PROGNOSTIC DISCUSSION FOR LONG-LEAD SEASONAL OUTLOOKS NWS CLIMATE PREDICTION CENTER CAMP SPRINGS MD 830 AM EDT THU SEPTEMBER 16 2004 . . . . . . . . SUMMARY OF THE OUTLOOK FOR NON-TECHNICAL USERS CURRENT OBSERVATIONS INDICATE THAT WE ARE IN THE EARLY STAGES OF A WARM EPISODE (EL NINO) OVER THE EQUATORIAL PACIFIC AND A MAJORITY OF SEA SURFACE TEMPERATURE (SST) PREDICTION TOOLS INDICATE THAT AT LEAST WEAK EL NINO CONDITIONS WILL CONTINUE FROM THIS FALL THROUGH AT LEAST THE FIRST FEW MONTHS OF 2005. THERE IS A SLIGHT CHANCE THAT THE EL NINO COULD REACH MODERATE INTENSITY OR WEAKEN BACK TO NEUTRAL STATUS... BUT THE CONSENSUS AMONG STATISTICAL AND DYNAMICAL MODEL PREDICTIONS INDICATES THAT THREE-MONTH AVERAGED SST ANOMALIES IN THE EAST CENTRAL EQUATORIAL PACIFIC AVERAGED OVER THE REGION BOUNDED BY 120W TO 170W AND WITHIN 5 DEGREES OF THE EQUATOR (NINO 3.4 REGION) WILL MOST LIKELY REMAIN IN THE RANGE OF +0.5 TO +1.0 DEG C FROM OND 2004 THROUGH MAM 2005. AFTER MAM 2005 THE OUTLOOK BECOMES MORE UNCERTAIN... BUT MOST MODELS INDICATE A WEAKENING AND EVENTUAL END OF THE WARM EPSIODE LATER IN 2005. UNCERTAINTIES ABOUT THE STRENGTH AND LOCATION OF THE ANTICIPATED ABNORMALLY WARM TROPICAL PACIFIC SSTS COME INTO PLAY FOR THIS FORECAST... ALTHOUGH THE CONSENSUS OF MOST MODELS... BOTH STATISTICAL AND DYNAMICAL... IS THAT THERE WILL BE A LARGE AREA OF ABOVE NORMAL SSTS NEAR AND EAST OF THE DATE LINE BUT THAT THERE WILL NOT BE SIGNIFICANTLY ABOVE NORMAL SSTS NEAR THE COAST OF SOUTH AMERICA. IT SHOULD BE NOTED THAT THE PATTERN AND SIZE OF SST ANOMALIES IN THE TROPICAL PACIFIC STRONGLY INFLUENCES THE MIDDLE LATITUDE IMPACTS OF EL NINO... ESPECIALLY DURING THE COLD SEASON. BASIN-WIDE... OR CLASSICAL STRONG EL NINOS LIKE THOSE OF 1982-83 AND 1997-98 HAVE A PATTERN OF ABNORMALLY WARM SSTS WHICH EXTEND ALL THE WAY FROM THE DATE LINE TO THE COAST OF PERU. IMPACTS OF SUCH EL NINOS OFTEN INCLUDE ABNORMAL WETNESS FROM CALIFORNIA TO FLORIDA ASSOCIATED WITH AN ACTIVE SUBTROPICAL JET STREAM AND EASTWARD EXTENSION OF THE PACIFIC JET...RESPECTIVELY...AND ABNORMAL DRYNESS CENTERED ON MONTANA AND THE OHIO VALLEY. THESE EVENTS ARE ALSO CHARACTERIZED BY ABNORMALLY WARM TEMPERATURES ACROSS AT LEAST THE NORTHERN HALF OF THE U.S. CENTRAL PACIFIC EL NINOS...LIKE THOSE IN 1963-64, 1968-69 AND 2002-03 ARE CHARACTERIZED BY WEAK SST ANOMALIES IN THE EASTERN PACIFIC AND ABNORMALLY WARM SSTS ONLY IN THE CENTRAL TROPICAL PACIFIC... AND THE U.S. TEMPERATURE RESPONSE IS USUALLY COLDER THAN NORMAL OVER THE SOUTHEAST AND A MUCH LESS RELIABLE HEAVY PRECIPITATION SIGNAL ACROSS THE SOUTHERN U.S. .. ESPECIALLY