PROGNOSTIC DISCUSSION FOR LONG-LEAD SEASONAL OUTLOOKS NWS CLIMATE PREDICTION CENTER CAMP SPRINGS MD 300 PM EDT THU OCTOBER 16 2003 . . . . . . . . SUMMARY OF THE OUTLOOK FOR NON-TECHNICAL USERS THE SEASONAL OUTLOOK REFLECTS THE PRESENCE OF LONG TERM TRENDS ON U.S. TEMPERATURE AND PRECIPITATION...STATISTICAL FORECAST TOOLS...WITH SOME INPUT FROM NUMERICAL MODELS DURING THE FIRST SEVERAL SEASONS...AND THE LIKELY CONTINUATION OF ENSO NEUTRAL CONDITIONS IN THE TROPICAL PACIFIC DURING THE NEXT SEVERAL MONTHS. THE RAPID COOLING TREND TOWARDS LA NINA IN THE EQUATORIAL PACIFIC DURING JANUARY THROUGH MAY WAS FOLLOWED BY WARMING DURING JUNE AND EARLY JULY. BY NOW...MID-OCTOBER...SURFACE AND SUBSURFACE TEMPERATURES IN THE EQUATORIAL PACIFIC ARE SLIGHTLY ABOVE THE LONG TERM AVERAGE. A MINOR WARM EVENT FOR WINTER 2003/04 IS POSSIBLE SYNOPTICALLY BUT FOR NOW WE ASSUME NEUTRAL CONDITIONS. THEREFORE...EXCEPT FOR U.S. AREAS WITH STRONG TRENDS...BOTH PROBABILITIES AND AREA COVERED BY NON-EC PROBABILITIES IS RELATIVELY LOW IN THIS SET OF FORECASTS. THE OUTLOOK FOR NOVEMBER THROUGH JANUARY 2003/04 CALLS FOR ABOVE NORMAL TEMPERATURES OVER THE SOUTHWEST AND EXTREME SOUTHERN FLORIDA. NDJ PRECIPITATION IS EXPECTED TO BE BELOW MEDIAN OVER ARIZONA AS WELL AS OVER FLORIDA AND SOUTH GEORGIA. ABOVE MEDIAN PRECIPITATION IS EXPECTED OVER NORTH TEXAS AND SOUTHERN OKLAHOMA PLUS PORTIONS OF ADJACENT STATES. . . . . . . . . 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 AS OF MID-OCTOBER WEEKLY AVERAGES OF SST SHOW POSITIVE ANOMALIES ALONG THE EQUATOR IN THE PACIFIC FROM A FEW TENTHS TO 1 WHOLE DEGREE C. THE LARGEST ANOMALIES SHIFT AROUND IN RESPONSE TO WIND EVENTS. OVERALL THE TRADE WINDS CONTINUE TO BE SLIGHTLY WEAKER THAN AVERAGE. NINO34 IS CURRENTLY LARGER THAN +0.5 I.E. LARGER THAN IT HAS BEEN MOST OF THE SUMMER. DIAGNOSTICALLY WE ARE CLOSE TO A BORDERLINE WEAK EL NINO. AS FAR AS WE CAN TELL THE PATTERN OF CONVECTION IN THE TROPICS HAS NOT YET FOUND A LONGITUDE AT WHICH TO BECOME STATIONARY - SOMETHING WHICH IS REQUIRED IN ORDER TO PREDICT THE IMPACTS OF THE CONVECTION ON THE LARGE-SCALE CIRCULATION DURING THE WINTER. . . . . . . . . PROGNOSTIC DISCUSSION OF SST FORECASTS FORECASTS FROM MULTIPLE MODELS GIVE A RANGE OF POSSIBLE FUTURE SST PATTERNS IN THE TROPICAL PACIFIC ALTHOUGH MOST PROJECTIONS FALL WITHIN THE ENSO-NEUTRAL RANGE...A NINO 3.4 SST ANOMALY WITHIN THE RANGE OF -0.5C TO +0.5C. TO SEE THESE FORECASTS GO TO: http://www.cpc.ncep.noaa.gov/products/predictions/90day/tools/briefing/plume.gif A CONSOLIDATION FORECAST OF IN-HOUSE TOOLS INDICATES THAT NINO 3.4 SST ANOMALIES WILL REMAIN NEAR ZERO THROUGH SPRING 2004. CONFIDENCE IN THE