PROGNOSTIC DISCUSSION FOR LONG-LEAD SEASONAL OUTLOOKS NWS CLIMATE PREDICTION CENTER CAMP SPRINGS MD 830AM EDT THURSDAY APR 21 2011 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 SPRING AND 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). AN UPGRADED PARALLEL VERSION OF THE CFS (CFSV2) BECAME OPERATIONAL IN MARCH 2011. IT IS ANTICIPATED THAT BOTH CFS VERSIONS WILL BE RUN IN PARALLEL UNTIL AT LEAST JUNE 2011. 9) CONSOLIDATION (CON) - AN OBJECTIVE, SKILL WEIGHTED COMBINATION 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. 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 NEAR 140W, WITH SSTS BETWEEN 0 AND 1.5 DEGREES C BELOW NORMAL IN SOME AREAS. ABNORMALLY COOL SSTS IMPACT THE LARGE SCALE ATMOSPHERIC CIRCULATION THROUGHOUT THE TROPICAL PACIFIC REGION, AND IN TURN, THE MEAN ATMOSPHERIC CIRCULATION PATTERNS OVER NORTH AMERICA. FORECASTS FROM MOST SST PREDICTION MODELS INDICATE LA NINA CONDITIONS WILL DIMINISH TO NEAR-NEUTRAL BY JUNE 2011. UNCERTAINTY IN THE ENSO STATE BEYOND SPRING 2011 IS HIGH. THE TEMPERATURE OUTLOOK FOR MJJ 2011 IS, OVERALL, CONSISTENT WITH LA NINA CONDITIONS. PROBABILITIES OF BELOW NORMAL TEMPERATURES ARE ENHANCED FROM THE PACIFIC NORTHWEST EASTWARD ACROSS THE NORTHERN ROCKIES THROUGH THE GREAT LAKES REGION, INTO THE MIDDLE ATLANTIC COAST REGION. THE OCN PREDICTS PROBABILITIES FOR ABOVE NORMAL TEMPERATURES ACROSS THE INTERIOR SOUTHWEST. THE SEASONAL PRECIPITATION OUTLOOK FOR MJJ 2011 CALLS FOR GENERALLY ABOVE-MEDIAN PRECIPITATION IN NORTHERN SECTIONS OF THE CONUS. BELOW MEDIAN PRECIPITATION IS LIKELY ACROSS THE SOUTH-CENTRAL U.S. AND IN PARTICULAR, TEXAS AND LOUISIANA. IN SPITE OF THE EXPECTED WEAKENING OF LA NINA TO NEUTRAL STATUS BY JUNE 2011, THE ABNORMALLY WET SOILS IN NORTHERN SECTIONS OF THE CONTIGUOUS UNITED STATES, AND ABNORMALLY DRY SOILS IN THE SOUTH, ARE LIKELY TO LEAD TO A CONTINUATION OF COOL, WET CONDITIONS IN THE NORTH AND WARM DRY CONDITIONS IN THE SOUTH. IN LOCATIONS WHERE THE LIKELIHOODS OF SEASONAL MEAN TEMPERATURES AND SEASONAL PRECIPITATION AMOUNTS ARE SIMILAR TO THE CLIMATOLOGICAL PROBABILITIES, EQUAL CHANCES (EC) 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 WHILE A LARGE AREA OF THE TROPICAL SSTS REMAIN BELOW NORMAL, NEGATIVE SST ANOMALIES HAVE DECREASED IN AMPLITUDE FROM THE CENTRAL PACIFIC TO THE SOUTH AMERICAN COAST DURING THE LAST 2 MONTHS AND ARE NOW SLIGHTLY ABOVE NORMAL IN THE EASTERN PACIFIC. THE SUBSURFACE OCEAN HEAT CONTENT MEASURED BY THE WATER TEMPERATURE IS BELOW NORMAL TO A DEPTH OF 50 TO 100 METERS FROM APPROXIMATELY THE DATELINE TO 140W. OCEAN HEAT