PROGNOSTIC DISCUSSION FOR LONG-LEAD SEASONAL OUTLOOKS NWS CLIMATE PREDICTION CENTER CAMP SPRINGS MD 830 AM EDT THU SEP 15 2005 SUMMARY OF THE OUTLOOK FOR NON-TECHNICAL USERS . . . . . . . . SEA SURFACE TEMPERATURES (SSTS) AND SUBSURFACE OCEAN TEMPERTURES ACROSS THE EQUATORIAL PACIFIC REMAIN CLOSE TO AVERAGE ACROSS THE ENTIRE BASIN. THIS PATTERN OF OCEAN TEMPERATURES HAS BEEN ACCOMPANIED BY STRONGER THAN AVERAGE LOW LEVEL EASTERLY WINDS AND NEAR AVERAGE CONVECTION. DESPITE SOME DISAGREEMENT AMONG THE STATISTICAL AND DYNAMICAL ENSO FORECASTS... CURRENT CONDITIONS AND RECENT OBSERVED TRENDS SUPPORT A CONTINUATION OF ENSO NEUTRAL CONDITIONS THROUGH THE END OF THE YEAR. ELSEWHERE SSTS THROUGHOUT THE TROPICAL NORTH ATLANTIC OCEAN EXTENDING INTO THE CARIBBEAN SEA CONTINUE TO BE WELL ABOVE AVERAGE. THESE ABNORMALLY WARM SSTS HAVE CONTRIBUTED TO A VERY ACTIVE HURRICANE SEASON. SOME MODELING STUDIES ALSO IMPLY THAT THEY MAY ALSO PLAY A ROLE IN THE PATTERNS OF TEMPERATURE AND PRECIPITATION ACROSS THE CONUS DURING THE UPCOMING SEASONS. THE OUTLOOKS FOR OND 2005 THROUGH MAM 2006 ARE BASED ON A WIDE ARRAY OF DYNAMICAL AND STATISTICAL TOOLS. OUTLOOKS FOR AMJ 2006 AND BEYOND ARE BASED MAINLY ON TRENDS WITH SOME INPUT FROM OTHER STATISTICAL TOOLS... WITH ENSO EXPECTED TO BE IN ITS NEUTRAL PHASE THROUGH AT LEAST SPRING 2006. THE MOST CONFIDENT SIGNALS ARE FOR ABOVE AVERAGE TEMPERATURES DURING THE FEW SEASONS AND AT LOCATIONS WHERE TRENDS ARE STRONG. . . . . . . . . BASIS AND SUMMARY OF THE CURRENT LONG-LEAD OUTLOOK 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 SSTS ALONG THE EQUATOR WERE GENERALLY NEAR THE LONG-TERM AVERAGE DURING AUGUST WITH THE WARMEST SSTS AND LARGEST DEPARTURES OBSERVED JUST TO THE WEST OF THE INTERNATIONAL DATE LINE. SUBSURFACE OCEAN TEMPERATURES THROUGHOUT THE EQUATORAL PACIFIC WERE SLIGHTLY ABOVE AVERAGE IN THE WESTERN AND FAR EASTERN PACIFIC AND 1-2 DEGREES CELSIUS BELOW AVERAGE NEAR 100 M DEPTH BETWEEN 150W AND 100W. ATMOSPHERIC INDICATORS SUCH AS THE LOW LEVEL WINDS AND CONVECTION IN THE EQUATORIAL PACIFIC ALSO REMAIN CLOSE TO AVERAGE AND SUGGEST... TOGETHER WITH THE OCEAN STATE ... THAT NEUTRAL ENSO CONDITIONS WILL LIKELY PREVAIL IN THE NEXT FEW MONTHS. THERE IS AN EXTENSIVE AREA OF ABOVE NORMAL SSTS IN THE (SUB)TROPICAL ATLANTIC OCEAN AND THE CARIBBEAN SEA. MODEL INDICATIONS FROM SOME EXPERIMENTAL RUNS INDICATE THESE VERY WARM ATLANTIC SSTS MAY CONTRIBUTE TO RIDGING OVER THE WESTERN CONUS. . . . . . . . . PROGNOSTIC DISCUSSION OF SST FORECASTS THE CONSENSUS OF SEVERAL MODELS USED AT CPC SHOWS SEASONAL MEAN NINO 3.4 SST ANOMALIES REMAINING VERY CLOSE TO THE LONG TERM AVERAGES THROUGH THE WINTER AND THE SPRING. SPREAD AMONG THE INDIVIDUAL TOOLS HAS DECREASED THIS