SST FORECAST IS HIGH THROUGH NEXT WINTER AND DECREASES THEREAFTER. SSTA FORECASTS FOR THE NINO 3.4 REGION BY MODELS RUN IN OTHER CENTERS GENERALLY FALL IN THE ENSO-NEUTRAL RANGE AS WELL. AS A MATTER OF PROBABILTY FORECAST THIS DOES NOT RULE OUT A WEAK WARM EVENT...SO STAY TUNED. PROGNOSTIC TOOLS USED FOR U.S. TEMPERATURE AND PRECIPITATION OUTLOOK THE STATISTICAL TOOLS...CCA - OCN - SMLR...WERE CONSULTED AT ALL LEAD TIMES. DYNAMICAL MODEL FORECASTS FROM NCEP AND OTHER FORECAST CENTERS - IRI AND CDC- WERE EXAMINED FOR THE PERIOD NDJ 2003 THROUGH FMA 2004. CCA AND OCN TEMPERATURE FORECASTS WERE OFTEN CONSIDERED TOGETHER AS A CONSOLIDATION OF THESE TWO TOOLS AND WERE USED FOR THOSE AREAS AND PROJECTION TIMES WHERE THEY HAD USEFUL STATISTICAL SIGNIFICANCE. AS AN ALTERNATIVE WE ALSO USED TREND ADJUSTED ENSO COMPOSITES. CURRENTLY THE ODDS OF ENSO-NEUTRAL CONDITIONS STAND AT ABOUT 75%. . . . . . . . . PROGNOSTIC DISCUSSION OF OUTLOOKS - NDJ 2003 TO NDJ 2004 TEMPERATURE: WE CONSIDERED NEGATIVE ANOMALIES FOR THE NORTHEAST WHICH IS A POSSIBILITY IF CONVECTION WERE TO BECOME SETTLED NEAR OR WEST OF THE DATELINE AND A + PNA SETS UP. HOWEVER - IN THE FACE OF TRENDS FOR WARM AND THE UNCERTAINTY ABOUT A WEAK WARM EVENT WE OPTED FOR EC IN MUCH OF THE EAST. FOR NDJ THE TREND INDICATES POSITIVE ANOMALIES CENTERED OVER PARTS OF THE SOUTHWEST - SOUTHERN ALASKA - AND FLORIDA. IN MANY AREAS THE INDICATIONS FOR WARMTH ARE SUPPORTED BY CCA...SMT... AND THE TREND-ADJUSTED ENSO-NEUTRAL TEMPERATURE PATTERN. FROM DJF THROUGH AMJ TEMPERATURE FORECASTS ARE BASED PRIMARILY UPON CCA... OCN...SMT...WITH SOME INPUT FROM A COMPOSITE OF PAST CASES FOR TREND-ADJUSTED ENSO-NEUTRAL CONDITIONS. WARMER THAN AVERAGE TEMPERATURES ARE PREDICTED IN ALASKA BEGINNING IN DJF AND LASTING THROUGH SUMMER 2004 DUE TO OCN. OVER THE CONUS THE STRONGEST MOST CONFIDENT INDICATIONS - ALL WARM - ARE FOUND MAINLY IN THE SOUTH AND SOUTHWEST DURING WINTER...IN THE SOUTHWEST AND WEST IN SPRING...AND IN THE SOUTH AND SOUTHWEST AGAIN IN SUMMER. TRENDS ALONE...AS WELL AS CCA...WOULD FAVOR MUCH OF THE EASTERN HALF OF THE NATION TO HAVE ABOVE NORMAL TEMPERATURES DURING THE WINTER SEASONS...BUT THE ENSO-NEUTRAL COMPOSITES AND UNCERTAINTY IN THE AO AND NAO CAUSED US TO PUT EC IN SOME OF THOSE REGIONS. FORECASTS FOR BELOW IN THE DAKOTAS IN MAM AND AMJ ARE DUE TO TRENDS. FORECASTS BEGINNING WITH MJJ ARE BASED LARGELY ON OCN AND CCA FORECASTS...AND FOR THE SUMMER 2004 SEASONS INDICATE WARMTH OVER THE SOUTHWEST...SOUTHEAST... AND PACIFIC COAST FROM OCN WITH SOME SUPPORT FROM CCA. . . . . . . . . PRECIPITATION: ABOVE-MEDIAN PRECIPITATION IS FORECAST FOR NDJ IN PORTIONS OF THE GREAT PLAINS AND