PROGNOSTIC DISCUSSION FOR LONG-LEAD SEASONAL OUTLOOKS NWS CLIMATE PREDICTION CENTER CAMP SPRINGS MD 830 AM EDT THU AUGUST 19 2004 . . . . . . . . SUMMARY OF THE OUTLOOK FOR NON-TECHNICAL USERS CURRENT OBSERVATIONS AND A MAJORITY OF SEA SURFACE TEMPERATURE (SST) PREDICTION TOOLS INDICATE AN ENHANCED LIKELIHOOD OF WEAK EL NINO CONDITIONS FROM THIS FALL THROUGH AT LEAST EARLY 2005. THE CONSENSUS AMONG STATISTICAL AND DYNAMICAL MODEL PREDICTIONS INDICATES THAT 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 INCREASE FROM CURRENT LEVELS OF JUST UNDER +.6 DEG C IN JJA TO PEAK VALUES OF BETWEEN +.6 AND +1.0 DEGREES C IN NDJ 2004/2005. UNCERTAINTIES ABOUT THE STRENGTH AND LOCATION OF THE ANTICIPATED ABNORMALLY WARM TROPICAL PACIFIC SSTS COME INTO PLAY FOR THIS FORECAST. TROPICAL PACIFIC SSTS HAVE BEEN CHARACTERIZED BY A LARGE AMOUNT OF WITHIN- SEASON (INTRA-SEASONAL OR 30-60 DAY TIME SCALE) VARIABILITY THIS SUMMER... LARGELY DUE TO THE INFLUENCE OF MADDEN-JULIAN OSCILLATIONS (MJO)... AN MJO EPISODE OFTEN APPEARS TO BEGIN WHEN A LARGE REGION OF ENHANCED DEEP THUNDERSTORM ACTIVITY MOVES EASTWARD FROM THE INDIAN OCEAN INTO INDONESIA AND THE WESTERN TROPICAL PACIFIC. THE EXTRA CLOUDINESS IS FREQUENTLY ACCOMPANIED BY ABNORMALLY WEAK EASTERLY...OR EVEN ACTUAL WESTERLY...SURFACE WINDS. THIS WIND FIELD OFTEN AFFECTS THE OCEAN BENEATH IT AND FREQUENTLY GIVES RISE TO OCEANIC KELVIN WAVES (OKW) BELOW THE OCEAN SURFACE. OKW PROPAGATE EASTWARD ALONG THE EQUATOR CARRYING ABNORMALLY WARM SUB-SURFACE WATER TOWARD...AND EVENTUALLY TO...THE SOUTH AMERICAN COAST. ONE SUCH OKW IS NOW REACHING THE SOUTH AMERICAN COAST. AS THE ABNORMALLY WARM WATER IS FORCED TO THE SURFACE THE WATER THERE IS EXPECTED TO WARM BACK TO NORMAL. MEANWHILE...A WESTERLY WIND BURST IS CURRENTLY IN PROGRESS IN THE TROPICS BETWEEN 120E AND 150E...ASSOCIATED WITH YET ANOTHER EMERGING MJO. CPC IS CLOSELY MONITORING THE INFLUENCE OF THIS LATEST EVENT ON TROPICAL PACIFIC SSTS. THE PATTERN AND SIZE OF SST ANOMALIES IN THE TROPICAL PACIFIC STRONGLY INFLUENCES THE MIDDLE LATITUDE IMPACTS OF EL NINO. . . . . . . . . EASTERN PACIFIC...OR CLASSICAL... EL NINOS...LIKE THOSE IN 1982-83 AND 1997-98 HAVE A PATTERN OF ABNORMALLY WARM SST WHICH EXTENDS 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 IN THE CENTRAL TROPICAL PACIFIC. THIS YEARS EVENT IS LIKELY TO HAVE WEAK WARM ANOMALIES WHICH...AS OF THIS DATE... SEEM LIKELY TO BE LIMITED TO THE CENTRAL TROPICAL PACIFIC. UNCERTAINTY ABOUT THESE TWO FACTORS...THE ULTIMATE MAGNITUDE OF THE POSITIVE SST ANOMALIES AND THE QUESTION OF CENTRAL VERSUS EASTERN PACIFIC EVENT-TYPE ARE THE ONES WHICH MOST SHAPE OUR FORECAST. DYNAMICAL CLIMATE MODELS INDICATE A MINIMAL ATMOSPHERIC RESPONSE TO THE ANTICIPATED WARM SSTS IN THE CENTRAL EQUATORIAL PACIFIC... AS DOES AN ANALYSIS OF THE U.S. CLIMATE ANOMALIES ASSOCIATED WITH PAST WEAK EL NINOS. STILL... SOME EL NINO RELATED INFLUENCE ON U.S. CLIMATE CANNOT BE RULED OUT FOR THIS 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 SON 2004 IS BASED ON INDICATIONS FROM WARMING TRENDS IN THE SOUTHWESTERN U.S... WITH