PROGNOSTIC DISCUSSION FOR LONG-LEAD SEASONAL OUTLOOKS NWS CLIMATE PREDICTION CENTER CAMP SPRINGS MD 830 AM EDT THU MAY 20 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. EL NINO CONDITIONS RAPIDLY SUBSIDED ACROSS THE TROPICAL PACIFIC DURING APRIL AND EARLY MAY. THE MOST RECENT 7-DAY MEAN SEA SURFACE TEMPERATURE DEPARTURES FROM NORMAL RANGE FROM 0.5 TO 1.0 C BELOW NORMAL IN THE EQUATORIAL EASTERN PACIFIC BETWEEN 120W AND 150W. THERE IS A SMALL REGION OF +0.5 TO +1.0 C ANOMALIES BETWEEN ABOUT 90W AND THE COAST OF SOUTH AMERICA. TROPICAL LOW LEVEL EASTERLY WINDS ARE STRONGER THAN AVERAGE WEST OF THE DATE LINE TO 120E. A RESERVOIR OF ABNORMALLY COLD WATER HAS DEVELOPED BETWEEN 200 METERS AND 100 METERS BELOW THE SURFACE BETWEEN 150E ACROSS THE DATE LINE TO 110W. THESE CONDITIONS RAISE THE LIKELIHOOD OF A LA NINA EVENT TO ROUGHLY 50% FOR LA NINA, 50% FOR NEUTRAL, AND NEGLIGIBLE FOR EL NINO. THIS FORECAST FACTORS-IN A MODEST TILT TOWARD LA NINA IMPACTS FROM SUMMER 2010 THROUGH SPRING 2011, WITH THE LARGEST POTENTIAL LA NINA IMPACTS OCCURRING IN LATE WINTER. THE JJA 2010 TEMPERATURE OUTLOOK INDICATES THAT ABOVE-NORMAL SEASONAL MEAN TEMPERATURES ARE FAVORED FOR CENTRAL AND SOUTHERN SECTIONS OF THE WEST, FOR INTERIOR ALASKA, AND FOR THE SOUTHEAST. ENHANCED CHANCES FOR BELOW-NORMAL TEMPERATURES ARE GIVEN FOR PORTIONS OF TEXAS THROUGH THE GREAT PLAINS AND GREAT LAKES, AND FOR THE ALEUTIANS. THE CHANCES OF ABOVE MEDIAN SEASONAL PRECIPITATION DURING JJA 2010 ARE GREATER THAN CLIMATOLOGY FOR SECTIONS OF THE CENTRAL AND NORTHERN GREAT PLAINS AND THE GULF COAST AND FLORIDA. PRECIPITATION IS LIKELY TO BE BELOW HISTORICAL MEDIAN VALUES IN THE NORTHWEST. IN LOCATIONS WHERE THE LIKELIHOOD SEASONAL MEAN TEMPERATURE AND SEASONAL TOTAL PRECIPITATION IS SIMILAR TO THE CLIMATOLOGICAL PROBABILITIES, EQUAL CHANCES OF BELOW, NEAR, AND ABOVE-AVERAGE TEMPERATURE AND PRECIPITATION ARE INDICATED. NOTE THAT THE OUTLOOKS FOR NDJ 2010-2011 THROUGH AMJ 2011 ARE SUBSTANTIALLY REVISED FROM LAST MONTH'S OUTLOOKS DUE TO INDICATIONS OF THE DEVELOPMENT OF LA NINA CONDITIONS. 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 SEA SURFACE TEMPERATURE (SST) ANOMALIES DECLINED DRAMATICALLY ACROSS MANY AREAS OF THE EQUATORIAL PACIFIC OCEAN. THE MOST RECENT 7-DAY MEAN SEA SURFACE TEMPERATURE DEPARTURES FROM NORMAL RANGE FROM 0.5 TO 1.0 C BELOW NORMAL IN THE EQUATORIAL EASTERN PACIFIC BETWEEN 120W AND 150W. THERE IS A SMALL REGION OF +0.5 TO +1.0 C ANOMALIES BETWEEN ABOUT 90W AND THE COAST OF SOUTH AMERICA. TROPICAL LOW LEVEL EASTERLY WINDS ARE STRONGER THAN AVERAGE WEST OF THE DATE LINE TO 120E. A RESERVOIR OF ABNORMALLY COLD WATER HAS DEVELOPED BETWEEN 200 METERS AND 100 METERS BELOW THE SURFACE BETWEEN 150E ACROSS THE DATE LINE TO 110W. THESE DEVELOPMENTS, AND MODEL FORECASTS HAVE INCREASED THE CHANCES OF A LA NINA EVENT THROUGH SPRING OF 2011. HOWEVER, THERE ARE INHERENT UNCERTAINTIES IN SUCH A PREDICTION, AND THE CURRENT PROBABILITIES FOR