MONTH... RANGING FROM +0.6 FROM THE CCA TO -0.4 FROM THE CFS. THIS DECREASE IN SPREAD INCREASES THE CONFIDENCE THAT SSTS ACROSS THE TROPICAL PACIFIC WILL REMAIN NEAR AVERAGE THROUGH THE EARLY PART OF 2006. PROGNOSTIC TOOLS USED FOR U.S. TEMPERATURE AND PRECIPITATION OUTLOOKS THE OUTLOOK FOR OND 2005 THROUGH MAM 2006 IS BASED ON THE MULTI-MODEL ENSEMBLE FROM IRI... THE CFS... AND STATISTICAL TOOLS... INCLUDING CCA... SMLR AND OCN. INPUT FROM CDC MODELS - WHICH FAVORS WARM AND DRY CONDITIONS OVER THE WESTERN TWO-THIRDS OF THE NATION - WAS CONSULTED. ECCA WAS USED FOR OND. OCN IS THE PRIMARY TOOL EXPLICITLY USED FROM MAM THROUGH OND 2006. BECAUSE ENSO IS WEAK ALL FORECASTS REFLECT INTERDECADAL TREND MORE THAN ANY OTHER FACTOR. A NEW FORECAST TOOL HAS BEEN DEVELOPED WHICH COMBINES THE CCA - THE OCN - THE SMLR AND A 15-MEMBER ENSEMBLE MEAN FROM THE CFS - USING THE KNOWN SKILL OF THE VARIOUS TOOLS TO FORM A WEIGHTED AVERAGE. THIS TOOL - CALLED CON - HELPS TO REDUCE THE UNCERTAINTY WHICH FORECASTERS CONFRONT WHEN THEY TRY TO SUBJECTIVELY COMBINE FORECAST TOOLS. THIS TOOL HAS BEEN USED IN THE TEMPERATURE AND PRECIPITATION FORECASTS THIS TIME. VERIFICATION OF THE TOOL OVER FORECASTS FROM THE 1995-2005 PERIOD INDICATE THAT THE TOOL SHOULD IMPROVE TEMPERATURE FORECASTS OVER THE CONUS. PRECIPITATION FORECASTS FROM THE CON HAVE NOT YET BEEN VERIFIED AND IT IS - THEREFORE - USED MUCH MORE CONSERVATIVELY THAN IT WAS FOR TEMPERATURE. . . . . . . . . PROGNOSTIC DISCUSSION OF OUTLOOKS - OND 2005 TO OND 2006 TEMPERATURE: THE MAJOR CHANGE FROM LAST MONTH TO THE OND 2005 FORECAST WAS AN EXPANSION OF THE REGION OF ABOVE AVERAGE TEMPERATURES THROUGHOUT THE WEST... ALTHOUGH THE REGION IN THE PACIFIC NORTHWEST WAS SHIFTED SOUTH. ALSO THE REGION OF ABOVE AVERAGE TEMPERATURES IN ALASKA WAS EXPANED TO ENCOMPASS MUCH OF CENTRAL AND WESTERN ALASKA. THE EXPANSION IN THE WEST WAS CONSISTENT WITH MANY OF THE MODELS FORCED BY WARM SUBTROPICAL ATLANTIC SSTS. DURING THE WINTER SEASONS... MODIFICATIONS INCLUDED AN EXPANSION OF ABOVE AVERAGE TEMPERATURES IN THE WEST DURING NDJ AND THE DECREASE IN ABOVE AVERAGE TEMPERATURES DURING DJF AND JFM OVER THE MIDWEST AND NORTHEAST. THE CHANGES IN THE MIDWEST AND NORTHEAST REFLECT THE CONTINUED UNCERTAINTY WITH POTENTIAL PHASE OF THE NAO DURING THE WINTER AS WELL AS CONFLICTS BETWEEN OCN - WHICH FAVORS ABOVE AVERAGE TEMPERATURES IN THESE REGIONS - AND INPUT FROM CDC... WHICH FAVORED AVERAGE TO BELOW AVERAGE. . . . . . . . . PRECIPITATION: CHANGES FROM LAST MONTHS FORECASTS ARE LESS EXTENSIVE FOR PRECIPITATION THAN THEY WERE FOR TEMPERATURE. FOR OND... SIGNALS FOR CONTINUED WETNESS OVER FLORIDA WERE WEAKER... AND THIS ABOVE AVERAGE AREA WAS REMOVED. AN EXTENSIVE AREA OF BELOW AVERAGE