PROGNOSTIC DISCUSSION FOR LONG-LEAD SEASONAL OUTLOOKS NWS CLIMATE PREDICTION CENTER CAMP SPRINGS MD 830 AM EDT THU JULY 15 2004 . . . . . . . . SUMMARY OF THE OUTLOOK FOR NON-TECHNICAL USERS THE SEASONAL OUTLOOK REFLECTS PRIMARILY THE PRESENCE OF LONG TERM TRENDS ON U.S. TEMPERATURE AND PRECIPITATION...STATISTICAL FORECAST TOOLS...WITH INPUT FROM NUMERICAL MODELS DURING THE FIRST SEVERAL SEASONS...ALL WITHIN THE CONTEXT OF THE LIKELY CONTINUATION OF ENSO-NEUTRAL CONDITIONS IN THE TROPICAL PACIFIC DURING THE NEXT SEVERAL MONTHS. SSTS IN THE TROPICAL PACIFIC ARE BELOW THE THRESHOLD REQUIRED TO PRODUCE SIGNIFICANT ENSO IMPACTS ON THE U.S. CLIMATE. A MAJORITY OF MODELS FAVORS POSITIVE SST ANOMALIES IN THE NINO 3.4 REGION BY THE UPCOMING COLD SEASON...BUT THE MAGNITUDE OF THE ANOMALIES ARE NOT ENOUGH TO SATISFY THE CRITERIA FOR AN EL NINO IN MANY CASES AND EVEN THE MODELS WITH THE LARGEST ANOMALIES ARE NOT FORECASTING A STRONG EL NINO. HOWEVER JUST IN THE LAST WEEK THE ANOMALIES NEAR AND EAST OF THE DATELINE HAVE RISEN SHARPLY. THIS CHANGE - IF SUSTAINED - WILL BE REFLECTED IN FORECASTS MADE NEXT MONTH. THE FORECAST FOR ASO 2004 FAVORs ABOVE NORMAL TEMPERATURES OVER MUCH OF THE WEST AND SOUTHWEST. SOME COOLER THAN NORMAL TEMPERATURES ARE EXPECTED FOR PORTIONS OF THE NORTH-CENTRAL STATES. A REGION OF ABNORMAL DRYNESS IS LIKELY DURING ASO OVER THE WESTERN U.S. MAINLY FROM THE IDAHO NEVADA BORDER SOUTHWARD. SOUTH FLORIDA IS EXPECTED TO BE ABOVE NORMAL FOR TEMPERATURE AND ABOVE MEDIAN FOR PRECIPITATION DUE TO LONG TERM TRENDS AND IN THE CASE OF PRECIPITATION SUPPORTED ALSO DUE AN EXPECTED ACTIVE HURRICANE SEASON. IN ALASKA EQUAL CHANCES ARE GIVEN FOR THE THREE POSSIBLE CATEGORIES FOR BOTH PRECIPITATION AND TEMPERATURE (ABOVE - NEAR MEDIAN OR NEAR NORMAL - BELOW) UNTIL FMA 2005. THE AUTUMN SEASONS OF SON AND OND HAVE THE WEAKEST SIGNALS FOR TEMPERATURE OF THE ENTIRE YEAR OVER THE CONUS AND THE TREND SIGNAL FOR ABOVE NORMAL TEMPERATURES CONTINUES FOR PORTIONS OF THE SOUTHWEST. THERE IS AN INDICATION FOR ABOVE MEDIAN PRECIPITATION OVER PARTS OF THE SOUTH-CENTRAL STATES IN OND THROUGH DJF AS WELL AS AN INDICATION FOR BELOW MEDIAN PRECIPITATION FOR SMALL PORTIONS OF THE CENTER OF THE NATION IN OND AND NDJ. DURING THE COMING WINTER AND FOLLOWING SPRING LONG-TERM TRENDS FAVOR ABOVE NORMAL TEMPERATURES CENTERED OVER THE MIDWEST DURING THE WINTER... REACHING MAXIMUM AREAL COVERAGE OF MUCH OF THE COUNTRY DURING JFM AND SETTLING INTO THE WEST AND SOUTHWEST FOR THE REMAINING SEASONS. MOST OF THESE SEASONS HAVE LIMITED RELIABLE SIGNALS FOR PRECIPITATION. . . . . . . . . 