IN CALIFORNIA. . . . . . . . . SOME EL NINO RELATED INFLUENCE ON U.S. CLIMATE IS LIKELY FOR THE UPCOMING WINTER... AND A SLIGHT INCREASE IN THE ODDS IN FAVOR OF EL NINO IMPACTS ARE INDICATED IN THE LONG-LEAD OUTLOOKS BETWEEN OND 2004 AND MAM 2005. FOR LEAD TIME BEYOND MAM 2005 THE OUTLOOK PRIMARILY REFLECTS LONG TERM TEMPERATURE AND PRECIPITATION TRENDS. . . . . . . . . THE OUTLOOK FOR OND 2004 IS BASED ON INDICATIONS FROM WARMING TRENDS IN THE SOUTHWESTERN U.S... WITH ABOVE NORMAL TEMPERATURES ANTICIPATED ALONG THE U.S. WEST COAST AND IN COASTAL ALASKA PRIMARILY DUE TO ABNORMALLY WARM SSTS IN THE EASTERN NORTH PACIFIC OCEAN AND GULF OF ALASKA. AS THE SEASONS PROGRESS INTO WINTER... THE TEMPERATURE FORECASTS REFLECT EL NINO COMPOSITES IN COMBINATION WITH TRENDS AND INDICATIONS FROM OTHER TOOLS... ESPECIALLY THE NEWLY OPERATONAL NCEP CFS MODEL AND THE IRI MULTI-MODEL FORECASTS. TEMPERATURES IN THE SOUTHEASTERN U.S. ARE OFTEN COOLER FOR WEAK EL NINOS WITH WARM CENTRAL EQUATORIAL PACIFIC SSTS THAN FOR THEIR MODERATE AND STRONGER COUNTERPARTS WHOSE WARM SST ANOMALIES EXTEND TO THE COAST OF SOUTH AMERICA. THEY ALSO TEND TO BE COOLER WHEN TEMPERATURES OVER THE INDIAN OCEAN ARE NOT WELL ABOVE NORMAL AS THEY HAD BEEN UNTIL RECENTLY. THUS FORECASTS FOR THE EASTERN U.S. INCLUDE SOME INDICATIONS OF BELOW NORMAL TEMPERATURES OVER THE SOUTHEASTERN U.S. DURING THE WINTER SEASONS. FOLLOWING EL NINO COMPOSITES AND MANY OF THE MODEL INDICATIONS... TEMPERATURES OVER THE NORTHERN GREAT PLAINS ARE PREDICTED TO BE ABOVE NORMAL... BUT ONLY MARGINALLY ABOVE CLIMATOLOGICAL PROBABILITIES BECAUSE THIS AREA HAS OFTEN EXPERIENCED BELOW NORMAL TEMPERATURES WITH WEAK EL NINOS IN THE PAST. TEMPERATURES OVER THE NORTHWESTERN U.S. AND ALASKA ARE FORECAST TO BE ABOVE NORMAL TO REFLECT INCREASED CHANCES OF WARMER THAN NORMAL CONDITIONS IN EL NINO YEARS... AND ARE SUPPORTED BY MOST DYNAMICAL MODEL FORECASTS. EXPECTATION THAT THE LARGE AREA OF WELL ABOVE NORMAL TEMPERTURES OVER THE EASTERN PACIFIC WILL NOT DISSIPATE SOON LEADS TO FORECASTS OF ABOVE NORMAL TEMPERATURES OVER CALIFORNIA AS WELL. FOR AMJ 2004 AND BEYOND THE FORECAST REFLECTS MAINLY TRENDS TOWARDS WARMER THAN NORMAL TEMPERATURES OVER MUCH OF THE WEST IN THE SPRING... INCLUDING THE SOUTH CENTRAL AND SOUTHEASTERN U.S. IN SUMMER... AND ABOVE NORMAL TEMPERATURES EXTENDING INTO THE FALL OVER SOUTH FLORIDA AND THE SOUTHWESTERN U.S. SOME OF THE TREND-BASED TOOLS SUGGEST BELOW NORMAL OVER THE NORTH-CENTRAL STATES... ALTHOUGH NOT WITH MUCH CONFIDENCE. SINCE THE EXTENSIVE STRONGLY BELOW NORMAL TEMPERATURES OF THE PAST SUMMER HAVE NOT YET