ENSO PHASE ARE ESTIMATED (BASED ON A SUBJECTIVE CONSENSUS AMONG PARTICIPANTS IN THE FORECAST FROM CPC, ESRL AND IRI) TO BE ABOUT 50% FOR COLD, 50% FOR NEUTRAL, AND 0% FOR ABOVE. THIS FORECAST INCORPORATES A MODEST TILT TOWARD LA NINA IMPACTS, WITH RELATIVELY LOW PROBABILITIES, THROUGH AMJ OF 2011. PROGNOSTIC DISCUSSION OF SST FORECASTS BIAS-CORRECTED FORECASTS FROM THE NCEP CLIMATE FORECAST SYSTEM (CFS) DYNAMICAL COUPLED OCEAN-ATMOSPHERE MODEL INDICATE THAT THE NINO 3.4 SST ANOMALY WILL FALL TO -0.5 C DURING MJJ 2010. THE CPC SST CONSOLIDATION FORECAST (AN OBJECTIVE, SKILL WEIGHTED COMBINATION OF THE CFS AND THREE STATISTICAL SST FORECASTS) PREDICTS 0.0 C ANOMALIES BY MJJ 2010. THAT FORECAST TOOL, AND MANY OF THE STATISTICAL TOOLS INDICATE LITTLE OR NO DROP IN SSTS BELOW NORMAL VALUES THROUGH SUMMER 2010. NOTABLE EXCEPTIONS TO THIS ARE THE CONSTRUCTED ANALOG (CA) AND THE LINEAR INVERSE MODEL (LIM), WHICH DO PREDICT A TRANSITION TO LA NINA BY MJJ 2010. CFS PREDICTS COLD CONDITIONS TO DEVELOP, REACHING THE NOMINAL -0.5 C CRITERION FOR LA NINA CONDITIONS JUST AFTER MJJ 2010. CFS PREDICTS NINO 3.4 SST ANOMALIES TO HOLD AT ABOUT -0.6 C THROUGH ASO 2010, AND THEN COOL TO BELOW -1.0 C JUST AFTER SON 2010. 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 MAJORITY OF THE SEASONAL OUTLOOKS. DURING THE FIRST TWO LEADS SOIL MOISTURE AND SST CONDITIONS WERE USED IN SOME AREAS TO MODIFY THE FORECAST. LA NINA COMPOSITES WERE ALSO USED, STARTING IN SUMMER 2010 AND CONTINUING THROUGH AMJ 2010. THE CFS TEMPERATURE AND PRECIPITATION FORECASTS WERE USED UP TO AND INCLUDING NDJ 2010. THE TEMPERATURE AND PRECIPITATION OUTLOOKS FROM NDJ 2010 THROUGH JJA 2011 ARE BASED ON LA NINA COMPOSITES, AND THE CPC CONSOLIDATION FORECAST WHICH IS DOMINATED BY TREND. NOTE THAT THE OUTLOOKS FOR NDJ 2010-2011 THROUGH AMJ 2011 ARE SUBSTANTIALLY REVISED FROM LAST MONTH'S OUTLOOKS DUE TO INDICATIONS OF THE DEVELOPMENT OF LA NINA CONDITIONS. PROGNOSTIC DISCUSSION OF OUTLOOKS - JJA 2010 TO JJA 2011 TEMPERATURE: THE TEMPERATURE OUTLOOK FOR JJA 2010 INDICATES THAT THE CHANCES OF BELOW NORMAL TEMPERATURES ARE ELEVATED OVER THEIR CLIMATOLOGICAL PROBABILITY FOR MUCH OF THE GREAT PLAINS AND GREAT LAKES REGIONS. ABOVE NORMAL TEMPERATURES ARE FAVORED FOR CENTRAL AND SOUTHERN SECTIONS OF THE INTERIOR WEST, INTERIOR ALASKA, THE GULF COAST, AND SECTIONS OF THE SOUTHEAST. ABOVE NORMAL SOIL MOISTURE, DYNAMICAL MODEL FORECASTS AND DECADAL TEMPERATURE TRENDS CONTRIBUTE TO THE FORECAST OF ENHANCED CHANCES FOR BELOW NORMAL TEMPERATURES FOR THE CENTRAL CONUS. FOR THE SOUTHERN PLAINS, A COMBINATION OF DYNAMICAL MODEL FORECASTS, AND ABOVE NORMAL SOIL MOISTURE ALSO ENHANCE CHANCES FOR BELOW-NORMAL TEMPERATURES. THE CONSOLIDATION INDICATES INCREASED CHANCES FOR ABOVE NORMAL TEMPERATURES IN THE SOUTHEAST, BUT MODEST PROBABILITIES ARE GIVEN DUE TO RELATIVELY COLD SEA SURFACE TEMPERATURES IN NEARBY COASTAL WATERS. FOR THE WESTERN CONUS, ABOVE-NORMAL TEMPERATURES ARE