PROGNOSTIC DISCUSSION FOR LONG-LEAD SEASONAL OUTLOOKS NWS CLIMATE PREDICTION CENTER CAMP SPRINGS MD 830 AM EDT THU JUN 17 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 ARE UNDERGOING A RAPID TRANSITION FROM ABOVE NORMAL IN APRIL, TO BELOW NORMAL IN THE EARLY PART OF JUNE. THIS INDICATES A TRANSITION IN THE ENSO STATE FROM EL NINO IN SPRING TO NEUTRAL CONDITIONS IN EARLY JUNE. THE MOST RECENT 7-DAY MEAN SEA SURFACE TEMPERATURES ARE BELOW NORMAL ALONG THE EQUATOR FROM ABOUT 170W TO THE SOUTH AMERICAN COAST, WITH SSTS PREDOMINATELY MORE THAN 1 DEGREE C BELOW NORMAL FROM ABOUT 150W TO 90W. THIS SUGGESTS THE POSSIBILITY OF DEVELOPING LA NINA CONDITIONS BY LATE SUMMER. ATMOSPHERIC CONDITIONS OVER THE TROPICAL PACIFIC ARE ALSO SHOWING SOME SIGNS OF A TRANSITION TO LA NINA CONDITIONS, CHARACTERIZED BY ABOVE NORMAL EASTERLY TRADE WINDS, SUPRESSED CONVECTION OVER THE EAST CENTRAL PACIFIC, AND ENHANCED CONVECTION OVER INDONESIA. LA NINA-LIKE CONDITIONS HAVE ONLY RECENTLY APPEARED AND THE CURRENT ENSO STATE IS BEST CLASSIFIED AS NEUTRAL. AN OFFICIAL CLASSIFICATION OF LA NINA REQUIRES AT LEAST THREE CONSECUTIVE MONTH OF LA NINA CONDITIONS. THERE IS CURRENTLY A DEEP LAYER OF BELOW NORMAL OCEAN TEMPERATURES EXTENDING FROM THE SURFACE TO 250 METERS DEPTH THROUGHOUT THE EASTERN PACIFIC, MAKING IT UNLIKELY FOR SST ANOMALIES TO RETURN TO POSITIVE VALUES THIS SUMMER. THE MAJORITY OF STATISTICAL AND DYNAMICAL MODELS PREDICT NEGATIVE SST ANOMALIES THROUGH THE END OF THE YEAR, SUGGESTING THE POSSIBLE DEVELOPMENT OF LA NINA CONDITIONS BY AS EARLY AS LATE SUMMER AND CONTINUING THROUGH THE END OF THE YEAR. PROBABILISTIC PREDICTIONS FROM THE CONSOLIDATION FORECAST INDICATE A NEARLY 70% CHANCE OF THE DEVELOPMENT OF LA NINA BY WINTER. SOME CONSIDERATION OF LA NINA RELATED CLIMATE IMPACTS WERE CONSIDERED FOR OUTLOOKS FROM JAS 2010 THROUGH TO THE SPRING OF 2011, WITH THE LARGEST POTENTIAL IMPACTS OCCURRING IN WINTER. THE JAS 2010 TEMPERATURE OUTLOOK FAVORS ABOVE-NORMAL SEASONAL MEAN TEMPERATURES FOR PARTS OF THE GREAT BASIN AND THE DESERT SOUTHWEST, EXTENDING EASTWARD INTO TEXAS AND THE SOUTHEASTERN STATES, AND THEN NORTHWARD ALONG THE EASTERN SEABOARD TO NEW ENGLAND. ABOVE NORMAL TEMPERATURES ARE ALSO FAVORED FOR INTERIOR ALASKA. THESE PRIMARILY REFLECT REGIONS OF RELIABLE WARMING TRENDS IN TEMPERATURES. BELOW NORMAL SSTS IN THE BERING SEA ARE EXPECTED TO ENHANCED CHANCES FOR BELOW-NORMAL TEMPERATURES IN COASTAL REGIONS OF SOUTHWESTERN ALASKA AND THE ALEUTIANS. BELOW