BEEN INCLUDED IN THE DEPENDENT DATA FOR THIS TOOL... IT WAS THOUGHT THAT THERE PROBABLY WOULD BE A STRONG ENOUGH CHANCE FOR BELOW NORMAL TEMPERATURES TO INDICATE SOME COOLNESS OVER THE NORTHERN GREAT PLAINS AND THE UPPER MISSISSIPPI VALLEY. . . . . . . . . PRECIPITATION FOR OND 2004 REFLECTS LONG TERM TRENDS FOR ABOVE MEDIAN RAINFALL OVER MOST OF FLORIDA AND PARTS OF ADJACENT STATES. SOME DYNAMICAL MODELS PREDICT ABOVE-MEDIAN PRECIPITATION FOR THE ALASKAN PANHANDLE IN THE LATE FALL AND EALY WINTER... WHICH APPEARS TO BE ALSO SUPPORTED BY ABOVE NORMAL SSTS. THE WINTER-TIME PRECIPITATION PATTERN OF GENERALLY WET CONDITIONS ACROSS THE SOUTHERN U.S. AND DRY CONDITIONS IN MUCH OF THE NORTHERN U.S. AND THE TENNESSEE VALLEY REFLECTS CLASSICAL EL NINO CONDITIONS... ALTHOUGH WITH MUCH LESS CONFIDENCE THAN WOULD BE GIVEN IN A STRONGER EVENT. SOME DYNAMICAL MODEL FORECASTS AND OBSERVED PRECIPITATION ASSOCIATED WITH HISTORICAL WEAK EL NINO EVENTS CONTRADICT THE SIGNAL FOR ABOVE MEDIAN PRECIPITATION AMOUNTS IN EASTERN NEW MEXICO AND WESTERN TEXAS ASSOCIATED WITH CLASSICAL STRONG EL NINOS... SO WET CONDITIONS IN THE SOUTH-CENTRAL U.S. IN THIS MONTHS FORECAST ARE CONFINED TO MAINLY EASTERN AND SOUTHERN TEXAS WHERE TRENDS ARE IN THEIR FAVOR AND THERE WAS SUPPORT FROM MANY OF THE DYNAMICAL MODELS. DRY CONDITIONS ALONG THE NORTHERN STATES ARE FROM ENSO COMPOSITES... WHICH ALSO ARE ONLY SLIGHTLY FAVORED IN WEAK ENSO EVENTS. THERE IS SOME ADDITIONAL SUPPORT FROM STATISTICAL FORECAST TOOLS AND TRENDS FOR DRY WINTERTIME CONDITIONS IN MONTANA. THE PRECIPITATION FORECAST FOR THE SOUTHWESTERN U.S. IS PARTICULARLY PROBLEMATIC... WHERE THE CHANCES FOR WET CONDITIONS INCREASE SLIGHTLY FOR WEAK EL NINO CONDITIONS WHILE THE ODDS FOR DRY CONDITIONS REMAIN NEARLY THE SAME AS FOR NEUTRAL CONDITIONS. FOR THE WARM SEASONS OF 2005 THE OUTLOOK REFLECTS PRECIPITATION TRENDS... WHICH ARE GENERALLY MODEST IN SIZE AND ONLY IN LIMITED PORTIONS OF THE WEST. WET CONDITIONS ARE INDICATED FOR PARTS OF THE PACIFIC NORTHWEST DURING LATE SPRING AND EARLY SUMMER WHILE DRY CONDITIONS ARE INDICATED OVER PARTS OF THE GREAT BASIN IN JAS AND ASO. TRENDS HINTING AT BELOW MEDIAN PRECIPITATION OVER THE UPPER RIO GRANDE VALLEY FOR ASO AND SON AND ABOVE MEDIAN PRECIPITATION IN FLORIDA FOR THE SEASONS JAS THROUGH SON 2005 AND OVER EASTERN TEXAS FOR OND WERE ALSO FOLLOWED. . . . . . . . . 