PROGNOSTIC DISCUSSION FOR LONG-LEAD SEASONAL OUTLOOKS NWS CLIMATE PREDICTION CENTER CAMP SPRINGS MD 300 PM EDT THU MAY 15 2003 . . . . . . . . SUMMARY OF THE OUTLOOK FOR NON-TECHNICAL USERS THE SEASONAL OUTLOOK REFLECTS THE PRESENCE OF LONG TERM TRENDS IN U.S. TEMPERATURE AND PRECIPITATION...STATISTICAL FORECAST TOOLS ...WITH SOME INPUT FROM NUMERICAL MODELS DURING THE FIRST SEVERAL SEASONS AND - FINALLY - THE GROWING LIKELIHOOD A LA NINA WILL DEVELOP BY OR BEFORE THE JULY-AUGUST- SEPTEMBER SEASON. SOIL MOISTURE INDICATIONS ARE NOT HEAVILY RELIED UPON SINCE SOIL MOISTURE ANOMALIES ARE UNUSUALLY WEAK IN THE WEST THIS YEAR AND HAVE NO KNOWN SKILL IN THE EAST WHERE WET SOIL MOISTURE ANOMALIES ARE WIDE SPREAD. THE RAPID TRANSITION BETWEEN EL NINO AND LA NINA INCREASES THE ALREADY SEASONALLY HIGH UNCERTAINTY ASSOCIATED WITH FORECASTS AT THIS TIME OF YEAR. THEREFORE BOTH PROBABILITIES AND AREA COVERED BY NON-EC PROBABILITIES WILL BE REDUCED IN THIS SET OF FORECASTS - WHILE THE EVOLUTION OF THE FORECASTS REFLECTS A TRANSITION TO LA NINA CONDITIONS THIS FALL AND WINTER. LA NINA CONSIDERATIONS CEASE AFTER JFM. THE OUTLOOK FOR JUNE-AUGUST 2003 CALLS FOR ABOVE NORMAL TEMPERATURES OVER THE SOUTHWEST - SOUTHERN TEXAS AND SECTIONS OF THE SOUTHEAST. PRECIPITATION IS CURRENTLY UNPREDICTABLE FOR JJA AND EQUAL CHANCES ARE PREDICTED OVER THE CONTERMINOUS US AND ALASKA FOR JJA. FORECASTS FOR THE REMAINDER OF THE SUMMER THROUGH JFM REFLECT AN INCREASING SHIFT TO LA NINA IMPACTS. AFTER JFM - TREND-ADJUSTED ENSO-NEUTRAL COMPOSITES (COMPOSITES CONDITIONAL ON TROPICAL PACIFIC SSTS FOR SEASONS DURING WHICH NEITHER PHASE OF EL NINO OCCURRED) ARE RELIED UPON ALONG WITH CCA. . . . . . . . . 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 EQUATORIAL PACIFIC SEA SURFACE TEMPERATURES WHICH - IN EARLY APRIL - WERE BETWEEN ONE-HALF AND ONE DEGREE C OR MORE ABOVE NORMAL OVER THE EQUATORIAL PACIFIC NEAR THE DATE LINE - DECLINED TO NO MORE THAN ONE-HALF DEGREE ABOVE NORMAL AT 180 AND WERE ONE-HALF TO 2 DEGREES BELOW NORMAL EAST OF 160W WITH COLD ANOMALIES INCREASING TO THE EAST. MODEL SST FORECASTS OF SEASONAL AVERAGE SSTS IN THE NINO 3.4 REGION - PREPARED AT THE BEGINNING OF MAY INDICATE A NEAR- EVEN SPLIT AMONG MODELS BETWEEN WARM AND COLD CONDITIONS. STATISTICAL FORECASTS WERE AS VARIED AS THE DYNAMICAL MODELS. CONSTRUCTED ANALOGS PREDICTS A COLD EVENT - WHILE THE MARKOV - CCA AND COUPLED MODELS PREDICT A MODEST