PRECIPITATION WAS INSERTED OVER THE THE SOUTHWEST... AS THE ECCA... THE IRI MULTI-MODEL... THE CFS... THE SMLR... AND THE CDC INPUT ALL FAVORED BELOW AVERAGE PRECIPITATION IN THE REGION. THE FORECASTS FOR BELOW AVERAGE PRECIPITATION IS CONTINUED IN PARTS OF THE SOUTHWEST THROUGH DJF 2005-2006... AS THE SMLR... THE CFS... AND INPUT FROM CDC CONTINUE TO SIGNAL DRIER THAN AVERAGE CONDITIONS. THE ONLY OTHER CHANGE TO THE SUITE OF SEASONAL PRECIPITATION OUTLOOKS OCCURRED IN FLORIDA... WHERE AN ENHANCED REGION OF ABOVE AVERAGE RAINFALL DURING JJA 2006 WAS INDICATED BY THE LONG TERM TREND . NOTE - AREAS OF UNCERTAINTY THAT FORMERLY WERE LABELED CL (CLIMATOLOGICAL PROBABILITIES) ARE NOW LABELED EC (EQUAL CHANCES). . . . . . . . . FORECASTER: M. HALPERT GLOSSARY AND DEFINITIONS: ANALOG (NATURAL ANALOG) - A WEATHER MAP THAT RESEMBLES ANOTHER WEATHER MAP - USUALLY FROM DIFFERENT YEARS BUT THE SAME SEASON IN THE HISTORICAL RECORD. THE CRITERION FOR SELECTING AN ANALOG IS OFTEN THE PATTERN CORRELATION BETWEEN THE MAPS. TWO MAPS WILL JUST BEGIN TO RESEMBLE EACH OTHER TO THE HUMAN EYE AT A PATTERN CORRELATION OF ABOUT 40%. TO BE USEFUL - ANALOGS NEED TO HAVE MUCH HIGHER CORRELATIONS TO THE ORIGINAL MAP THAN THAT - 80% OR MORE. ANALOGS ARE INCREASINGLY DIFFICULT TO FIND AS THE GEOGRAPHIC REGION BEING COMPARED INCREASES IN SIZE. PERFECT ANALOGS TO THE ENTIRE NORTHERN HEMISPHERE SIMPLY DO NOT EXIST - FOR PRACTICAL PURPOSES. THIS IS WHY SIMPLE ANALOG FORECAST METHODS DO NOT WORK VERY WELL. ANNUAL CYCLE - AT MOST LOCATIONS THE CLIMATE STATE VARIABLES - T - P - SST- WIND - AND OTHERS DISPLAY A REGULAR VARIATION WHICH FOLLOWS THAT OF THE ELEVATION OF THE SUN IN THE SKY. A GRAPH OF THE 30 YEAR AVERAGE OF A VARIABLE FOR EACH DAY OF THE YEAR VERSUS DATE SHOWS A WAVE-FORM WHICH - FOR T AT DES MOINES FOR EXAMPLE - RANGES SMOOTHLY FROM LOWEST VALUES IN THE WINTER TO HIGHEST VALUES IN THE SUMMER. ANOMALY - THE ARITHMETIC DIFFERENCE BETWEEN THE VALUE OF A VARIABLE AT A GIVEN PLACE AND TIME AND THE LONG-TERM AVERAGE (USUALLY 30 YEARS) FOR THE LOCATION AND TIME OF YEAR. AO - ARCTIC OSCILLATION - A MEASURE OF THE DIFFERENCE IN PRESSURE (AT SEA LEVEL) OR 500-HPA HEIGHT (IN THE MIDDLE TROPOSPHERE) BETWEEN THE NORTHERN POLAR REGION AND MIDDLE LATITUDES. WHEN PRESSURES AND HEIGHTS ARE ABOVE (BELOW) NORMAL AT HIGH LATITUDES AND BELOW (ABOVE) NORMAL AT MIDDLE LATITUDES - THE AO IS DEFINED AS NEGATIVE (POSITIVE) AND IS ASSOCIATED WITH BELOW (ABOVE) NORMAL TEMPERATURES OVER MIDDLE LATITUDES - INCLUDING THE CONUS. CA - CONSTRUCTED ANALOG - A LINEAR COMBINATION OF PAST OBSERVED ANOMALY PATTERNS SUCH THAT THE COMBINATION IS AS CLOSE AS DESIRED TO THE INITIAL STATE. A FORECAST IS OBTAINED BY PERSISTING THE WEIGHTS ASSIGNED TO EACH