PROGNOSTIC DISCUSSION FOR LONG-LEAD SEASONAL OUTLOOKS NWS CLIMATE PREDICTION CENTER CAMP SPRINGS MD 830 AM EDT THU APRIL 15 2004 . . . . . . . . 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. SSTS IN THE TROPICAL PACIFIC REMAIN BELOW THE THRESHOLD REQUIRED TO PRODUCE ENSO IMPACTS ON THE US CLIMATE. IN FACT - SSTS IN THE ENSO-RELEVANT REGION HAVE MOVED EVEN CLOSER TO NORMAL THAN THEY WERE LAST MONTH. CLIMATE MODELS FROM NCEP - CDC - IRI AND ECMWF INDICATE CONTINUATION OF NEAR- NEUTRAL TROPICAL SSTS AT LEAST THROUGH THE SUMMER. THESE MODELS ALL TEND TO AGREE ON THE LIKELY OCCURRENCE OF A REGION OF ABNORMAL DRYNESS OVER THE SOUTH- EASTERN US DURING MJJ. ANOTHER REGION OF ABNORMAL DRYNESS IS LIKELY OVER THE NORTHWEST US DURING JAS AND ASO. EQUAL CHANCES IS GIVEN FOR THE THREE POSSIBLE CATEGORIES OF PRECIPITATION (ABOVE - MEDIAN - BELOW) OVER ALASKA BEYOND JAS 2004 AND OVER THE CONUS BEYOND ASO 2004. RELATIVELY WARM CONDITIONS ARE LIKELY OVER MUCH OF THE WEST - THE SOUTHWEST - SOUTHERN TEXAS - THE GULF COAST STATES AND FLORIDA DURING MJJ THROUGH SON. REMAINING AREAS NOT MENTIONED HAVE EQUAL ODDS FOR EACH OF THE THREE CATEGORIES OF TEMPERATURE AND 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 AS OF MID-APRIL WEEKLY AVERAGES OF SST SHOW TEMPERATURE ANOMLIES IN THE NEUTRAL RANGE ACROSS MUCH OF THE TROPICAL PACIFIC - INCLUDING ALONG THE WEST COAST OF SOUTH AMERICA. EXCEPTIONS INCLUDE A SMALL REGION OF 0.5 TO 1.0 DEGREE ANOMALIES WEST OF ABOUT 145E - AND A SMALL REGION OF -0.5 TO -1.0 DEGREE ANOMALIES BETWEEN ABOUT 130 AND 100W. A 5-DAY MEAN TOGA-TAO DEPTH-LONGITUDE CROSS-SECTION SHOWS ABNORMALLY WARM WATER - WITH ANOMALIES OF UP TO 2 C - CENTERED ABOUT 125 METERS BELOW THE SURFACE WEST OF ABOUT 160W AND A REGION OF ABNORMALLY COLD WATER TO THE EAST OF 160W - SLOPING UPWARD TOWARD THE EAST - FROM A DEPTH OF 125 METERS AT 160W (WITH 1 C ANOMALIES) - TO A DEPTH OF 50 METERS (WITH -2 C ANOMALIES) BETWEEN 120W AND THE SOUTH AMERICAN COAST. THIS ARRANGEMENT OF ANOMALIES MAKES FOR A LARGER-THAN- AVERAGE TILT IN THE THERMOCLINE - FROM DEEPER THAN NORMAL IN THE WEST TO SHALLOWER THAN NORMAL IN THE EAST. THE TRADE WINDS HAVE AN ABNORMAL WESTERLY COMPONENT NEAR ABOUT 160E. ELSEWHERE TRADE WINDS ARE CLOSE TO NORMAL. A BURST OF WESTERLY WINDS OVER THE FAR WESTERN SECTION OF THE TROPICAL PACIFIC OCCURED DURING EARLY APRIL. A REGION OF ENHANCED CONVECTION CURRENTLY RESIDES BETWEEN 145E AND THE DATELINE. THIS REGION HAS SHIFTED EASTWARD OVER THE PAST MONTH. ELSEWHERE IN THE