WARM EVENT. THE OBSERVATIONS INDICATE THE MODELS HAVE NOT BEEN ABLE TO KEEP UP WITH NATURE. THE CURRENT ABNORMALLY COLD SSTS EAST OF 160w AND AN EXCESS OF ABNORMALLY COLD WATER BENEATH THE SURFACE INDICATE A COLD EVENT IS MUCH MORE LIKELY NOW - IN MID-MAY - THAN IT WAS IN LATE APRIL OR EVEN EARLY MAY. LA NINA CONDITIONS SEEM LIKELY TO DEVELOP BEFORE THE JAS SEASON THOUGH THE FULL ATMOSPHERIC RESPONSE IS LIKELY TO TAKE LONGER TO DEVELOP. CURRENT ATMOSPHERIC AND OCEANIC CONDITIONS WARM EPISODE CONDITIONS DISSIPATED IN THE TROPICAL PACIFIC DURING MARCH AND APRIL 2003. THIS CHANGE WAS CHARACTERIZED BY CONTINUED DECLINE IN SST ANOMALIES IN THE CENTER AND EASTERN EQUATORIAL PACIFIC AND THE DEVELOPMENT OF DRIER-THAN-AVERAGE CONDITIONS OVER THE CENTRAL EQUATORIAL PACIFIC. SIGNIFICANT DECREASES IN SST ANOMALIES OCCURED IN ALL OF THE NINO REGIONS DURING APRIL AND EARLY MAY. BY MID-MAY EQUATORIAL SSTS WERE NEAR OR BELOW NORMAL BETWEEN 165W AND THE SOUTH AMERICAN COAST - WITH ONLY A SMALL AREA OF POSITIVE SST ANOMALIES WEST OF THE DATE LINE BETWEEN 155E AND 175E. EASTERLY WINDS HAVE BEEN STRONGER THAN NORMAL OVER THE CENTRAL AND WEST-CENTRAL EQUATORIAL PACIFIC DURING MARCH AND APRIL. ALSO - THE SOI HAS CHANGED SIGN FROM NEGATIVE TO POSITIVE. THE DEPTH OF THE THERMOCLINE IN THE CENTRAL AND EASTERN TROPICAL PACIFIC OCEAN HAS ALSO DECREASED DURING THIS PERIOD. BY LATE APRIL NEGATIVE SURFACE TEMPERATURE ANOMALIES OF FROM -1 TO -3 DEGREES C HAD DEVELOPED BETWEEN 140W AND THE COAST OF SOUTH AMERICA. . . . . . . . . PROGNOSTIC DISCUSSION OF SST FORECASTS A SET OF 15 DYNAMICAL COUPLED OCEAN-ATMOSPHERE MODELS AND STATISTICAL MODEL SST FOR NINO 3.4 FORECASTS MADE AVAILABLE BY THE INTERNATIONAL INSTITUTE FOR CLIMATE PREDICTION (IRI) ARE MORE OR LESS EVENLY SPLIT BETWEEN WEAK WARM AND WEAK COLD EVENT CONDITIONS AFTER SPRING 2003. AMONG THOSE PREDICTING WEAK WARM EVENT CONDITIONS IN NINO 3.4 IS THE JMA WHICH PREDICTS NEARLY +1 C DEGREE ANOMALIES DURING THE SUMMER FOLLOWED BY GRADUALLY DECLINING ANOMALIES. CPCS CCA SST FORECAST IS NEARLY AS WARM. OTHERS PREDICTING A WEAK WARM EVENT ARE CPCS MARKOV - NLCCA - CSIRO - SCRIPPS - AND NCEP. FSU AND POAMA PREDICT NEAR-NORMAL NINO 3.4 SST ANOMALIES. FOREMOST AMONG MODELS PREDICTING A COLD EVENT BEYOND MAY 2003 IS NASAS NSIPP - WHICH PREDICTS ANOMALIES BELOW -1 DEGREE C BY AMJ AND -1.4 C BY JAS. MODELS PREDICTING MODEST LA NINA CONDITIONS INCLUDE ECMWF - CDC LINEAR