FAVORED WITH THE HIGHEST PROBABILITY IN THE INTERIOR SOUTHWEST WHERE TRENDS ARE LARGE IN THIS SEASON, LARGE ENOUGH TO OVERCOME SOMEWHAT COOL INDICATIONS FROM DYNAMICAL MODELS. NO SUBSTANTIAL CLIMATE SIGNALS ARE PRESENT FROM THE FORECAST TOOLS ACROSS THE REMAINDER OF THE U.S. SO CLIMATOLOGICAL PROBABILITIES FOR THE THREE CATEGORIES ARE INDICATED. JAS BEARS A CLOSE RESEMBLANCE TO JJA FOR THE SAME REASONS GIVEN FOR THAT SEASON. THE COOLING EFFECT OF SOIL MOISTURE IS LIKELY TO DECLINE TO NEAR-ZERO BY ASO, WHEN THE FORECAST CALLS FOR CONTINUED ENHANCED WARMTH IN THE WEST, DUE TO TREND, AND IN THE GREAT LAKES AND NORTHEAST AND FLORIDA, BASED ON GOOD OVERALL CONSENSUS AMONG TOOLS. IN SON AND OND, RELATIVE WARMTH CONTINUES IN THE SOUTHWEST AND SOUTH-CENTRAL CONUS, AND IN NEW ENGLAND. ONCE AGAIN, A GOOD CONSENSUS AMONG TOOLS IS BEHIND THIS FORECAST. THE EXCEPTION TO THIS IS THE CFS, WHICH FORECASTS COLDER THAN NORMAL TEMPERATURES THROUGHOUT THE NORTHERN CONUS DURING THIS PERIOD. THE CONSENSUS AMONG THE OTHER TOOLS OVERRODE THE CFS IN THE CON, WHICH WAS USED AS A GUIDE FOR THESE FORECASTS. FORECASTS FOR NDJ THROUGH AMJ INDICATE A MODEST TILT TOWARD LA NINA IMPACTS, INCLUDING SUB-NORMAL TEMPERATURES IN ALASKA AND IN SECTIONS OF THE NORTHERN AND NORTHWESTERN CONUS. ENHANCED LIKELIHOOD OF ABOVE NORMAL TEMPERATURES IS PREDICTED FOR THE SOUTH AND SOUTHWEST. THEREAFTER THROUGH JJA 2011, INCREASED CHANCES FOR ABOVE-NORMAL TEMPERATURES ARE INDICATED ACROSS THE SOUTHWEST U.S. AND PARTS OF ALASKA, WITH ELEVATED CHANCES OF BELOW-NORMAL TEMPERATURES IN THE NORTHERN PLAINS IN MJJ AND JJA 2011. THESE SIGNALS ARE PRIMARILY TRENDS. PRECIPITATION: THE PRECIPITATION OUTLOOK FOR JJA 2010 INDICATES INCREASED CHANCES FOR ABOVE-MEDIAN PRECIPITATION FROM OKLAHOMA THROUGH THE DAKOTAS, THE GULF COAST, AND FLORIDA (BASED ON THE CAS). THE PREDICTION OF ENHANCED LIKELIHOOD OF ABOVE MEDIAN PRECIPITATION IN THE CENTRAL PLAINS HAS SOME SUPPORT FROM CON, CFS, IRI, ECP, AND CAS. THE DRY SIGNAL IN THE NORTHWEST IS BASED ON CON, WHICH IS DOMINATED BY TREND THERE. FROM JAS 2010 THROUGH JJA 2011, THE CON WAS THE PRIMARY BASIS FOR THE FORECASTS WITH THE STRONGEST INFLUENCE FROM LONG-TERM TRENDS AND STATISTICAL FORECAST TOOLS. HOWEVER, THESE IMPACTS ARE AT LEAST PARTIALLY CONSISTENT WITH LA NINA, AT LEAST THROUGH MAM OR AMJ 2011, ESPECIALLY WETNESS ALONG THE GULF COAST AND FLORIDA IN THE 2010 WARM SEASON, TRANSITIONING TO SUB-MEDIAN PRECIPITATION IN THE LATE FALL AND WINTER 2010-2011 THERE. ENHANCED CHANCES FOR ABOVE-MEDIAN PRECIPITATION IN THE OHIO VALLEY AND SECTIONS OF THE NORTHWEST DURING WINTER 2010-2011 ARE ALSO CONSISTENT WITH LA NINA IMPACTS. NOTE - AREAS OF UNCERTAINTY THAT FORMERLY WERE LABELED CL (CLIMATOLOGICAL PROBABILITIES) ARE NOW LABELED EC (EQUAL CHANCES). FORECASTER: ED O'LENIC 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 JUN 17 2010 1971-2000 BASE PERIOD MEANS WERE IMPLEMENTED EFFECTIVE WITH THE MAY 17, 2001 FORECAST RELEASE. $$