YEAR IN THE HISTORICAL RECORD AND LINEARLY COMBINING THE STATES FOLLOWING THE INITIAL TIME IN THE HISTORICAL YEARS. CAS - CONSTRUCTED ANALOG SOIL MOISTURE PREDICTION TECHNIQUE. CCA - CANONICAL CORRELATION ANALYSIS - A TECHNIQUE WHICH PREDICTS THE STATUS OF U.S. T AND P FOR SOME FUTURE TARGET SEASON USING THE MOST RECENT 4 NON- OVERLAPPING SEASONAL OBSERVATIONS OF TROPICAL PACIFIC SST - CIRCULATION AND U.S. T OR P TO CHARACTERIZE THE RECENT BEHAVIOR OF THE CLIMATE - AND PAST OBSERVATIONS TO PLACE RECENT BEHAVIOR INTO A HISTORICAL CONTEXT. CFS - CLIMATE FORECAST SYSTEM - A FULLY-COUPLED OCEAN-ATMOSPHERE FORECAST SYSTEM WHICH USES NO ADJUSTMENTS TO OCEAN-ATMOSPHERE FLUXES IN POST- PROCESSING (A ONE-TIER SYSTEM) DEVELOPED AT THE NATIONAL CENTERS FOR ENVIRONMENTAL PREDICTION. CLIMATOLOGY - THE 30-YEAR AVERAGE OF A VARIABLE - LIKE TEMPERATURE - AT A GIVEN LOCATION AND TIME OF YEAR. CON - A FORECAST TOOL IN WHICH FORECASTS FROM VARIOUS TOOLS ARE COMBINED IN A WEIGHTED AVERAGE. THE WEIGHTS FOR THIS AVERAGE ARE BASED ON THE KNOWN SKILL OF THE VARIOUS FORECAST TOOLS. . . . . . . . . CONUS - CONTERMINOUS UNITED STATES DYNAMICAL MODEL - A PREDICTION METHOD WHICH USES EQUATIONS DESCRIBING THE PHYSICAL BEHAVIOR OF A SYSTEM AND A COMPREHENSIVE SET OF CURRENT OBSERVATIONS OF THE VALUES OF THE VARIABLES DESCRIBING THE CURRENT STATE OF THE SYSTEM (INITIAL CONDITIONS) TO PREDICT THE VALUES OF THOSE VARIABLES A SHORT TIME-STEP IN THE FUTURE. THOSE VALUES ARE - IN TURN - USED AS THE INITIAL CONDITIONS FOR A SUBSEQUENT PREDICTION - AND SO ON - UNTIL THE DESIRED FUTURE PREDICTION TIME IS REACHED. EASTERLY WIND - WIND BLOWING FROM EAST TO WEST. EC - EQUAL CHANCES - THE PROBABILITY OF THE MOST LIKELY CATEGORY CANNOT BE DETERMINED AND THE EXPECTED LIKELIHOODS OF ABOVE - NORMAL AND BELOW DO NOT DIFFER FROM THEIR CLIMATOLOGICAL ODDS OF 33 1/3% EACH. EC REPLACES CL. ECCA - ENSEMBLE CCA. A MULTI-VARIATE STATISTICAL FORECAST BASED ON THE PAST PERFORMANCE OF THE CFS MODEL FORECAST USING THE MOST RECENT FORECAST AS THE PREDICTOR. EL NINO - THE WARM PHASE OF THE ENSO CYCLE ENSO - ACRONYM FOR EL NINO/SOUTHERN OSCILLATION GCM - GENERAL CIRCULATION MODEL - A GENERIC TERM APPLIED TO GLOBAL DYNAMICAL MODELS. ITCZ - INTERTROPICAL CONVERGENCE ZONE - A LINE WHERE THE SOUTHEASTERLY AND NORTHEASTERLY TRADE WINDS CONVERGE - CHARACTERIZED BY ENHANCED CONVECTION. IT MAY BE IN EITHER THE NORTHERN OR SOUTHERN HEMISPHERE - AND OCCASIONALLY A DOUBLE ITCZ MAY BE SEEN IN BOTH HEMISPHERES NOT FAR FROM THE EQUATOR. LA NINA - THE COLD PHASE OF THE ENSO CYCLE MJO - MADDEN-JULIAN OSCILLATION - ALSO CALLED TROPICAL INTRA-SEASONAL OSCILLATION - A DISTURBANCE IN TROPICAL CONVECTION - PRECIPITATION - WIND AND PRESSURE. MJO PRECIPITATION AND