NORMAL TEMPERATURES ARE ALSO FAVORED FOR PARTS OF THE CENTRAL GREAT PLAINS DUE TO WET INITIAL SOIL MOISTURE CONDITIONS, AND INDICATIONS FROM THE CFS. LA NINA CONDITIONS FAVOR ABOVE MEDIAN PRECIPITATION AMOUNTS IN PARTS OF THE SOUTHEASTERN STATES, WHICH IS ALSO CONSISTENT WITH THE NOAA FORECAST FOR AN ACTIVE ATLANTIC HURRICANE SEASON AND LONG TERM TRENDS IN THE REGION. THE AREA OF ENHANCED CHANCES OF ABOVE MEDIAN PRECIPITATION AMOUNTS MAY REFLECT ADDITIONAL MOISTURE FROM FRONTAL SYSTEMS AS WELL AS TROPICAL STORMS, SO THIS OUTLOOK SHOULD NOT BE USED TO IMPLY CHANGES IN TROPICAL STORM STRIKE PROBABILITIES. THE CHANCES OF ABOVE MEDIAN PRECIPITATION AMOUNTS ARE ALSO ENHANCED OVER PARTS OF THE CENTRAL GREAT PLAINS, MAINLY DUE TO LONG TERM TRENDS AND ABOVE AVERAGE SOIL MOISTURE EARLY IN THE SUMMER SEASON. 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. 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 PREDOMINATELY NEGATIVE FROM ABOUT 170W TO THE SOUTH AMERICAN COAST. THE MOST RECENT 7-DAY MEAN SEA SURFACE TEMPERATURES ANOMALIES ARE -1.0 DEGREE C OR COLDER ALONG THE EQUATOR FROM ABOUT 150W TO 90W. TROPICAL LOW LEVEL EASTERLY WINDS OVER THE PACIFIC ARE STRONGER THAN AVERAGE EAST OF THE DATE LINE. A RESERVOIR OF ABNORMALLY COOL WATER HAS DEVELOPED FROM THE SURFACE TO AROUND 250 METERS DEPTH ACROSS THE EASTERN EQUATORIAL PACIFIC, WITH ANOMALIES BETWEEN 50 AND 100 METERS DEPTH OF -3 TO -5 DEGREES C. TROPICAL CONVECTION IS NOW SUPRESSED OVER THE CENTRAL PACIFIC OCEAN AND ENHANCED NEAR INDONESIA. THESE OBSERVATIONS ARE SUGGESTIVE OF LA NINA CONDITIONS, HOWEVER IN VIEW OF THE FACT THAT THESE CONDITIONS HAVE ONLY RECENTLY DEVELOPED, THE CURRENT ENSO STATE IS BEST CLASSIFIED AS ENSO NEUTRAL. PROGNOSTIC DISCUSSION OF SST FORECASTS BIAS-CORRECTED FORECASTS FROM THE NCEP CLIMATE FORECAST SYSTEM (CFS), A DYNAMICAL COUPLED OCEAN-ATMOSPHERE MODEL, INDICATE THAT THE NINO 3.4 SST ANOMALY WILL CONTINUE TO FALL, WITH THE PREDICTED SEASONAL MEAN SST FOR JAS EXPECTED TO BE AROUND -1.0 C. THE CPC SST CONSOLIDATION FORECAST (AN OBJECTIVE, SKILL WEIGHTED COMBINATION OF THE CFS AND THREE STATISTICAL SST FORECASTS) PREDICTS THAT ANOMALIES WILL HOVER AROUND -.4 C THIS SUMMER. THE CFS MODEL STRENGTHENS THE NEGATIVE ANOMALIES LATE IN THE YEAR, WITH BIAS CORRECTED ANOMALIES APPROACHING -1.5 C BY THE END OF 2010. THE CONSOLIDATION FORECAST PREDICTS ANOMALIES BETWEEN -.5 C AND -1.0 C BY LATE FALL, AND THESE ANOMALIES ARE CLEARLY STRONG ENOUGH TO SUPPORT LA NINA CONDITIONS THIS WINTER. PROBABILISTIC PREDICTIONS BY THE CONSOLIDATION FORECAST SUGGESTS A 50% CHANCE OF LA NINA DEVELOPMENT BY FALL, AND NEARLY 70% BY THE END OF THE YEAR. 