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 AVERAGE OF SST ANOMALIES SHOWS THAT SEA SURFACE TEMPERATURES ARE MORE THAN 1 C ABOVE NORMAL ALONG THE EQUATOR FROM 175E TO 145W. THERE IS AN AREA OF NEGATIVE SST ANOMALIES EXTENDING FROM THE COAST OF PERU WEST TO ABOUT 125W. RECENT 5-DAY MEAN TOGA-TAO DEPTH-LONGITUDE CROSS-SECTIONS SHOW ABNORMALLY WARM WATER...WITH ANOMALIES OF UP TO 3 C... BETWEEN THE SURFACE AND ABOUT 100 M DEPTH JUST EAST OF THE DATE LINE. THIS NEW SUPPLY OF SUB SURFACE WARM WATER IS THE RESULT OF A BURST OF WESTERLY WINDS THAT OCCURRRED OVER THE FAR WESTERN TROPICAL PACIFIC DURING JUNE. . . . . . . . . PROGNOSTIC DISCUSSION OF SST FORECASTS FORECASTS FROM MULTIPLE MODELS DISPLAYED BY IRI GIVE A RANGE OF POSSIBLE FUTURE SST ANOMALIES IN NINO 3.4 OF -0.2 TO +1.0 C THROUGH SON WITH A FAIRLY EVEN SPLIT BETWEEN THOSE WHICH ARE BELOW AND ABOVE 0.5 C...THE BOUNDARY BETWEEN NEUTRAL AND A WEAK WARM EVENT...BY EARLY WINTER...WITH SIGNIFICANT UNCERTAINTY. TO SEE THESE FORECASTS GO TO ITEM 30 (IRI) ON http:// www.cpc.ncep.noaa.gov/products/predictions/90day/tools/briefing/index.pri.html A CONSOLIDATION FORECAST OF IN-HOUSE TOOLS INDICATES THAT NINO 3.4 SST ANOMALIES WILL RISE FROM ITS CURRENT SLIGHTLY POSITIVE VALUES TO ABOUT +0.8C... ABOVE THE +0.5 C THRESHOLD FROM SON FOREWARD. THE TOOLS ARE IN REMARKABLE AGREEMENT. THE PROBABILITY SPREAD FOR COLD - NEUTRAL - OR WARM ENSO CONDITIONS INCREASES WITH THE GREATEST LIKELIHOOD SHIFTING FROM NEAR NORMAL IN ASO TO ABOUT EQUAL CHANCES FOR NEUTRAL OR WARM ENSO CONDITIONS BY FALL AND A SHIFT TO BETTER CHANCES OF WARM BY LATE FALL. THERE IS LITTLE EXPECTATION FOR A COLD EVENT TO DEVELOP. SINCE WEAK WARM EVENTS DO NOT EXERT STRONG FORCING ON THE ATMOSPHERE...SHOULD ONE DEVELOP...WE EXPECT THAT TRANSIENT ATMOSPHERIC CIRCULATION PATTERNS WILL CONTINUE TO BE FORCED PRIMARILY BY INTRA-SEASONALLY VARYING PHASES OF THE MJO...AND THE HIGHER LATITUDE PATTERNS WILL BE DETERMINED BY VARYING PHASES OF THE LEADING MODES SUCH AS PNA AND AO AND NAO THAT ARE NOT CURRENTLY PREDICTABLE AT SEASONAL RANGES. PROGNOSTIC TOOLS USED FOR U.S. TEMPERATURE AND PRECIPITATION OUTLOOK THE PRIMARY TOOLS USED WERE OCN...CCA...AND SMLR AUGMENTED BY ENSEMBLE CCA AND TREND ADJUSTED ENSO COMPOSITES. CONSULTED WERE TWO-TIER FORECASTS FROM SIX MODELS PROVIDED BY CDC - DYNAMICAL MULTI-MODEL ENSEMBLES FROM IRI AND DYNAMICAL MODEL FORECASTS FROM NCEPS ENVIRONMENTAL MODELING CENTER. SPECIAL ATTENTION WAS GIVEN TO A NEW 1-TIER NCEP DYNAMICAL MODEL CALLED CFS WHICH WILL BECOME OPERATIONAL AUGUST 24 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. THE CONSTRUCTED ANALOG TECHNIQUE USING SOIL MOISTURE (CAS) WAS CONSIDERED BUT FOR THE FIRST LEAD ONLY. . . . . . . . . PROGNOSTIC DISCUSSION