWEST AND THE CENTRAL MISSISSIPPI VALLEY. THE CHANCES OF ABOVE MEDIAN PRECIPITATION AMOUNTS ARE ALSO ENHANCED OVER PARTS OF THE CENTRAL AND NORTHERN PLAINS DUE TO TRENDS. 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 EQUATORIAL SST ANOMALIES ARE NOW PREDOMINANTLY NEGATIVE FROM ABOUT 160E TO THE SOUTH AMERICAN COAST, AN UNUSUALLY LARGE AREA EVEN FOR A COLD EVENT. THE MOST RECENT 7-DAY MEAN SEA SURFACE TEMPERATURE ANOMALIES ARE BELOW -1.0 DEGREE C ALONG THE EQUATOR EAST OF 180W LONGITUDE. THESE OBSERVATIONS ARE CONSISTENT WITH LA NINA CONDITIONS. ATMOSPHERIC CONDITIONS OVER THE TROPICAL PACIFIC ALSO APPEAR TO BE TYPICAL FOR LA NINA CONDITIONS, CHARACTERIZED BY ABOVE NORMAL EASTERLY TRADE WINDS WHICH ARE CURRENTLY OBSERVED FROM THE DATE LINE TO THE MARITIME CONTINENT, SUPPRESSED CONVECTION CURRENTLY SEEN OVER MUCH OF THE PACIFIC, AND ENHANCED CONVECTION CURRENTLY OVER THE EASTERN INDIAN OCEAN. NOTE THAT AN OFFICIAL CLASSIFICATION OF A LA NINA EVENT REQUIRES THREE MONTH MEAN ATMOSPHERE AND OCEAN CONDITIONS CONSISTENT WITH LA NINA TO PERSIST THROUGH SEVERAL SEASONS. THERE IS CURRENTLY A DEEP LAYER OF BELOW NORMAL OCEAN TEMPERATURES EXTENDING TO 250 METERS DEPTH IN THE CENTRAL PACIFIC OCEAN WITH NEGATIVE ANOMALIES BELOW -2 DEGREES C FROM THE SURFACE TO A DEPTH GREATER THAN 100 METERS ACROSS THE EASTERN PACIFIC. SOME OF THE SUBSURFACE ANOMALIES HAVE BEEN RECHARGED BY PERSISTENT EASTERLY WIND ANOMALIES IN THE WEST PACIFIC. THE PRESENCE OF BELOW NORMAL TEMPERATURES AT DEPTH OFTEN PRECEDE SUSTAINED COOLING OF THE SURFACE, MAKING IT UNLIKELY FOR SST ANOMALIES TO RETURN TO POSITIVE VALUES IN THE NEXT COUPLE MONTHS. 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 STRONG THAN 1 MONTH AGO IN PART BECAUSE OF COLDER INITIAL CONDITIONS IN JULY THAN IN JUNE. BIAS-CORRECTED SST FORECASTS FROM THE NCEP CLIMATE FORECAST SYSTEM (CFS), A DYNAMICAL COUPLED OCEAN-ATMOSPHERE MODEL, INDICATE THAT THE NINO 3.4 ANOMALY BE AROUND -1 C FOR SON AND NEAR -2C BY THE END OF THE YEAR. THE CPC SST CONSOLIDATION FORECAST (AN OBJECTIVE, SKILL-WEIGHTED COMBINATION OF THE CFS AND THREE STATISTICAL SST FORECASTS) PREDICTS AN ANOMALY AROUND -0.75 C FOR THE SON SEASON. THE SST CONSOLIDATION PREDICTS ANOMALIES BETWEEN -1.0 AND -1.5 C THROUGH 2010 INTO EARLY 2011, THUS CLEARLY FAVORING LA NINA CONDITIONS. PROBABILITY OF LA NINA BY THE HALF DEGREE DEFINITION IS 87% BY NDJ ACCORDING TO THE CONSOLIDATION. 