ABOVE NORMAL TEMPERATURES ANTICIPATED ALONG THE NORTHWEST U.S. COAST AND IN COASTAL ALASKA PRIMARILY DUE TO ABNORMALLY WARM SSTS IN THE 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 FORECASTS FROM OTHER TOOLS. TEMPERATURES IN THE SOUTHEASTERN U.S. ARE TYPICALLY COOLER FOR WEAK EL NINOS BASED ON WARM CENTRAL EQUATORIAL PACIFIC SSTS THAN FOR THEIR MODERATE AND STRONGER COUNTERPARTS WHOSE WARM SST ANOMALIES EXTEND TO THE COAST OF SOUTH AMERICA. THUS FORECAST TEMPERATURES IN THE EASTERN U.S. HAVE BEEN REVISED DOWNWARD FROM THOSE INDICATED ON THE OUTLOOK ISSUED LAST MONTH AND INCLUDE SOME INDICATIONS OF BELOW NORMAL TEMPERATURES OVER THE SOUTHEASTERN U.S. IN THE WINTER. TEMPERATURES OVER THE NORTHWESTERN U.S. AND ALASKA HAVE BEEN REVISED TO REFLECT INCREASED CHANCES OF WARMER THAN NORMAL CONDITIONS IN EL NINO YEARS. BOTH OF THESE CHANGES ARE SUPPORTED BY DYNAMICAL MODEL FORECASTS. 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 MID SUMMER... WITH THE WARMER THAN NORMAL TEMPERATURES EXTENDING INTO THE FALL OVER SOUTH FLORIDA AND THE SOUTHWESTERN U.S. . . . . . . . . PRECIPITATION FOR SON 2004 REFLECTS LONG TERM TRENDS FOR ABOVE MEDIAN RAINFALL IN SOUTHERN FLORIDA. SOME DYNAMICAL MODELS PREDICT ABOVE-MEDIAN PRECIPITATION FOR THE ALASKAN PANHANDLE IN THE FALL. THE WINTER-TIME PRECIPITATION PATTERN OF GENERALLY WET CONDITIONS ALONG THE SOUTHERN U.S. AND DRY CONDITIONS IN THE NORTHERN U.S. AND THE TENNESSEE VALLEY REFLECTS CLASSICAL EL NINO CONDITIONS... ALTHOUGH THE WITH MUCH LESS CONFIDENCE THAN WOULD BE GIVEN IN A STRONGER EVENT. THE INTRODUCTION... IN THIS MONTHS FORECASTS... OF EL NINO IMPACTS ON PRECIPITATION IS A SUBSTANTIAL REVISION FROM LAST MONTHS OUTLOOK... HOWEVER IT IS IMPORTANT TO NOTE THAT THE ODDS DO NOT REFLECT THE VERY HIGH LEVEL OF CONFIDENCE WE WOULD ASSUME IN A MODERATE OR STRONG 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 TEXAS WHERE TRENDS ARE IN THEIR FAVOR. DRY CONDITIONS ALONG THE NORTHERN STATES ARE FROM ENSO COMPOSITES... WHICH ALSO ARE ONLY SLIGHTLY FAVORED IN WEAK ENSO EVENTS. THERE IS SOME 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 AMJ 2005 AND BEYOND THE OUTLOOK REFLECTS PRECIPITATION TRENDS...WHICH ARE GENERALLY MODEST IN SIZE... AND ONLY IN LIMITED PORTIONS OF THE WEST... WHERE DRY CONDITIONS ARE INDICATED IN JAS AND ASO... AND ALSO TRENDS HINTING AT ABOVE MEDIAN PRECIPITATION IN FLORIDA FOR SEASONS JAS THROUGH SON 2005. . . . . . . . . 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 THE EQUATOR FROM 165E TO 120W. SSTS ALONG AND JUST SOUTH OF THE EQUATOR AVERAGE AROUND 1 DEGREE C BELOW NORMAL FROM THE SOUTH AMERICAN COAST TO AROUND 100W. SUB-SURFACE OCEAN TEMPERATURES ALONG THE EQUATOR ARE SUBSTANTIALLY ABOVE NORMAL OVER THE EAST-CENTRAL PACIFIC FROM THE SURFACE TO OVER 200 METERS DEPTH... WITH MAXIMUM ANOMALIES OF OVER +6 DEGREES C AT 100 METERS DEPTH AROUND 140W. 