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 TEMPERATURE AND PRECIPITATION OUTLOOKS. LA NINA COMPOSITES WERE ALSO USED, STARTING IN JAS 2010 AND CONTINUING THROUGH AMJ 2011. THE CFS TEMPERATURE AND PRECIPITATION FORECASTS WERE USED UP TO AND INCLUDING DJF 2010-11. OUTLOOKS FOR MJJ 2011 AND BEYOND ARE BASED PRIMARILY ON CPC CONSOLIDATION FORECAST WHICH IS DOMINATED BY TREND AT THOSE LEAD TIMES. PROGNOSTIC DISCUSSION OF OUTLOOKS - JAS 2010 TO JAS 2011 TEMPERATURE: ABOVE NORMAL TEMPERATURES ARE FAVORED IN JAS 2010 FOR INTERIOR ALASKA, CENTRAL AND SOUTHERN SECTIONS OF THE INTERIOR WEST, THE GULF COAST, THE SOUTHEAST, AND ALONG MUCH OF THE EASTERN SEABOARD, DUE PRIMARILY TO DECADAL TRENDS. THE CHANCES OF BELOW NORMAL TEMPERATURES ARE ELEVATED OVER THEIR CLIMATOLOGICAL PROBABILITY IN PARTS OF THE CENTRAL GREAT PLAINS. THIS FORECAST HAS SUPPORT FROM CFS AND ALSO IS CONSISTENT WITH THE COOLING INFLUENCE OF WET SOIL MOISTURE CONDITIONS IN THE REGION IN JUNE. BELOW NORMAL SSTS IN THE BERING SEA ENHANCE THE CHANCES OF BELOW NORMAL TEMPERATURES ALONG THE SOUTHWESTERN ALASKAN COAST AND THE ALEUTIANS. FOR ASO - OND 2010 ABOVE NORMAL TEMPERATURES ARE FAVORED FOR PARTS OF THE SOUTHERN CONUS, THE NORTHEASTERN CONUS, AND NORTHERN ALASKA DUE PRIMARILY TO LONG TERM TEMPERATURES TRENDS. THE OUTLOOKS FOR NDJ 2010-11 THROUGH AMJ 2011 REFLECT EXPECTED LA NINA IMPACTS. THE CHANCES OF BELOW NORMAL TEMPERATURES ARE ENHANCED IN MOST OF ALASKA, THE PACIFIC NORTHWEST, THE NORTHERN ROCKIES, AND INTO THE NORTHERN GREAT PLAINS. THIS FORECAST IS CONSISTENT WITH EXPECTED ANOMALIES DURING LA NINA WINTERS. LA NINA WINTERS TEND TO ELEVATE CHANCES OF ABOVE NORMAL TEMPERATURES IN MUCH OF THE SOUTHERN CONUS. OCN TEMPERATURE FORECASTS INDICATE THAT TRENDS FAVORING WARMER THAN NORMAL CONDITIONS IN WINTER OVER THE CONUS HAVE NOT BEEN AS STRONG IN RECENT YEARS AS EARLIER IN THE DECADE EXCEPT IN THE SOUTHWEST, SO THE TEMPERATURE FORECASTS REFLECT LA NINA COMPOSITES WITH ONLY MINOR ADJUSTMENTS DUE TO TEMPERATURE TRENDS. FROM MJJ THROUGH JAS 2011, THE OUTLOOK PRIMARILY REFLECTS TEMPERATURE TRENDS WHICH FAVOR ABOVE-NORMAL TEMPERATURES ACROSS THE PARTS OF THE WESTERN CONUS, AND NEAR THE COASTS IN THE EAST. ABOVE NORMAL TEMPERATURES ARE ALSO FAVORED IN PARTS OF ALASKA. ELEVATED CHANCES OF BELOW-NORMAL