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 USED STRONGLY TO MODIFY THE CONSOLIDATION BEGINNING WITH THE SON 2010 SEASONAL OUTLOOK AND WINDING DOWN BY 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 FMA 2011. OUTLOOKS FOR MJJ 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 - SON 2010 TO SON 2011 TEMPERATURE ABOVE NORMAL TEMPERATURES ARE FAVORED IN SON 2010 FOR MOST OF THE LOWER 48 STATES EXCLUDING THE PACIFIC COAST, THE NORTHWEST AND SOUTHEAST. PROBABILITIES ARE PARTICULARLY ENHANCED FOR THE DESERT SOUTHWEST, AND THE GREAT LAKES AND NORTHEAST, DUE PRIMARILY TO DECADAL TEMPERATURE TRENDS AND LA NINA CONDITIONS. FOR OND 2010, ABOVE NORMAL TEMPERATURES ARE FAVORED FOR A REGION STRETCHING FROM THE SOUTHERN U.S. TO THE NORTHEAST, ASSOCIATED WITH BOTH EXPECTED LA NINA CONDITIONS AND TEMPERATURE TRENDS. 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 INTO THE NORTHERN PLAINS - FOR THE LATER LEADS THIS IS SUPPORTED BY TRENDS AS WELL. THE PROBABILITIES OF ABOVE NORMAL TEMPERATURES ARE ENHANCED IN MUCH OF THE SOUTHERN U.S. BY THE PROSPECT OF LA NINA CONDITIONS. THE OUTLOOKS FOR AMJ THROUGH SON 2011 PRIMARILY REFLECT DECADAL VARIABILITY IN THE LONG TERM CLIMATE STATE FAVORING ABOVE NORMAL TEMPERATURES FOR MUCH OF THE WEST, AND FOR SOME AREAS IN THE NORTHEAST. 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 SON 2010 INDICATES INCREASED CHANCES FOR ABOVE MEDIAN PRECIPITATION FOR AREAS IN THE NORTHWEST AND IN THE CENTRAL PLAINS THE FORMER DUE TO LA NINA, THE LATTER DUE TO LONG TERM TRENDS. LA NINA, WHEN CONSIDERED IN ISOLATION, FAVORS BELOW MEDIAN RAINFALL IN MUCH OF THE SOUTH BUT THIS IS CONTRADICTED IN SOME AREAS BY OTHER TOOLS, FOR EXAMPLE ALONG THE GULF COAST IN AN ACTIVE HURRICANE SEASON. BOTH TRENDS AND LA NINA COMPOSITES AGREE ON INCREASED CHANCES FOR BELOW MEDIAN PRECIPITATION IN THE SOUTHWEST AND THE CENTRAL MISSISSIPPI VALLEY. THE OUTLOOKS FOR OND 2010 THROUGH MAM 2011 SHOW THE EXPECTED IMPACT OF LA NINA CONDITIONS ON PRECIPITATION. LA NINA CONDITIONS ENHANCE THE PROBABILITIES OF ABOVE MEDIAN PRECIPITATION IN THE PACIFIC NORTHWEST AND NORTHERN ROCKIES IN THE FALL AND WINTER SEASONS AND IN THE CENTRAL INTERIOR REGIONS OF THE EASTERN U.S. IN WINTER. PROBABILITIES OF BELOW MEDIAN PRECIPITATION AMOUNTS ARE ENHANCED ACROSS MOST OF THE SOUTHERN U.S. IN THE WINTER BY THE INCREASING LIKELIHOOD OF LA NINA CONDITIONS, ESPECIALLY IN THE SOUTHEAST. 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 FROM AMJ THROUGH 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 THE LATER LEADS. NOTE - AREAS OF UNCERTAINTY THAT FORMERLY WERE LABELED CL (CLIMATOLOGICAL PROBABILITIES) ARE NOW LABELED EC (EQUAL CHANCES). FORECASTER: HUUG VAN DEN DOOL 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 SEP 16 2010 1971-2000 BASE PERIOD MEANS WERE IMPLEMENTED EFFECTIVE WITH THE MAY 17, 2001 FORECAST RELEASE. $$