LOWER MISSISSIPPI VALLEY BASED ON OCN. INDICATIONS FOR BELOW MEDIAN PRECIPITATION OVER PORTIONS OF THE SOUTHWEST WERE ALSO BASED ON OCN...TREND-ADJUSTED ENSO-NEUTRAL CONDITIONS...AND CAS. WE ADDED A BELOW-MEDIAN PRECIP AREA FOR FLORIDA AND SOUTHERN GEORGIA. THIS IS SUPPORTED NOT ONLY BY TRENDS BUT ALSO BY COUNTLESS MODELS. THIS MAY SEEM A LA NINA SIGNAL BUT UPON FURTHER ANALYSIS THIS HAPPENS MAINLY IF CONVECTION STAYS A CERTAIN DISTANCE WEST OF THE DATE LINE - AS INDICTED BY MODEL STUDIES. THE AREA OF ABOVE-MEDIAN PRECIPITATION CENTERED OVER NORTH-EASTERN TEXAS FROM NDJ THROUGH JFM WAS INDICATED BY OCN...TREND COMPOSITES FOR ENSO-NEUTRAL CONDITIONS...AND CCA. AN AREA OF ABOVE-MEDIAN PRECIPITATION IS FORECAST FOR THE PACIFIC NORTHWEST DURING AMJ AND MJJ BASED ON OCN...TREND COMPOSITES FOR ENSO-NEUTRAL CONDITIONS...AND CCA. THERE WERE NO RELIABLE PRECIPITATION SIGNALS FOR JJA THROUGH SON 2004...WITH THE EXCEPTION OF DRYNESS IN PORTIONS OF THE FAR WEST DURING JAS AND WETNESS NEAR THE NEBRASKA WYOMING BORDER IN ASO AND SON INDICATED BY THE TREND-ADJUSTED ENSO-NEUTRAL COMPOSITES WITH SOME SUPPORT FROM OCN. BY OND AND NDJ 2004 SOME OF THE TRENDS FOR WET RETURN TO THE SOUTHERN PLAINS. FORECAST INDICATIONS FOR PRECIPITATION ARE UNCERTAIN IN MOST OF ALASKA...AND WITH THE EXCEPTION OF STRONGLY-FORCED STABLE COLD SEASON PATTERNS DURING EL NINO EVENTS...USUALLY HAVE RATHER LOW SKILL ESPECIALLY IN THE WARM SEASONS. THEREFORE THE ENTIRE STATE WAS LEFT EC FOR PRECIPITATION AT ALL LEADS. NOTE - AREAS OF UNCERTAINTY THAT FORMERLY WERE LABELED CL (CLIMATOLOGICAL PROBABILITIES) ARE NOW LABELED EC (EQUAL CHANCES). . . . . . . . . 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. 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. CLIMATOLOGY - THE 30-YEAR AVERAGE OF A VARIABLE - LIKE TEMPERATURE - AT A GIVEN LOCATION AND TIME OF YEAR. . . . . . . . . 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. 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. LA NINA - THE COLD PHASE OF THE ENSO CYCLE MJO - MADDEN-JULIAN OSCILLATION - ALSO CALLED TROPICAL INTRA-SEASONAL OSCILLA- TION - 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. 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 US - ARE UNPREDICTABLE BY CURRENT TECHNOLOGY AND ARE NOT EXPLICITLY INCLUDED IN OUR FORECAST PROCESS. 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. -------------------------------------------------------------------------------- . . . . . . . . FORECASTER: H. VAN DEN DOOL 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 NOV 20 2003. 1971-2000 BASE PERIOD MEANS WERE IMPLEMENTED EFFECTIVE WITH THE MAY 17 2001 FORECAST RELEASE. $$