TROPICAL PACIFIC OLR IS SUB-NORMAL. . . . . . . . . PROGNOSTIC DISCUSSION OF SST FORECASTS FORECASTS FROM MULTIPLE MODELS GIVE A RANGE OF POSSIBLE FUTURE SST ANOMALIES IN NINO 3.4 OF -0.3 TO +1.0 C FOR THE NEXT FEW SEASONS. THE CONSENSUS OF THE MODEL SST FORECASTS FALLS WITHIN THE ENSO-NEUTRAL RANGE FROM THEN THROUGH NEXT FALL. TO SEE THESE FORECASTS GO TO: 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 REMAIN SLIGHTLY ABOVE ZERO THROUGH SPRING 2004 - WITH THE ODDS FOR NEUTRAL CONDITIONS REACHING 85% IN MJJ - 80% IN JJA AND 75% IN JAS - WHILE THE ODDS OF LA NINA ARE 10% IN MJJ - 15% IN JJA AND 20% IN JAS. THE ODDS FOR EL NINO ARE A CONSTANT 5% IN MJJ - 5% IN JJA AND 5% IN JAS. BY NEXT WINTER - THE CONSENSUS IS STILL WITHIN THE NEUTRAL RANGE. WE EXPECT THAT TRANSIENT ATMOSPHERIC CIRCULATION PATTERNS WILL CONTINUE TO BE FORCED PRIMARILY BY INTRA-SEASONALLY VARYING PHASES OF THE MJO. PROGNOSTIC TOOLS USED FOR U.S. TEMPERATURE AND PRECIPITATION OUTLOOK THE PRIMARY TOOLS USED IN THE MJJ THROUGH ASO FORECASTS WERE OCN AND CCA. CONSULTED - BUT NOT USED SIGNIFICANTLY 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. 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. ALSO - SOME CONSIDERATION WAS GIVEN TO COMPOSITE OBSERVED TEMPERATURE AND PRECIPITATION ANOMALY PATTERNS OVER THE CONUS FOR PAST CASES OF NEUTRAL SST PATTERNS OVER THE EQUATORIAL PACIFIC. THE IMPACT OF OCN AND CCA IS VISIBLE IN THE SOUTHERN AND WESTERN US AND IN ALASKA JFM THROUGH AMJ TEMPERATURE FORECASTS AND TO A LESSER EXTENT IN THE PRECIPITATION FORECASTS FOR THESE SAME SEASONS. CCA AND OCN ARE THE ONLY TOOLS USED BEYOND THE FOURTH LEAD. THE CONSTRUCTED ANALOG FORECAST AND THE ENSEMBLE CCA BOTH PREDICTED COLD IN THE WEST AND WARM IN THE EAST. CA ALSO PREDICTED ABNORMAL WETNESS IN TEXAS. THESE TOOLS - THOUGH OF GREAT INTEREST - WERE NOT USED AS PRIMARY INPUTS - THOUGH PROBABILITIES OF ABOVE NORMAL TEMPERATURE IN TEXAS WERE REDUCED COMPARED WITH LAST MONTHS FORECAST IN ACNOWLEDGMENT OF THE CA AND ECCA FORECASTS. BECAUSE THE STATUS OF ENSO IS NEUTRAL AND WE ARE IN THE SPRING BARRIER PERIOD - FORECASTS FROM THE DYNAMICAL MODELS ARE NOT THE MAIN INPUTS TO THIS FORECAST. ONE EXCEPTION IS THE PRECIPITATION FORECAST FOR MJJ IN THE SOUTHEAST - WHERE A STRONG CONSENSUS AMONG DYNAMICAL MODELS AND THE CCA FORECAST FROM CDC PROMPT A FORECAST FOR ENHANCED LIKELIHOOD OF SUB-MEDIAN PRECIPITATION. . . . . . . . . PROGNOSTIC DISCUSSION OF OUTLOOKS - MJJ 2005 TO MJJ 2006 TEMPERATURE: CCA AND OCN ARE THE MAIN