INVERSE - CPC CA - LDEO - CLIPER AND KOREA. A GRAPH OF THESE FORECASTS MAY BE SEEN AT: http://www.cpc.ncep.noaa.gov/products/predictions/90day/tools/briefing/plume.gif A CONSOLIDATION FORECAST OF IN-HOUSE TOOLS SHOWS TEMPERATURE ANOMALIES IN THE NINO 3.4 SST REGION NEAR ZERO FOR NEXT WINTER AND SPRING 2004. WE REGARD THIS FORECAST AS TOO WARM AND CONCLUDE THAT LA NINA CONDITIONS ARE MORE LIKELY THAN THE CONSOLIDATION INDICATES. 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 WERE EXAMINED FOR THE PERIOD JJA 2003 - SON 2003. IN THE WARM SEASON WE ALSO PAY ATTENTION TO SOIL MOISTURE TOOL CAS - HOWEVER - INITIAL SOIL MOISTURE ANOMALIES ARE UNUSUALLY WEEK THIS SPRING AND MAY NOT PLAY A SIGNIFICANT ROLE IN THE CLIMATE IN THE EARLY SUMMER. NEARLY ALL OF THE DYNAMICAL MODELS CONSULTED PREDICT UNUSUALLY COLD AND WET CONDITIONS FOR NORTHWESTERN NORTH AMERICA AND ABNORMAL WARMTH AND DRYNESS FOR SOUTHERN NORTH AMERICA. THERE IS A TENDENCY IN THESE DYNAMICAL MODELS TO PREDICT ENHANCED PRECIPITATION AND COOL TEMPERATURES IN NORTHWESTERN CONTINENTAL US AND EXTRA WETNESS OVER SOUTHERN FLORIDA. THE DYNAMICAL MODELS ALSO INDICATE PRIMARILY DRY CONDITIONS OVER MUCH OF THE CONTINENTAL US - ESPECIALLY THE GREAT PLAINS AND THE ROCKIES - DURING THE SUMMER. THE COLD SIGNAL OVER ALASKA INDICATED IN THESE MODELS DURING THE SUMMER OF 2003 TENDS TO BE COUNTER-ACTED BY THE TREND. . . . . . . . . PROGNOSTIC DISCUSSION OF OUTLOOKS - JJA 2003 TO JJA 2004 TEMPERATURE: THE TEMPERATURE FORECAST FOR JJA IS BASED UPON A TREND-ADJUSTED COMPOSITE OF 28 CASES FROM THE HISTORICAL RECORD WHICH WERE CHARACTERIZED BY COLD-ENSO TROPICAL PACIFC OCEAN SURFACE TEMPERATURES ALONG WITH INDICATIONS FROM CCA - OCN AND DYNAMICAL MODELS. LA NINA-RELATED IMPACTS ARE GENERALLY WEAK OVER THE CONTINENTAL US DURING JJA. TEMPERATURES ARE EXPECTED TO REMAIN SLIGHTLY ABOVE NORMAL IN WESTERN ALASKA DURING JJA. IN THE CONTINENTAL US THE TREND REQUIRES WARM ANOMALIES CENTERED OVER THE SOUTHWEST AND FLORIDA. THESE CONSIDERATIONS CONTINUE THROUGH SON - THOUGH ALASKA TEMPERATURES ARE CONSIDERED UNPREDICTABLE THROUGH MUCH OF THE WARM SEASON AFTER JJA. FROM OND THROUGH JFM TEMPERATURE FORECASTS ARE BASED PRIMARILY UPON COMPOSITES CONDITIONAL UPON THE PRESUMED EXISTENCE OF A WEAK TO MODERATE LA NINA ALONG WITH INDICATIONS FROM CCA AND TREND. PREDICTED COLD TEMPERATURES IN ALASKA ARE CONFINED TO THE INTERIOR - WHERE COLD TEMPERATURES WERE SEEN IN