PROGNOSTIC DISCUSSION FOR LONG-LEAD SEASONAL OUTLOOKS NWS CLIMATE PREDICTION CENTER CAMP SPRINGS MD 300 PM EST THU NOVEMBER 20 2003 . . . . . . . . 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 OR WEAK WARM EVENT CONDITIONS IN THE TROPICAL PACIFIC DURING THE NEXT SEVERAL MONTHS. A WEAK WARM EVENT - SHOULD IT DEVELOP - IS NOT LIKELY TO HAVE A MAJOR IMPACT ON US CLIMATE THIS WINTER. THE RAPID COOLING TREND TOWARDS LA NINA IN THE EQUATORIAL PACIFIC DURING JANUARY THROUGH MAY WAS FOLLOWED BY WARMING DURING JUNE AND EARLY JULY. AS OF MID-NOVEMBER...SURFACE AND SUBSURFACE TEMPERATURES IN THE EQUATORIAL PACIFIC ARE SLIGHTLY ABOVE THE LONG TERM AVERAGE. A MINOR WARM EVENT FOR WINTER 2003/04 IS POSSIBLE BUT FOR NOW WE ASSUME NEUTRAL CONDITIONS. THE OUTLOOK FOR DECEMBER THROUGH FEBRUARY 2003/04 CALLS FOR BETTER THAN AVERAGE ODDS OF ABOVE NORMAL TEMPERATURES OVER THE THE WESTERN TWO-THIRDS OF THE NATION. BELOW-MEDIAN PRECIPITATION IS MORE LIKELY THAN AVERAGE OVER CALIFORNIA - FLORIDA AND SOUTH GEORGIA DURING DJF. ABOVE-MEDIAN PRECIPITATION HAS ENHANCED LIKELIHOOD OVER TEXAS AND SOUTHERN OKLAHOMA PLUS PORTIONS OF ADJACENT STATES. . . . . . . . . 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-NOVEMBER WEEKLY AVERAGES OF SST SHOW POSITIVE ANOMALIES ALONG THE EQUATOR IN THE PACIFIC FROM A FEW TENTHS IN THE TO MORE THAN ONE DEGREE C. THE MOST CONSISTENTLY WARM AND APPARENTLY GROWING REGION OF ABNORMALLY WARM SURFACE WATER LIES ALONG THE EQUATOR BETWEEN 175W AND 160E. MUCH OF THE REGION ABOVE THESE ANOMALIES HAS SUB-NORMAL CONVECTION - AS OF THE MID-NOVEMBER TAO TEMPERATURE AND CPC OLR OBSERVATIONS. THE OLR PATTERN IS ASYMMETRIC WITH RESPECT TO THE EQUATOR AND DOES NOT RESEMBLE A TYPICAL ENSO PATTERN. THESE OBSERVATIONS SUPPORT THE ASSUMPTION OF ENSO-NEUTRAL CONDITIONS AT LEAST DURING THE EARLY LEADS OF THIS OUTLOOK. THE TRADE WINDS ARE CLOSE TO SEASONAL AVERAGE VALUES OVER THE TROPICAL PACIFIC. THE NINO3.4 TEMPERATURE ANOMALY HAS DECLINED SLIGHTLY FROM ONE MONTH AGO - BUT IS VERY CLOSE TO +0.5. WHILE WE ARE - TECHNICALLY - NEARING A WEAK EL NINO IMPACTS ON THE TROPICAL ATMOSPHERE AND ELSEWHERE ARE NOT EVIDENT. . . . . . . . . PROGNOSTIC DISCUSSION OF SST FORECASTS FORECASTS FROM MULTIPLE MODELS GIVE A RANGE OF POSSIBLE FUTURE SST PATTERNS IN THE TROPICAL PACIFIC WITH THE NINO 3.4 SST ANOMALY WITHIN THE RANGE OF 0.0 TO O.9. MOST PROJECTIONS FALLING WITHIN THE ENSO-NEUTRAL RANGE. TO SEE THESE FORECASTS GO TO: http://www.cpc.ncep.noaa.gov/products/predictions/90day/tools/briefing/plume.gif A CONSOLIDATION FORECAST OF IN-HOUSE TOOLS INDICATES THAT NINO 3.4 SST ANOMALIES WILL REMAIN NEAR ZERO THROUGH SPRING 2004 - WITH THE ODDS FOR NEUTRAL CONDITIONS REACHING 85% IN DJF AND 76% IN JFM. CONFIDENCE IN THE SST FORECAST IS HIGH THROUGH NEXT SUMMER AND DECREASES THEREAFTER. SSTA FORECASTS FOR THE NINO 3.4 REGION BY MODELS RUN IN OTHER CENTERS GENERALLY FALL IN THE ENSO-NEUTRAL RANGE AS WELL. AS A MATTER OF PROBABILITY FORECAST THIS DOES NOT RULE OUT A WEAK WARM EVENT...SO STAY TUNED. 