PROGNOSTIC DISCUSSION FOR LONG-LEAD SEASONAL OUTLOOKS NWS CLIMATE PREDICTION CENTER COLLEGE PARK MD 830AM EDT THURSDAY SEP 20 2012 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 TOGETHER 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", WHICH ARE USED AT TIMES 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 1981-2010). 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 CONSIDERED LESS PREDICTABLE ON A SEASONAL TIMESCALE THAN ENSO. 5) THE PACIFIC DECADAL OSCILLATION (PDO) - AN ENSO-LIKE PATTERN OF CLIMATE VARIABILITY AFFECTING 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). THE UPGRADED PARALLEL VERSION OF THE CFS (CFSV2) BECAME OPERATIONAL IN LATE MARCH OF 2011. BOTH VERSIONS OF CFS ARE CURRENTLY RUN IN PARALLEL. AN EXPERIMENTAL MODEL FORECAST SYSTEM, THE NATIONAL MULTI-MODEL ENSEMBLE, COMPRISED OF SEVERAL MODELS AND DESIGNATED NMME, MAY ALSO BE USED EXPERIMENTALLY AND SUBJECTIVELY UNTIL IT IS INCLUDED INTO THE CONSOLIDATION. AN INTERNATIONAL MODEL ENSEMBLE DESIGNATED IMME IS ALSO AVAILABLE. 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. ENSO NEUTRAL CONDITIONS HAVE CONTINUED INTO SEPTEMBER. WE REMAIN CURRENTLY UNDER AN EL NINO WATCH. SEA SURFACE TEMPERATURES (SSTS) ARE NOW ABOVE NORMAL ALONG THE EQUATOR IN THE ENTIRE PACIFIC OCEAN, BUT IN CONTRAST TO A FEW WEEKS AGO DO NOT REACH 1 DEGREE C ANYWHERE. SST ANOMALIES IN THE NINO 3.4 REGION ARE HOVERING NEAR THE POSITIVE 0.5 C THRESHOLD. DYNAMICAL MODELS PREDICT SST ANOMALIES TO INCREASE SOMEWHAT IN THIS REGION USED FOR MONITORING THE ENSO STATE, SUGGESTING A GOOD CHANCE THAT EL NINO CONDITIONS WILL DEVELOP DURING FALL OF 2012. DYNAMICAL FORECASTS, HOWEVER, ARE WEAKER NOW THAN 1 AND ESPECIALLY 2 MONTHS AGO. STATISTICAL MODELS GENERALLY HAVE PREDICTED SMALLER SST ANOMALIES. WHILE IT IS UNCERTAIN AT THIS TIME HOW LARGE SST ANOMALIES WILL BE OR HOW MUCH THEY WILL ALTER THE LARGE SCALE CIRCULATION IMPACTING NORTH AMERICA IT NOW SEEMS UNLIKELY THAT A STRONG EL NINO WILL DEVELOP. THE OND 2012 TEMPERATURE OUTLOOK INDICATES ENHANCED CHANCES FOR ABOVE NORMAL TEMPERATURES FROM THE SOUTHWEST THROUGH THE GREAT PLAINS TO THE NORTHEAST, AND IN NORTHERN ALASKA. THIS IS SUPPORTED BY DYNAMICAL MODELS AND BY LOCAL SST ALONG THE SHORE OF NORTHERN ALASKA. THE OND 2012 PRECIPITATION OUTLOOK INDICATES AN INCREASED LIKELIHOOD FOR BELOW-MEDIAN PRECIPITATION FOR MUCH OF THE NORTHWEST CONUS, NORTHERN CALIFORNIA, EXTREME NORTHWESTERN NEVADA, NORTHERN IDAHO, AND THE ALASKA PANHANDLE BASED ON THE DYNAMICAL MODELS. ABOVE MEDIAN PRECIPITATION IS PREDICTED FROM SOUTHERN TEXAS ALONG THE GULF COAST TO THE SOUTHERN MID-ATLANTIC. 