PRIOR LA NINAS. COLD TEMPERATURES ARE DIFFICULT TO PREDICT IN A REGION WHICH HAS SEEN WARM ANOMALIES FOR AN EXTENDED PERIOD - HOWEVER MODEL FORECASTS AND KNOWN ENSO RESPONSES APPEAR LIKELY TO OVERCOME THE RECENT TENDENCY TOWARD ABNORMAL WARMTH THERE. FORECASTS AFTER JFM ARE BASED ON TREND-ADJUSTED ENSO-NEUTRAL COMPOSITES AND CCA. . . . . . . . . PRECIPITATION: THERE IS A POSSIBILITY LA NINA CONDITIONS WILL COMMENCE AS EARLY AS THE JJA SEASON. LA NINA IS OFTEN - THOUGH NOT ALWAYS - ASSOCIATED WITH ENHANCED MONSOON CONDITIONS OVER THE SOUTHWESTERN US. HOWEVER - GIVEN THE ODDS OF A LA NINA ARE ONLY ABOUT 60 PERCENT - ENHANCED PRECIPITATION IS NOT EXPLICITLY PREDICTED IN ARIZONA AND NEW MEXICO FOR JAS OR ASO. SHOULD THE TREND TOWARD LA NINA CONTINUE THIS POSSIBILITY WILL BE REVISITED IN JUNE FOR THE NEXT FORECAST. ALSO - LA NINA CONDITIONS ARE HIGHLY LIKELY DURING THE PEAK OF THE TROPICAL STORM SEASON AND ARE KNOWN TO ENHANCE PRECIPITATION ALONG THE ATLANTIC AND GULF COASTS BY UP TO 15 PERCENT DURING THE FALL. THESE CONSIDERATIONS ARE CONSERVATIVELY REFLECTED IN OUR FORECASTS AND WILL BE UPGRADED IN NEXT MONTHS FORECAST SHOULD LA NINA DEVELOP AS EXPECTED. PRECIPITATION IS CONSIDERED TO BE UNPREDICTABLE DURING JJA 2003. DURING JAS THROUGH SON - TREND-ADJUSTED ENSO COMPOSITES AND DYNAMICAL MODELS ALL INDICATE ABOVE NORMAL PRECIPITATION IN FLORIDA. DRY REGIONS IN THE WESTERN US FROM JAS THROUGH OND ARE INDICATED BY TREND-ADJUSTED ENSO COMPOSITES - AS IS THE WET ANOMALY IN THE NORTHWEST US FROM OND THROUGH NDJ - THE WET ANOMALIES IN THE CENTRAL US IN DJF AND JFM AND THE DRY ANOMALY IN SOUTHERN TEXAS IN NDJ. DRY ANOMALIES SPREAD EASTWARD FROM THE SOUTHWEST TO TEXAS IN OND AND INCLUDE FLORIDA BY NDJ. TEXAS AND SW ANOMALIES DIE OUT AFTER NDJ - BUT CONTINUE IN FLORIDA THROUGH JFM. THESE ANOMALIES - AND THEIR EVOLUTION DURING FALL AND WINTER - ARE CONSISTENT WITH COLD EVENT CONDITIONS AND ARE SUPPORTED BY TREND-ADJUSTED ENSO COMPOSITES. TREND-ADJUSTED ENSO-NEUTRAL COMPOSITES AND CCA ARE USED FOR FORECASTS FROM FMA THROUGH JJA 2004. . . . . . . . . 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: E. OLENIC 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 JUNE 19 2003. 1971-2000 BASE PERIOD MEANS WERE IMPLEMENTED EFFECTIVE WITH THE MAY 17 2001 FORECAST RELEASE. NOTE - AREAS OF UNCERTAINTY THAT FORMERLY WERE LABELED CL (CLIMATOLOGICAL PROBABILITIES) ARE NOW LABELED EC (EQUAL CHANCES). $$