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 THE MOST RECENT WEEKLY MEAN SHOWS THAT SSTS ARE MORE THAN 1 C ABOVE NORMAL ALONG AND NEAR THE EQUATOR FROM 160E TO 135W. SSTS ALONG AND JUST SOUTH OF THE EQUATOR NOW AVERAGE WITHIN AROUND 0.5 DEGREE C OF NORMAL FROM JUST OFF THE SOUTH AMERICAN COAST TO AROUND 125W. SUB-SURFACE OCEAN TEMPERATURES ALONG THE EQUATOR ARE SUBSTANTIALLY ABOVE NORMAL OVER MOST OF THE EAST-CENTRAL PACIFIC FROM THE SURFACE TO OVER 150 METERS DEPTH... WITH THE AXIS OF MAXIMUM ANOMALIES SLOPING UPWARDS FROM AROUND 150 METERS DEPTH IN THE CENTRAL PACIFIC TO 50 METERS DEPTH OVER THE EASTERN PACIFIC NEAR 110W. VERY LITTLE BELOW NORMAL WATER REMAINS AT ANY DEPTH OVER THE EASTERN PACIFIC. SO FAR THERE ARE FEW SIGNS OF ANY ANOMALOUS CONVECTION ASSOCIATED WITH THE WARM SSTS AND TRADE WINDS APPEAR PRIMARILY INFLUENCED BY INTRASEASONAL ACTIVITY. . . . . . . . . PROGNOSTIC DISCUSSION OF SST FORECASTS A CONSOLIDATION FORECAST OF IN-HOUSE TOOLS INDICATES THAT NINO 3.4 SST ANOMALIES WILL REMAIN CLOSE TO THE AUGUST AVERAGE OF ABOUT +.7 C FROM EARLY FALL THROUGH THE WINTER SEASON INTO SPRING BEFORE SLOWLY DECREASING IN THE LATE SPRING AND SUMMER MONTHS OF 2005. ENSEMBLE PREDICTIONS FROM THE NEW CFS MODEL... AND STATISTICAL PREDICTIONS FROM CCA... CA... AND THE MKV MODEL PREDICT THE NINO 3.4 SSTS ANOMALIES IN AN ENVELOPE BETWEEN +0.3 AND +1.2 DEGREES C THROUGH MAM 2005... WITH MOST BETWEEN 0.5 AND 1.0 DEG C MOST MODELS PREDICT THE POSITIVE SST ANOMALIES IN DJF 2004-05 TO BE RESTRICTED TO A RELATIVELY NARROW AREA MAINLY IN THE CENTRAL PACIFIC. THE MAJORITY OF MODELS PREDICT ABOVE NORMAL SSTS TO EXTEND TO THE SOUTH AMERICAN COAST BY DJF... ALTHOUGH NONE PREDICT THE EXTENSIVE AREAS OF WELL ABOVE NORMAL SSTS IN THE PACIFIC NEAR THE SOUTH AMERICAN COAST ASSOCIATED WITH STRONG WARM EVENTS. PROGNOSTIC TOOLS USED FOR U.S. TEMPERATURE AND PRECIPITATION OUTLOOK THIS OUTLOOK IS BASED ON INDICATIONS FROM AN ASSORTMENT OF STATISTICAL TOOLS AND DYNAMICAL MODEL FORECASTS. EL NINO COMPOSITES BASED ON MODERATE AND STRONG EVENTS... MODIFIED BY COMPOSITES FOR WEAK WARM EVENTS... WERE CONSULTED FROM OND 2004 TO MAM 2005. A TWO-TIER FORECASTING SYSTEM BASED ON SIX MODELS PROVIDED BY CDC WAS CONSULTED... ALONG WITH DYNAMICAL MULTI-MODEL ENSEMBLES FROM IRI AND DYNAMICAL MODEL FORECASTS FROM NCEPS NEWLY OPERATIONAL CFS MODEL PROVIDED INPUT THROUGH JFM 2005. THE NEW CFS MODEL WHICH BECAME OPERATIONAL ON AUGUST 24 2004 PROVIDES FORECASTS THROUGH MMA 2005. CCA... OCN AND SMLR GUIDANCE WERE CONSULTED FOR ALL LEAD TIMES. THE CONSTRUCTED ANALOG SOIL MOISTURE MODEL (CAS) INDICATED A PATTERN QUITE DIFFERENT FROM THE GOOD CONSENSUS OF MOST OF THE OTHER TOOLS... AND WAS THUS DISREGARDED... AS IT ALSO HAS LESS A PRIORI SKILL ANYWAY DURING THE FALL AND WINTER. ANY EL NINO IMPACTS WILL DEPEND CRITICALLY ON THE