OF OUTLOOKS - ASO 2004 TO ASO 2005 TEMPERATURE: FOR ASO 2004 CCA AND OCN HAVE INDICATIONS OF ABOVE NORMAL TEMPERATURES FOR THE PACIFIC NORTHWEST AND STRONGER INDICATIONS FOR MUCH OF THE SOUTHWESTERN U.S. AND SOUTH FLORIDA. BELOW NORMAL WAS PREDICTED FOR PORTIONS OF THE NORTH-CENTRAL STATES IN ASO BECAUSE OF A STRONG SIGNAL FOR BELOW NORMAL TEMPERATURES IN CAS DUE TO RECENT HEAVY PRECIPITATION. THE TREND SIGNAL IS WEAK IN ALASKA FOR ASO 2004 THROUGH JFM 2005. BY SON THE TREND FOR ABNORMAL WARMTH RETREATS TO A SMALL SECTION OF THE INTERIOR SOUTHWEST CENTERED ON ARIZONA WHILE SOUTHERN FLORIDA REMAINS IN THE ABOVE NORMAL CATEGORY. THE CCA-OCN SIGNAL FADES TO EC ALMOST EVERYWHERE BY OND WHEN THE SKILL OF CCA AND OCN ARE AT THEIR ANNUAL MINIMUM. THE SIGNAL BEGINS TO REBOUND IN NDJ IN THE CORE OF THE SOUTHWEST...AND BY DJF THIS REGION GETS COMPANY FROM THE EASTERN GREAT PLAINS TO PARTS OF THE NORTHEAST. THE CCA-OCN SIGNAL PEAKS IN JFM 2005 WHEN MORE OF THE NATION IS LIKELY TO HAVE ABOVE NORMAL TEMPERATURES THAN IN ANY OTHER SEASON. CCA-OCN INDICATES ABNORMAL WARMTH MAINLY IN THE WEST FROM FMA THROUGH AMJ. BY THE FINAL THREE LEADS...JJA - ASO 2005... THE OCN TOOL AGAIN INDICATES ENHANCED LIKELIHOOD FOR ABNORMAL WARMTH FOR PARTS OF THE SOUTHWEST AND SOUTHEAST...AND DURING FMA - ASO IN PARTS OF ALASKA AS WELL. . . . . . . . . PRECIPITATION: THERE IS A LIKELIHOOD OF BELOW MEDIAN PRECIPITATION FOR ASO 2004 FROM OCN AND CCA FOR VARIOUS PARTS OF THE GREAT BASIN SOUTHWARD. AN ENHANCED LIKELIHOOD OF ABOVE MEDIAN PRECIPITATION IS EXPECTED IN PARTS OF THE NORTH - CENTRAL U.S. DUE TO SOIL MOISTURE EFFECTS. ABOVE MEDIAN PRECIPITATION OVER COASTAL SE U.S. IS DUE TO TRENDS IN FLORIDA AND THE POSSIBILITY OF TROPICAL SYSTEMS GIVEN THAT NOAA EXPECTS AN ABOVE NORMAL ATLANTIC HURRICANE SEASON. FOR MOST FOLLOWING SEASONS EC IS INDICATED DUE TO LACK OF ANY SIGNIFICANT SIGNALS. EXCEPTIONS ARE ABOVE MEDIAN PRECIPITATION IN OK AND TX AND FL FOR SEVERAL SEASONS IN WINTER. INDICATIONS FOR BELOW MEDIAN PRECIPITATION CAN BE FOUND IN THE CENTER OF THE COUNTRY FROM OND ONWARD MOVING NORTHWESTWARD INTO MONTANA BY DJF. ALTHOUGH MOST OF THESE SIGNALS ARE DUE TO TREND THE POSSIBILITY OF A WEAK EL NINO INCREASES OUR CONFIDENCE. AFTER SEVERAL COMPLETE EC MAPS DURING SUMMER THE FAMILIAR TRENDS SIGNALS RETURN IN THE JAS and ASO 2005. NOTE - AREAS OF UNCERTAINTY THAT FORMERLY WERE LABELED CL (CLIMATOLOGICAL PROBABILITIES) ARE NOW LABELED EC (EQUAL CHANCES). . . . . . . . . FORECASTER: H. VAN DEN DOOL 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 AUGUST 19 2004. 1971-2000 BASE PERIOD MEANS WERE IMPLEMENTED EFFECTIVE WITH THE MAY 17 2001 FORECAST RELEASE. $$