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 PACIFIC SST ANOMALIES ALONG THE EQUATOR EXCEED OR ARE NEAR 0.5 DEGREES C FROM INDONESIA TO THE SOUTH AMERICAN COAST, BUT THERE ARE NO ANOMALIES EXCEEDING POSITIVE 1.0 DEGREES C ANY LONGER ANYWHERE. THE AVERAGE HEAT CONTENT IN THE UPPER OCEAN NEAR THE EQUATOR HAS DECLINED DURING THE PAST MONTH. OCEAN TEMPERATURES BELOW THE SURFACE DOWN TO 100-125 METERS ARE NOW ABOVE AVERAGE OVER A VERY LARGE AREA, BUT RARELY MORE THAN 1 DEGREE C. AT GREATER DEPTHS STILL, WIDESPREAD NEGATIVE ANOMALIES HAVE APPEARED WITH A MAXIMUM OF -2 DEGREES C NEAR 155W AND 150 METER DEPTH. THE TROPICAL ATMOSPHERIC CIRCULATION APPEARS TO HAVE ONLY SMALL ANOMALIES IN OLR AND UPPER AND LOWER LEVEL WINDS AND NOT PARTICULARLY INDICATIVE FOR A WARM EVENT. THUS, NEUTRAL ENSO CONDITIONS CONTINUE, AT LEAST IN THE SHORT RUN. PROGNOSTIC DISCUSSION OF SST FORECASTS LATEST WEEKLY OBSERVATIONS PLACE THE NINO 3.4 INDEX AT ABOUT 0.50 C, WHILE THE JJA AVERAGE IS SLIGHTLY HIGHER AT 0.6. ALL OF THE MOST RECENT DYNAMICAL MODEL RUNS PREDICT POSITIVE ANOMALIES THROUGH JFM 2013, RANGING FROM A MAXIMUM OF +0.25 C TO MORE THAN +2.0 C. THE ENSEMBLE MEAN PEAKS AT LESS THAN 1 DEGREE C AROUND DECEMBER. THIS PEAK VALUE IS DOWN FROM THE FORECASTS MADE LAST MONTH AND IN JULY ESPECIALLY. ABOUT HALF OF THE STATISTICAL MODELS PREDICT ANOMALIES AROUND +0.5 C, BUT NONE EXCEEDS +0.8 C. BASED ON THESE FORECAST TOOLS, IT IS POSSIBLE THAT AN EL NINO EVENT OF WEAK AMPLITUDE WILL OCCUR LATER THIS FALL AND INTO LATE WINTER. FOR THE PHYSICAL IMPACT, THE THRESHOLD DEFINITION OF HALF A DEGREE IS SOMEWHAT ARBITRARY. SO A NON-EVENT OF 0.49 C MAY BE AS IMPORTANT FOR THE NORTH AMERICAN CLIMATE AS A WEAK EVENT OF 0.51. PROGNOSTIC TOOLS USED FOR U.S. TEMPERATURE AND PRECIPITATION OUTLOOKS WITH THE ADVANCE OF COUPLED ATMOSPHERE OCEAN MODELS WE NOW HAVE A SET OF ABOUT 10 MODELS, EACH WITH MANY RUNS, THAT IN GENERAL REFLECT SST ANOMALIES THAT ARE WEAKER THAN EXPECTED ONE AND TWO MONTHS AGO. WE DO MAINTAIN CONTINUITY AS MUCH AS IS REASONABLE WITH FORECASTS RELEASED LAST MONTH. THE PREVIOUS SET OF FORECASTS USED ENSO COMPOSITES STRONGLY. WE REVISED IN THE FOLLOWING WAY. FIRST, ENSO COMPOSITES HAVE BEEN DOWNPLAYED SOMEWHAT. SECOND AND THIRD, THE FORECAST WAS ADJUSTED TO REFLECT THE NMME AND IMME, AS WELL AS THE CONSOLIDATION WHERE AND WHEN DEEMED HELPFUL. THE OUTLOOKS FOR OND 2012 THUS PRIMARILY REFLECT DYNAMICAL MODEL FORECASTS INCLUDING THE CFSV2 AND IMME AND NMME FORECASTS, AS WELL AS DECADAL TIMESCALE TRENDS. THE CONSOLIDATION OF STATISTICAL TOOLS IS THE ONLY BASIS FOR FORECASTS FROM MAM 2013 ONWARD. WE THUS DOWNPLAYED SOMEWHAT THE ENSO IMPACT DURING WINTER AND TERMINATED THE ENSO IMPACT ONE MONTH EARLIER THAN IN LAST MONTH'S SET OF CPC SEASONAL FORECASTS. PROGNOSTIC DISCUSSION OF OUTLOOKS - OND 2012 TO OND 2013 TEMPERATURE THE OND 2012 TEMPERATURE OUTLOOK INDICATES ENHANCED CHANCES FOR ABOVE NORMAL TEMPERATURES FROM THE SOUTHWEST THROUGH THE GREAT PLAINS TO THE NORTHEAST, AND IN NORTHERN ALASKA. THIS IS SUPPORTED BY DYNAMICAL MODELS AND ALONG THE SHORE OF NORTHERN