EVOLUTION OF THE SSTS IN THE EASTERN PACIFIC AND THE COUPLING BETWEEN THE ATMOSPHERE AND SST ANOMALIES. THE LOW PROBABILITIES ASSOCIATED WITH THESE OUTLOOKS... PARTICULARLY FOR PRECIPITATION... SHOW REGIONS WHERE THERE IS A CHANCE FOR ENSO IMPACTS. IN SUBSEQUENT MONTHS THESE PROBABILITIES WILL LIKELY BE REVISED TO REFLECT THE EVOLUTION OF THE SSTS AND WHETHER THEY MAKE IT MORE OR LESS LIKELY FOR ENSO RELATED IMPACTS. . . . . . . . . PROGNOSTIC DISCUSSION OF OUTLOOKS - OND 2004 TO OND 2005 TEMPERATURE: FOR OND 2004 THE IRI MULTI MODEL ENSEMBLE PREDICTION SUGGESTS ABOVE NORMAL TEMPERATURES FOR THE EDGES OF THE WESTERN U.S. AND MOST OF ALASKA... BUT THE CFS MODEL GAVE MORE EXTENSIVE COVERAGE OF ABOVE NORMAL TEMPERATURES IN THE NORTHWEST... AND SOME BELOW NORMAL ALONG THE RIO GRANDE VALLEY. OCN INDICATES ABOVE NORMAL TEMPERATURES OVER THE SOUTHWESTERN U.S. FOR OND 2004. AS THE SEASONS PROGRESS TOWARDS WINTER... ABOVE NORMAL TEMPERATURES ARE PREDICTED TO EXPAND OVER THE WESTERN AND NORTHWESTERN PORTIONS OF THE U.S. AND SPREAD EASTWARD. THIS PATTERN ALSO AGREES WITH CFS MODEL AND ENSO COMPOSITES. THE CFS MODEL PREDICTS NOTABLY BELOW TEMPERATURES IN THE SOUTHERN AND EASTERN U.S. THROUGH MAM 2005. THESE ARE SUPPORTED BY WEAK EL NINO COMPOSITES. HOWEVER... IN VIEW OF STRONG WARMING TRENDS IN RECENT YEARS... AND CONTRARY INDICATIONS FROM CCA... IT IS STILL TOO EARLY TO COMMIT TO A FORECAST OF BELOW NORMAL FOR THE NORTHEASTERN U.S... AND EQUAL CHANCES WERE GIVEN. BELOW NORMAL TEMPERATURES WERE FORECAST FOR PORTIONS OF THE SOUTHEASTERN U.S. FOR DJF AND JFM 2005 TO REFLECT WEAK EL NINO COMPOSITES... THE CFS MODEL FORECAST... AND INDICATIONS FROM CCA THAT THE GULF COAST WILL BE COOLER THAN POINTS NORTH. THESE TOOLS GAVE GENERALLY CONSISTENT INDICATIONS THAT MOST OF TEXAS WOULD REMAIN RELATIVELY COLD FOR OND 2004 THROUGH MAM 2005. FOR AMJ 2005 AND BEYOND THE TEMPERATURE FORECAST MAINLY REFLECTS TRENDS TOWARD WARMER THAN NORMAL TEMPERATURES IN MUCH OF THE WEST AND ALASKA... EXTENDING ACROSS THE SOUTHERN U.S. IN THE SUMMER MONTHS. THIS SIGNAL SHRINKS IN LATE SUMMER AND RETREATS TO THE SOUTHWESTERN U.S. AND SOUTHERN FLORIDA BY FALL 2005. HINTS FOR A DEVELOPING TREND FOR BELOW NORMAL TEMPERATURES IN VARIOUS PARTS OF THE NORTH-CENTRAL U.S. FROM MAM THROUGH MJJ 2005 WERE FOLLOWED. . . . . . . . . PRECIPITATION: ABOVE MEDIAN PRECIPITATION OVER FLORIDA FOR OND 2004 IS DUE TO TRENDS IN AND THE POSSIBILITY OF A CONTINUED ACTIVE ATLANTIC HURRICANE SEASON. THE IRI MULTI MODEL ENSEMBLE AND THE CDC NUMERICAL MODEL INTERPRETATION SYSTEM SUGGESTS ABOVE MEDIAN PRECIPITATION FOR THE