CLOUDINESS ARE ENHANCED ONLY IN REGIONS WHERE SSTS ARE VERY WARM - E.G. INDIAN OCEAN AND WEST PACIFIC. THE PRESSURE AND WIND DISTURBANCE ASSOCIATED WITH MJO IS OBSERVED TO MOVE FROM WEST TO EAST COMPLETELY AROUND THE GLOBAL TROPICS IN ABOUT 30 TO 60 DAYS. NAO - NORTH ATLANTIC OSCILLATION TELECONNECTION PATTERN - WHICH MAY BE CONSIDERED AS THE ATLANTIC HALF OF THE AO. NOTE THAT THE STATUS OF THE AO/NAO AND OTHER SLOWLY VARYING CIRCULATION MODES - WHILE VERY IMPORTANT IN DETERMINING THE TEMPERATURE AND PRECIPITATION REGIMES OVER THE U.S. - ARE UNPREDICTABLE BEYOND A WEEK OR TWO AHEAD AT BEST BY CURRENT TECHNOLOGY AND ARE NOT EXPLICITLY INCLUDED IN OUR FORECAST PROCESS AS RELIABLE PREDICTORS. NORTHERLY WIND - WIND BLOWING FROM NORTH TO SOUTH. OCN - OPTIMAL CLIMATE NORMALS - A FORECAST BASED ON PERSISTING THE AVERAGE OF THE LAST 10 YEARS FOR TEMPERATURE AND THE LAST 15 YEARS FOR PRECIPITATION. PNA - PACIFIC NORTH AMERICAN TELECONNECTION PATTERN. QBO - QUASI-BIENNIAL OSCILLATION - AN OSCILLATION OF THE WIND IN THE LOWER STRATOSPHERE BETWEEN EASTERLY AND WESTERLY WHICH REVERSES ON A NEARLY- 2 YEAR TIME SCALE. QBO IS ONE OF THE MOST REGULAR OSCILLATIONS KNOWN. SMLR - SCREENING MULTIPLE LINEAR REGRESSION - A TECHNIQUE WHICH SELECTS THE BEST SET OF PREDICTORS - FITTING THEM TO THE OBSERVATIONS TO CREATE EQUATIONS WHICH CAN BE USED TO MAKE PREDICTIONS. SOUTHERLY WIND - WIND BLOWING FROM SOUTH TO NORTH. STATISTICAL PREDICTIONS - PREDICTIONS BASED MAINLY ON LARGE OBSERVATIONAL DATA SETS. CCA - OCN - SMLR - CAS - CA ARE EXAMPLES OF THESE. TELECONNECTIONS - THESE GIVE THE HISTORICAL RELATIONSHIP BETWEEN A GIVEN POINT AND ALL OTHER POINTS OVER A LARGE AREA - LIKE THE NORTHERN HEMISPHERE - FOR A GIVEN TIME OF THE YEAR. THE POINTS ON THE MAP USUALLY CONSIST OF A SET OF MORE OR LESS EVENLY SPACED LOCATIONS CALLED GRID POINTS. TREND - AT A GIVEN LOCATION AND TIME OF YEAR - THE DIFFERENCE BETWEEN THE AVERAGE OF THE MOST RECENT 10 (15) YEARS OF OBSERVATIONS OF T (P) AND THE CLIMATOLOGY. WESTERLY WIND - WIND BLOWING FROM WEST TO EAST. ZONAL FLOW PATTERN - OCCURS WHEN 500-HPA CONTOURS LIE IN AN EAST-WEST DIRECTION PARALLEL TO LATITUDE CIRCLES WITH NEARLY PURE WEST-TO-EAST FLOW. -------------------------------------------------------------------------------- FOR A DESCRIPTION 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 FORMULATION AND SKILL OF THE CAS FORECASTS MAY BE FOUND AT: HTTP://WWW.CPC.NCEP.NOAA.GOV/SOILMST/FORECASTS.HTML (USE LOWER CASE LETTERS) NOTES - THESE CLIMATE OUTLOOKS ARE INTENDED FOR USE PRIOR TO THE START OF THEIR VALID PERIODS. 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 20 2005. 1971-2000 BASE PERIOD MEANS WERE IMPLEMENTED EFFECTIVE WITH THE MAY 17 2001 FORECAST RELEASE. $$