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 - IRI AND CDC- WERE EXAMINED FOR THE PERIOD DJF 2003 THROUGH MAM 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 PRIMARY TOOLS USED IN THE DJF THROUGH MAM FORECASTS WERE OCN AND CCA - TWO-TIER FORECASTS FROM SIX MODELS PROVIDED BY CDC - DYNAMICAL MULTI-MODEL ENSEMBLES FROM IRI AND DYNAMICAL MODEL FORECASTS FROM NCEPS ENVIRONMENTAL MODELING CENTER. THESE ARE LISTED IN ORDER FROM HIGHEST TO LOWEST WEIGHT. THE IMPACT OF OCN AND CCA IS VISIBLE IN THE SOUTHERN AND WESTERN US AND IN ALASKA DJF THROUGH MAM TEMPERATURE FORECASTS AND IN DJF AND JFM FORECASTS FOR TEXAS AND THE GREAT PLAINS. THERE WAS VERY GOOD AGREEMENT AMONG CDC AND IRI DYNAMICAL MODELS ON THE UPPER AIR HEIGHT PATTERN DURING THE WINTER - AN AMPLIFIED PATTERN WITH A DEEP ANOMALOUS TROUGH SOUTHWEST OF THE ALEUTIANS - A POSITIVE HEIGHT ANOMALY ALONG THE WEST COAST OF NORTH AMERICA AND A NEGATIVE ANOMALY CENTERED OVER THE GULF OF ST LAWRENCE. THE PATTERN SUGGESTED BY THESE FORECASTS IS RELATED TO ABNORMAL WARMTH IN THE FAR WEST - UNCERTAIN CONDITIONS IN THE INTER-MOUNTAIN WEST - ABNORMAL WARMTH IN THE GREAT PLAINS AND MIXED TEMPERATURES IN THE EAST - DRIER THAN AVERAGE CONDITIONS IN CALIFORNIA AND FLORIDA AND WETTER THAN AVERAGE CONDITIONS IN THE NORTHWEST AND IN TEXAS. NCEPS OLDER - TWO-TIER DYNAMICAL CLIMATE MODEL - THE SEASONAL FORECAST MODEL (SFM) IS IN OVERALL AGREEMENT WITH THE CDC FORECASTS - WHILE THE NEW CLIMATE FORECAST SYSTEM (CFS) IS OUT OF PHASE DURING DJF BUT IS IN BETTER AGREEMENT IN SUBSEQUENT SEASONS. THE CFS SST FORECAST WAS ALSO AT ODDS WITH FORECASTS FROM THE SFM AND FROM CDC. IT PREDICTED ABNORMAL WARMTH EAST OF THE DATELINE BUT PREDICTED SMALL COLD ANOMALIES TO THE WEST - WHERE OTHER MODELS PREDICT PERSISTENCE OF POSITIVE ANOMALIES. IRIS MULTI-MODEL ENSEMBLE INDICATES MUCH SMALLER UPPER AIR HEIGHT ANOMALIES OVER NORTH AMERICA THAN THE OTHER MODELS - THOUGH THE ECHAM MEMBER IS IN OVERALL AGREEMENT WITH CDC AND NCEP-SFM. . . . . . . . . PROGNOSTIC DISCUSSION OF OUTLOOKS - DJF 2003-4 TO DJF 2004-5 TEMPERATURE: WE CONSIDERED NEGATIVE ANOMALIES FOR THE NORTHEAST WHICH IS A POSSIBILITY IF CONVECTION WERE TO BECOME SETTLED NEAR OR WEST OF THE DATELINE AND A POSITIVE PNA SETS UP. HOWEVER - GIVEN TRENDS FOR ABNORMAL WARMTH - EC IS ASSIGNED TO MUCH OF THE EAST. FOR DJF THE TREND INDICATES POSITIVE ANOMALIES CENTERED OVER PARTS OF THE SOUTHWEST - INTERIOR ALASKA - AND FLORIDA. IN MANY AREAS THE INDICATIONS FOR WARMTH ARE SUPPORTED BY CCA. POSITIVE TEMPERATURE ANOMALIES ELSEWHERE ARE FROM A CONSENSUS OF THE DYNAMICAL MODELS. FROM JFM THROUGH MAM TEMPERATURE FORECASTS ARE BASED PRIMARILY UPON