ALASKAN PANHANDLE FOR OND 2004. FOR LEADS FROM OND THROUGH JFM THERE ARE ELEVATED CHANCES OF A WARM ENSO-LIKE PRECIPITATION ANOMALY PATTERN... ALTHOUGH ENSO IMPACTS ARE NOT ASSURED SO THE FINAL FORECAST HAS MUCH LOWER PROBABILITIES THAN WOULD BE EXPECTED FOR A STRONGER EL NINO. THE LOW RELIABILITY OF THE SIGNAL IS ALSO SUGGESTED BY A LACK OF CONSENSUS AMONG TOOLS... WITH THE CFS MODEL NOT SHOWING MUCH ABOVE MEDIAN PRECIPITATION IN THE SOUTHERN PART OF THE COUNTRY UNTIL FMA AND MAM 2005. THE IRI MULTI MODEL ENSEMBLE SHOWS ITS STRONGEST SIGNAL FOR WETNESS IN CALIFORNIA FOR DJF AND JFM 2005... WHILE OTHER MODELS KEEP THAT AREA DRY AND INDICATE ABOVE MEDIAN PRECIPITATION ONLY IN TEXAS. SINCE THIS WILL MOST LIKELY BE AT LEAST A WEAK WARM EVENT... THESE SLIGHT INDICATIONS FROM VARIOUS TOOLS WERE COMBINED TO FORM A COHERANT PATTERN SIMILAR TO A WARM ENSO EVENT COMPOSITE FOR THE WINTER AND SPRING. MOST OF THE STATISTICAL AND SOME OF THE DYNAMICAL MODELS INDICATE BELOW MEDIAN PRECIPITAION IN MONTANA. CCA AND SMLR FORECAST INDICATE ABOVE MEDIAN PRECIPITATION IN FLORIDA. THE CFS SHOWS DRY CONDITIONS IN THE OHIO VALLEY BY LATE WINTER AND SPRING 2005. THE MOST PROBLEMATIC AREA IS IN THE SOUTHWESTERN U.S. AND SOUTHERN CALIFORNIA. WHILE THE CHANCES OF ABOVE MEDIAN PRECIPITATION IN THIS AREA INCREASES SLIGHTLY FOR WEAK EL NINOS... THE CHANCE FOR DRY CONDITIONS DO NOT SUBSTANTIALLY DECREASE FROM WHAT MIGHT BE EXPECTED IN NEUTRAL ENSO YEARS UNLESS THE EL NINO BECOMES FAIRLY STRONG. WITH ABOVE NORMAL SSTS CLEARLY IN STORE FOR THE ENSO-SENSITIVE REGIONS OF THE CENTRAL PACIFIC... THE ODDS OF ABOVE MEDIAN PRECIPITATION IN THE SOUTHWEST ARE HIGHER THAN USUAL... BUT THIS IS DUE TO DECREASING THE ODDS OF NEAR MEDIAN AMOUNTS RATHER THAN LOWERING THE CHANCES OF BELOW MEDIAN AS WOULD USUALLY BE THE CASE. AFTER THE EL NINO RELATED SIGNALS DIE AWAY IN THE SPRING EC IS INDICATED DUE TO LACK OF ANY SIGNIFICANT SIGNALS EXCEPT FOR TREND RELATED INDICATIONS FOR BELOW MEDIAN PRECIPITATION IN THE GREAT BASIN AND PORTIONS OF THE SOUTHWEST IN SUMMER...AND ABOVE MEDIAN PRECIPITATION IN SOUTHERN FLORIDA FROM JAS THROUGH SON 2005 AND IN EASTERN TEXAS FOR OND 2005. NOTE - AREAS OF UNCERTAINTY THAT FORMERLY WERE LABELED CL (CLIMATOLOGICAL PROBABILITIES) ARE NOW LABELED EC (EQUAL CHANCES). . . . . . . . . FORECASTER: A. J. WAGNER 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. 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. 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 OCTOBER 21 2004. 1971-2000 BASE PERIOD MEANS WERE IMPLEMENTED EFFECTIVE WITH THE MAY 17 2001 FORECAST RELEASE. $$