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 RISE FROM THE JULY AVERAGE OF ABOUT +.6 C TO JUST UNDER +1 C BY EARLY FALL AND REMAIN STEADY FOR MOST OF THE WINTER SEASON BEFORE SLOWLY DECREASING IN 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. AND +2. DEGREES C... WITH THE MAJORITY BETWEEN +.4 C AND +1.2 C. MOST MODELS PREDICT THE POSITIVE SST ANOMALIES IN DJF 2004/05 TO BE RESTRICTED TO A RELATIVE 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 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 ENVIRONMENTAL MODELING CENTER PROVIDED INPUT THROUGH DJF 2004/05. THE NEW CFS MODEL WHICH WILL BECOME OPERATIONAL ON AUGUST 24 2004 PROVIDES FORECASTS THROUGH FMA 2005. CCA... OCN AND SMLR GUIDANCE WERE CONSULTED FOR ALL LEAD TIMES. 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 - SON 2004 TO SON 2005 TEMPERATURE: FOR SON 2004 THE IRI MULTI MODEL ENSEMBLE PREDICTION SUGGESTS ABOVE NORMAL TEMPERATURES FOR MUCH OF THE WESTERN U.S. AND ALASKA... BUT WITH CONTRADICTIONS FROM THE CFS MODEL THE ABOVE NORMAL TEMPERATURES WERE CONFINED MOSTLY TO COASTAL REGIONS WHERE ADJACENT SSTS ARE SUBSTANTIALLY ABOVE NORMAL. OCN INDICATES ABOVE NORMAL TEMPERATURES OVER THE SOUTHWESTERN U.S. FOR SON 2004. AS THE SEASONS PROGRESS TOWARDS WINTER... ABOVE NORMAL TEMPERATURES ARE PREDICTED TO DEVELOP OVER NORTHWESTERN PORTIONS OF THE U.S. AND SPREAD EASTWARD. THIS PATTERN AGREES WITH CFS MODEL AND ENSO COMPOSITES. THE CFS MODEL PREDICTS NOTABLY COLD TEMPERATURES IN THE EASTERN U.S. THROUGH FMA 2005. THESE ARE SUPPORTED BY WEAK EL NINO COMPOSITES AND FORM THE BASIS OF A SUBSTANTIAL REVISION OVER THE EASTERN U.S. FROM LAST MONTHS OUTLOOK. 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 MOST OF THE EASTERN 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. FOR MAM 2005 AND BEYOND THE TEMPERATURE FORECAST MAINLY REFLECTS TRENDS TOWARD WARMER THAN NORMAL TEMPERATURES IN MUCH OF THE WEST AND ALASKA... EXTENDING TO 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. . . . . . . . . PRECIPITATION: ABOVE MEDIAN PRECIPITATION OVER FLORIDA FOR SON 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 THROUGH 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. THE CFS MODEL DEVELOPS A PATTERN SIMILAR TO A WARM EVENT COMPOSITE BY DJF... ALTHOUGH THE IRI MULTI MODEL ENSEMBLE DOES NOT. SINCE THIS WILL ALMOST CERTIANLY BE AT LEAST A WEAK WARM EVENT... THE SLIGHT INDICATIONS FROM VARIOUS TOOLS WERE COMBINED TO FORM A COHERANT PATTERN SIMILAR TO A WARM ENSO EVENT COMPOSITE FOR THE WINTER AND SPRING. THE CFS MODEL... CCA... OCN... ALL INDICATE ABOVE MEDIAN PRECIPITATION IN TEXAS AND BELOW MEDIAN PRECIPITAION IN MONTANA. CCA AND SMLR FORECAST INDICATE ABOVE MEDIAN PRECIPITATION IN FLORIDA. THE CFS SHOWS DRY CONDITIONS IN THE OHIO VALLEY AND THE PACIFIC NORTHWEST. 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 UNTIL THE EL NINO BECOMES MODERATE OR STRONG. WITH WARM 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. NOTE - AREAS OF UNCERTAINTY THAT FORMERLY WERE LABELED CL (CLIMATOLOGICAL PROBABILITIES) ARE NOW LABELED EC (EQUAL CHANCES). . . . . . . . . FORECASTER: D. UNGER 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 SEPTEMBER 16 2004. 1971-2000 BASE PERIOD MEANS WERE IMPLEMENTED EFFECTIVE WITH THE MAY 17 2001 FORECAST RELEASE. $$