CCA... OCN... AND DYNAMICAL MODELS WITH SOME INPUT FROM A COMPOSITE OF PAST CASES FOR TREND-ADJUSTED ENSO-NEUTRAL CONDITIONS. WARMER THAN AVERAGE TEMPERATURES ARE PREDICTED IN ALASKA LASTING THROUGH SUMMER 2004 DUE TO OCN - CCA AND DYNAMICAL MODELS. OVER THE CONUS THE STRONGEST MOST CONFIDENT INDICATIONS - ALL WARM - ARE FOUND MAINLY IN THE SOUTH AND SOUTHWEST DURING WINTER...IN THE SOUTHWEST AND WEST IN SPRING...AND IN THE SOUTH AND SOUTHWEST AGAIN IN SUMMER. TRENDS ALONE...AS WELL AS CCA...WOULD FAVOR MUCH OF THE EASTERN HALF OF THE NATION TO HAVE ABOVE NORMAL TEMPERATURES DURING THE WINTER SEASONS...BUT THE ENSO-NEUTRAL COMPOSITES AND UNCERTAINTY IN THE AO AND NAO CAUSED US TO PUT EC IN SOME OF THOSE REGIONS - THOUGH POSITIVE ANOMALIES COVER MORE OF THE CENTRAL US IN THIS MONTHS FORECAST - DUE MAINLY TO TREND AND DYNAMICAL MODELS. FORECAST FOR BELOW IN THE DAKOTAS IN AMJ IS DUE TO TRENDS. FORECASTS BEGINNING WITH AMJ ARE BASED LARGELY ON OCN AND CCA FORECASTS...AND FOR THE SUMMER 2004 SEASONS INDICATE WARMTH OVER THE SOUTHWEST...SOUTHEAST... AND PACIFIC COAST FROM OCN WITH SOME SUPPORT FROM CCA. . . . . . . . . PRECIPITATION: ABOVE-MEDIAN PRECIPITATION IS FORECAST FOR DJF THROUGH FMA IN PORTIONS OF THE SOUTHERN GREAT PLAINS AND LOWER MISSISSIPPI VALLEY BASED ON OCN AND DYNAMICAL MODELS. INDICATIONS FOR BELOW-MEDIAN PRECIPITATION OVER PORTIONS OF THE SOUTHWEST WERE ALSO BASED ON OCN - DYNAMICAL MODELS AND TREND-ADJUSTED ENSO-NEUTRAL CONDITIONS. BELOW-MEDIAN PRECIPITATION FOR FLORIDA AND SOUTHERN GEORGIA IS SUPPORTED NOT ONLY BY TRENDS BUT ALSO BY DYNAMICAL MODELS. ACCORDING TO DYNAMICAL MODEL STUDIES - THIS HAPPENS IF CONVECTION STAYS A CERTAIN DISTANCE WEST OF THE DATE LINE. AN AREA OF ABOVE-MEDIAN PRECIPITATION IS FORECAST FOR THE PACIFIC NORTHWEST DURING AMJ AND MJJ BASED ON OCN...TREND COMPOSITES FOR ENSO-NEUTRAL CONDITIONS...AND CCA. THERE WERE FEW RELIABLE PRECIPITATION SIGNALS FOR JJA THROUGH SON 2004...WITH THE EXCEPTION OF DRYNESS IN PORTIONS OF THE FAR WEST DURING JAS AND WETNESS NEAR THE NEBRASKA WYOMING BORDER IN ASO AND SON INDICATED BY THE TREND-ADJUSTED ENSO-NEUTRAL COMPOSITES WITH SOME SUPPORT FROM OCN. BY OND AND NDJ 2004 SOME OF THE TRENDS FOR WET RETURN TO THE SOUTHERN PLAINS. FORECAST INDICATIONS FOR PRECIPITATION ARE TYPICALLY UNCERTAIN IN MOST OF ALASKA...AND WITH THE EXCEPTION OF STRONGLY-FORCED COLD SEASON PATTERNS DURING EL NINO EVENTS AND USUALLY HAVE RATHER LOW SKILL ESPECIALLY IN THE WARM SEASONS. THEREFORE THE ENTIRE STATE WAS LEFT EC FOR PRECIPITATION AT ALL LEADS. NOTE - AREAS OF UNCERTAINTY THAT FORMERLY WERE LABELED CL (CLIMATOLOGICAL PROBABILITIES) ARE NOW LABELED EC (EQUAL CHANCES). . . . . . . . . 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 DEC 18 2003. 1971-2000 BASE PERIOD MEANS WERE IMPLEMENTED EFFECTIVE WITH THE MAY 17 2001 FORECAST RELEASE. $$