ALASKA ALSO BY LOCAL SST. TEMPERATURE OUTLOOKS FROM NDJ 2012-2013 THROUGH FMA 2013 SHOW INCREASED CHANCES OF ABOVE NORMAL TEMPERATURES ACROSS MUCH OF THE NORTHERN CONUS AND SOME AREAS WITH INCREASED CHANCES OF BELOW NORMAL TEMPERATURES IN SMALL PORTIONS OF THE SOUTHERN CONUS, DUE TO THE LIKELY INFLUENCE OF EL NINO CONDITIONS AS SEEN IN EMPIRICAL COMPOSITES AND AS MODELED IN NMME. AN EL NINO INCREASES THE PROBABILITIES FOR ABOVE NORMAL TEMPERATURES IN SOUTHERN PORTIONS OF ALASKA, WHILE TRENDS INCREASE THE CHANCES IN NORTHERN ALASKA. THE FORECAST FOR FMA 2013 REFLECTS A TRANSITION FROM EL NINO, NO MATTER HOW WEAK, TO NEUTRAL CONDITIONS BY THAT TIME. FORECASTS IN MAM 2013 AND LATER THROUGH OND 2013 REFLECT ALMOST EXCLUSIVELY DECADAL TRENDS. IN AREAS WITHOUT STRONG CLIMATE SIGNALS, EQUAL CHANCES FOR BELOW NORMAL, NEAR NORMAL, OR ABOVE NORMAL SEASONAL MEAN TEMPERATURES IS PREDICTED. PRECIPITATION THE OND 2012 PRECIPITATION OUTLOOK INDICATES AN INCREASED LIKELIHOOD FOR BELOW-MEDIAN PRECIPITATION FOR MUCH OF THE NORTHWEST CONUS, NORTHERN CALIFORNIA, EXTREME NORTHWESTERN NEVADA, NORTHERN IDAHO, AND THE ALASKA PANHANDLE BASED ON THE DYNAMICAL MODELS. ABOVE MEDIAN PRECIPITATION IS PREDICTED FROM SOUTHERN TEXAS ALONG THE GULF COAST TO THE SOUTHERN MID-ATLANTIC. ONCE, AND IF, EL NINO CONDITIONS ARE ESTABLISHED, THE EXTENSION OF THE SUB-TROPICAL JET ENHANCES THE CHANCES OF ABOVE MEDIAN PRECIPITATION ACROSS THE SOUTHERN CONUS FOR OND 2012 THROUGH FMA 2013, AND INCREASES THE LIKELIHOOD OF BELOW MEDIAN PRECIPITATION IN THE PACIFIC NORTHWEST AND THE CENTRAL MISSISSIPPI AND OHIO VALLEYS. WHILE WE PLAYED DOWN THESE ENSO IMPACTS SOMEWHAT WE KEPT ALL ENSO SIGNALS AS SEEN IN NMME WHICH IS COGNIZANT OF WEAKER PREDICTED SST ANOMALIES. IN GENERAL WE BACKED OFF FROM CHANCES OF ABOVE MEDIAN PRECIPITATION IN THE SOUTHWEST AND CALIFORNIA. THE DRYNESS IN THE NORTHWEST HAS ALMOST UNANIMOUS SUPPORT FORM ALL MODELS, SO WE EXTENDED THE AREAL COVERAGE, HOWEVER WITHOUT MAKING TWO CLASS CHANGES IN NORTHERN CALIFORNIA. THE ENSO STATE IS UNCERTAIN BEYOND FMA 2013, WITH WEAK SIGNALS FOR ANOMALOUS PRECIPITATION DUE TO DECADAL TRENDS. IN ALL, THERE ARE ALMOST NO SIGNALS FROM MAM - OND 2013. BELOW MEDIAN PRECIPITATION IS SLIGHTLY MORE LIKELY FOR THE PACIFIC NORTHWEST IN SUMMER 2013. FORECASTER: HUUG VAN DEN DOOL THE CLIMATIC NORMALS ARE BASED ON CONDITIONS BETWEEN 1981 AND 2010, FOLLOWING THE WORLD METEROLOGICAL ORGANIZATION CONVENTION OF USING THE MOST RECENT 3 COMPLETE DECADES AS THE CLIMATIC REFERENCE PERIOD. THE PROBABILITY ANOMALIES FOR TEMPERATURE AND PRECIPITATION BASED ON THESE NEW NORMALS BETTER REPRESENT SHORTER TERM CLIMATIC ANOMALIES THAN THE FORECASTS BASED ON OLDER NORMALS. 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 18 2012 1981-2010 BASE PERIOD MEANS WERE IMPLEMENTED EFFECTIVE WITH THE MAY 19, 2011 FORECAST RELEASE. $$