TEMPERATURES IN THE NORTHERN PLAINS IN MJJ 2011 PRIMARILY REFLECT TRENDS. PRECIPITATION: THE PRECIPITATION OUTLOOK FOR JAS 2010 INDICATES INCREASED CHANCES FOR ABOVE-MEDIAN PRECIPITATION FOR PORTIONS OF THE CENTRAL GREAT PLAINS DUE TO BOTH LONG TERM TRENDS AND INITIALLY WET SOIL MOISTURE CONDITIONS THAT CAN PROVIDE A LOCAL MOISTURE SOURCE FOR FRONTAL SYSTEMS. ABOVE MEDIAN PRECIPITATION IS FAVORED ALONG THE GULF COAST, FLORIDA, AND THE SOUTHEASTERN ATLANTIC COASTS. THE FORECAST FOR THE PACIFIC NORTHWEST AND NORTHERN ROCKY MOUNTAINS WAS SUBSTANTIALLY REVISED FROM THE PREVIOUS OUTLOOK FOR JAS AND NOW REFLECTS EQUAL CHANCES FOR ABOVE-NEAR-OR BELOW MEDIAN PRECIPITATION RATHER THAN FAVORING DRY CONDITIONS AS INDICATED IN LAST MONTHS OUTLOOK. THIS REVISION REFLECTS THE CFS FORECAST OF ABOVE MEDIAN PRECIPITATION IN CONTRADICTION TO RECENT LONG TERM TRENDS. THERE ARE CONFLICTING SIGNALS REGARDING THE STRENGTH OF THE SOUTHWEST MONSOON. BOTH THE CFS AND IRI MULTI-MODEL ENSEMBLE FAVOR BELOW MEDIAN PRECIPITATION, WHILE LA NINA COMPOSITES FAVOR A STRONGER THAN AVERAGE MONSOON, SO AN EQUAL CHANCES FORECAST SEEMS MOST APPROPRIATE AT THIS TIME. THE OUTLOOK FOR ASO 2010 PRIMARILY REFLECTS PRECIPITATION TRENDS IN THE WESTERN HALF OF THE COUNTRY, AND A COMBINATION OF TRENDS AND LA NINA COMPOSITES IN THE EAST. TRENDS FAVORING ABOVE MEDIAN PRECIPITATION IN PARTS OF THE NORTHERN GREAT PLAINS EXTEND INTO SON 2010. THE OUTLOOKS FOR SON 2010 THROUGH MAM 2011 SHOW THE EXPECTED IMPACT OF LA NINA ON PRECIPITATION. LA NINA ENHANCES CHANCES OF ABOVE MEDIAN PRECIPITATION IN THE PACIFIC NORTHWEST AND NORTHERN ROCKIES IN FALL AND WINTER, AND ALSO IN PARTS OF THE EAST-CENTRAL CONUS IN THE WINTER. BELOW MEDIAN PRECIPITATION AMOUNTS ARE FAVORED THROUGHOUT MUCH OF THE SOUTHERN THIRD OF THE CONUS IN LA NINA WINTERS, ESPECIALLY IN THE SOUTHEAST WHERE THE LA NINA SIGNAL IS STRONG AND TRENDS ALSO FAVOR BELOW MEDIAN PRECIPITATION. THE LA NINA SIGNAL GRADUALLY FADES IN THE SPRING, AS DOES THE CONFIDENCE IN THE CONTINUATION OF LA NINA CONDITIONS, LEAVING LITTLE IN THE WAY OF SIGNAL FOR PRECIPITATION ANOMALIES FROM AMJ THROUGH JJA 2011. TRENDS TOWARD BELOW MEDIAN PRECIPITATION IN THE PACIFIC NORTHWEST AND TOWARDS ABOVE MEDIAN PRECIPITATION IN FLORIDA INFLUENCE THE PRECIPITATION AMOUNT PROBABILITIES IN THOSE REGIONS IN JAS 2011. 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 JUL 15 2010 1971-2000 BASE PERIOD MEANS WERE IMPLEMENTED EFFECTIVE WITH THE MAY 17, 2001 FORECAST RELEASE. $$