CONTENT IS ABOVE NORMAL FROM THE SURFACE TO A DEPTH OF ABOUT 125 METERS EAST OF ABOUT 115W. ABOVE NORMAL OCEAN HEAT CONTENT IN THE WEST PACIFIC HAS CONTINUED TO EXPAND EASTWARD WITH POSITIVE TEMPERATURE ANOMALIES RISING TOWARDS THE SURFACE EAST OF 140W. TOTAL EQUATORIAL OCEANIC HEAT CONTENT BETWEEN 180 AND 100 W IS NOW POSITIVE, ON AVERAGE. AS OF MID-APRIL, THE LARGE SCALE ATMOSPHERIC CIRCULATION OVER THE TROPICAL PACIFIC OCEAN IS CONSISTENT WITH LA NINA CONDITIONS. CONVECTION IS SLIGHTLY ENHANCED OVER PARTS OF THE MARITIME CONTINENT NEAR THE EQUATOR. GREATER ENHANCED CONVECTION IS OBSERVED BOTH TO THE NORTH OF THE EQUATOR, AND TO THE SOUTH OVER NORTHERN AUSTRALIA, WHILE CONVECTION IS SUPPRESSED OVER THE WESTERN AND CENTRAL EQUATORIAL PACIFIC OCEAN, EAST OF ABOUT 150E. LOW LEVEL EASTERLY TRADE WINDS ARE ENHANCED OVER THE WESTERN AND CENTRAL PACIFIC. WESTERLY WIND ANOMALIES AT UPPER LEVELS ARE ENHANCED OVER THE CENTRAL AND EAST-CENTRAL PACIFIC WITH ANOMALOUS OFF-EQUATORIAL CYCLONIC CIRCULATIONS IN THE SUBTROPICS OF BOTH HEMISPHERES. OVERALL, THESE ATMOSPHERIC AND OCEANIC CONDITIONS ARE CONSISTENT WITH A WEAKENING LA NINA. THIS SET OF OUTLOOKS IS THE LAST ONE TO USE THE 1971-2000 CLIMATOLOGICAL NORMALS. DECADAL TRENDS, CURRENTLY ASSESSED RELATIVE TO THE 1971-2000, WILL, AFTER THE FORECAST FOR MJJ 2011-MJJ 2012, BE EVALUATED RELATIVE TO THE 1981-2010 NORMALS. PROGNOSTIC DISCUSSION OF SST FORECASTS STATISTICAL AND DYNAMICAL MODELS PREDICT NEGATIVE SST ANOMALIES IN THE EQUATORIAL PACIFIC TO DIMINISH DURING THE SPRING OF 2011 SUCH THAT ENSO NEUTRAL CONDITIONS ARE EXPECTED BY JUNE 2011. THE CPC CONSOLIDATION OF THE CFS, CONSTRUCTED ANALOG, MARKOV MODEL AND CCA NINO 3.4 FORECASTS INDICATES AN ANOMALY COOLER THAN -0.5 C ONLY THROUGH MAM2011, AND THE LIKELY POSSIBILITY OF A TRANSITION FROM LA NINA TO ENSO NEUTRAL CONDITIONS BY JUNE. THE CPC SST CONSOLIDATION FORECAST INDICATES THAT NINO 3.4 SST ANOMALIES ARE MOST LIKELY TO BE IN THE ENSO NEUTRAL RANGE (ANOMALIES OF FROM -0.5 TO +0.5 C) IN THE SUMMER. THERE A NUMBER OF MODEL FORECASTS PREDICTING LA NINA, ENSO NEUTRAL OR EL NINO CONDITIONS AFTER THAT TIME, AND UNCERTAINTY IS HIGH REGARDING THE ENSO STATE IN AUTUMN AND NEXT WINTER. PROGNOSTIC TOOLS USED FOR U.S. TEMPERATURE AND PRECIPITATION OUTLOOKS THE OUTLOOKS FOR MJJ 2011 WERE PRIMARILY BASED ON THE SKILL-WEIGHTED CONSOLIDATION (CON) FORECASTS, AND THE CFS DYNAMICAL MODELS. ONE IMPACT OF THE CURRENT LA NINA WAS ABNORMALLY LOW PRECIPITATION IN THE SOUTH, AND UNUSUALLY ABUNDANT PRECIPITATION IN NORTHERN SECTIONS OF THE CONUS DURING MUCH OF THE COLD