TOOLS USED HERE. FOR MJJ 2005 CCA AND OCN INDICATE ABOVE NORMAL TEMPERATURES FOR MUCH OF ALASKA - THE COASTAL NORTHWEST AND SECTIONS OF THE SOUTHERN U.S. FROM CALIFORNIA TO THE SOUTHEAST. THIS OVERALL WARM - AND LARGELY TREND - SIGNAL FADES FROM ALASKA IN JJA 2004 THROUGH MAM 2005 BUT RETURNS IN AMJ AND MJJ 2005. OVER THE CONTINENTAL U.S. THE EXCESS WARMTH EXPANDS IN JJA TO BECOME CONTINUOUS ALONG THE WEST COAST - AND TO COVER ALL OF THE SOUTHWEST - THE SOUTHERN GREAT PLAINS - THE SOUTH AND THE OHIO AND MISSISSIPPI VALLEYS. IN JAS THE EXCESS WARMTH - REMAINS IN THESE AREAS - SHRINKING IN SIZE AND LIKELIHOOD IN THE EAST AND GETTING MORE LIKELY AND LARGER IN AREA - IN THE WEST. BY ASO ABNORMAL WARMTH COVERS CENTRAL AND SOUTHERN SECTIONS OF THE WEST - THE ROCKIES AND WESTERN SECTIONS OF THE CENTRAL AND SOUTHERN GREAT PLAINS - AS WELL AS SOUTHERN FLORIDA. BY SON THE TREND FOR ABNORMAL WARMTH RETREATS TO A SMALL SECTION OF THE INTERIOR SOUTHWEST CENTERED ON ARIZONA - SOUTHERN FLORIDA ALSO REMAINS IN THE ABOVE NORMAL CLASS. THE CCA-OCN SIGNAL FADES TO EC 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. IN DJF THIS REGION GETS COMPANY FROM THE NORTHEAST - THE GREAT LAKES THE OHIO VALLEY AND TENNESSEE AND EASTERN SECTIONS OF THE NORTHERN AND CENTRAL GREAT PLAINS. THE CCA-OCN SIGNAL PEAKS IN JFM 2005 - WHEN MUCH OF THE NATION IS LIKELY TO HAVE ABOVE NORMAL TEMPERATURES THAN IN ANY OTHER SEASON. CCA-OCN INDICATES ABNORMAL WARMTH ONLY IN THE WEST IN FMA AND MAM AND IN THE WEST AND SOUTHERN ALASKA IN AMJ 2005. IN THE FINAL LEAD - MJJ 2005 - THE CCA-OCN COMBINED TOOL INDICATES ENHANCED LIKELIHOOD FOR ABNROMAL WARMTH IN THE SOUTHEAST - SECTIONS OF THE INTERIOR SOUTHWEST AND TEXAS - COASTAL SECTIONS OF THE NORTHWEST AND IN SOUTHERN ALASKA. . . . . . . . . PRECIPITATION: A CONSENSUS OF MODELS INDICATES AN ENHANCED LIKELIHOOD OF SUB-MEDIAN PRECIPITATION IN THE SOUTHEAST IN MJJ. IN JAS AND ASO OCN AND CCA INDICATE ENHANCED LIKELIHOOD OF SUB-MEDIAN PRECIPITATION IN SECTIONS OF THE NORTHWEST. ELSEWHERE AND FOR OTHER SEASONS NOT MENTIONED EC IS INDICATED. NOTE - AREAS OF UNCERTAINTY THAT FORMERLY WERE LABELED CL (CLIMATOLOGICAL PROBABILITIES) ARE NOW LABELED EC (EQUAL CHANCES). . . . . . . . . FORECASTER: E. OLENIC 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 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 - 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 MAY 20 2004. 1971-2000 BASE PERIOD MEANS WERE IMPLEMENTED EFFECTIVE WITH THE MAY 17 2001 FORECAST RELEASE. $$