SEASON. THE RESULTANT SOIL MOISTURE CONDITIONS INCREASE THE LIKELIHOOD OF ABOVE NORMAL TEMPERATURES IN THE SOUTHERN U.S., AND BELOW NORMAL TEMPERATURES IN THE CENTRAL MISSISSIPPI AND OHIO VALLEYS. BOTH DYNAMICAL AND STATISTICAL MODELS WERE CONSIDERED FOR THE FORECAST THROUGH THE WARM SEASON. BEYOND SON, THE FORECAST IS BASED ENTIRELY ON STATISTICAL MODELS, INCLUDING TREND (OCN), CCA, SMLR, AND ECCA, AND THE CONSOLIDATION FORECAST (CON) BASED ON WEIGHTINGS OF THOSE TOOLS. PROGNOSTIC DISCUSSION OF OUTLOOKS - MJJ 2011 TO MJJ 2012 TEMPERATURE ALTHOUGH IT WAS BASED MAINLY ON DYNAMICAL AND STATISTICAL MODELS, AND CONSOLIDATION FORECASTS, THE 3-MONTH TEMPERATURE OUTLOOK FOR MJJ 2010 IS CONSISTENT WITH TYPICAL LA NINA IMPACTS. FOR MJJ 2011, THERE IS AN ELEVATED CHANCE OF BELOW NORMAL TEMPERATURES FROM THE NORTHWEST, ACROSS THE NORTHERN GREAT PLAINS, THE GREAT LAKES, AND THE MIDDLE ATLANTIC COAST REGION. AT EARLY LEADS, AN INCREASED CHANCE OF ABOVE NORMAL TEMPERATURES IS INDICATED FOR MUCH OF THE INTERIOR SOUTHWEST. IN THE LATER LEADS, THE LONGER-TERM TRENDS INCREASE THE LIKELIHOOD OF ABOVE NORMAL TEMPERATURES FOR THE NORTHEAST AND THE GREAT LAKES REGION. ABOVE NORMAL TEMPERATURES ARE ALSO SLIGHTLY FAVORED IN THE LATER LEADS FOR ALASKA, WHERE WARMING TRENDS HAVE BEEN RELIABLE INDICATORS OF SEASONAL MEAN TEMPERATURES. PRECIPITATION THE PRECIPITATION OUTLOOK FOR MJJ 2011 CALLS FOR GENERALLY ABOVE-MEDIAN PRECIPITATION IN NORTHERN SECTIONS OF THE CONUS, AND BELOW-MEDIAN PRECIPITATION IN THE SOUTH. BELOW MEDIAN PRECIPITATION IS LIKELY ACROSS MUCH OF THE SOUTHERN U.S. AND IN PARTICULAR, THE SOUTHWEST. IN SPITE OF THE FORECASTED WEAKENING OF LA NINA IN THE SPRING, SOIL MOISTURE ANOMALIES IN REGIONS WITH A WINTER PRECIPITATION DEFICIT MAY DECREASE LOCAL MOISTURE SOURCES THROUGH EVAPORATION AND INCREASE THE CHANCES FOR THE CONTINUATION OF BELOW MEDIAN PRECIPITATION INTO SPRING. DECADAL TRENDS LEAD TO ENHANCED CHANCES OF BELOW MEDIAN PRECIPITATION IN THE PACIFIC NORTHWEST AND OF ABOVE MEDIAN PRECIPITATION IN NEW ENGLAND IN JAS AND ASO. TRENDS ALSO INDICATE A GREATER LIKELIHOOD OF ABOVE MEDIAN PRECIPITATION IN SOUTHERN FLORIDA AND THE CENTRAL PLAINS DURING LATE SUMMER AND EARLY AUTUMN. MOST OF THE OUTLOOKS BEYOND SON 2011 SHOW EQUAL CHANCES (EC) BECAUSE OF A LACK OF CLIMATE SIGNALS, EXCEPT FOR ENHANCED CHANCES OF BELOW MEDIAN PRECIPITATION IN THE SOUTHEAST DUE TO LONG TERM TRENDS IN JFM AND FMA 2012. 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 MAY 19 2011 1971-2000 BASE PERIOD MEANS WERE IMPLEMENTED EFFECTIVE WITH THE MAY 17, 2001 FORECAST RELEASE. $$