PROGNOSTIC DISCUSSION FOR LONG-LEAD SEASONAL OUTLOOKS NWS CLIMATE PREDICTION CENTER CAMP SPRINGS MD 830 AM EDT THU JUL 21 2005 NOTICE: THE OUTLOOK MAPS ISSUED JULY 21 CONTAINED SEVERAL SMALL ERRORS WHICH HAVE BEEN CORRECTED WITH A RE-ISSUANCE OF THE MAPS. MAPS AFFECTED INCLUDE ASO 2005 T - REMOVED WARM ANOMALY FROM SOUTHERN FLORIDA, - ADDED MODEST WARM ANOMALY TO THE REGION BETWEEN TX AND MO ASO 2006 P - ADDED AREA OF DRY ANOMALY TO NV. SUMMARY OF THE OUTLOOK FOR NON-TECHNICAL USERS SEA SURFACE TEMPERATURES (SSTS) IN THE EQUATORIAL PACIFIC ARE SLIGHTLY ABOVE NORMAL HOWEVER WITH SOME CHANGES FROM WEEK TO WEEK. SUBSURFACE OCEAN TEMPERATURES IN THE UPPER LAYERS OF THE EASTERN PACIFIC ARE ALSO QUITE CLOSE TO NORMAL... INDICATING THAT NEUTRAL ENSO CONDITIONS WILL LIKELY PERSIST FOR THE NEXT FEW MONTHS. THERE IS MODEST CONSENSUS AMONG BOTH STATISTICAL AND DYNAMICAL ENSO PREDICTION MODELS FOR NEUTRAL CONDITIONS TO PREVAIL THROUGH EARLY 2006. SSTS THROUGHOUT THE TROPICAL NORTH ATLANTIC OCEAN EXTENDING INTO THE CARIBBEAN SEA ARE WELL ABOVE NORMAL AND ARE EXPECTED TO FAVOR AN ACTIVE ATLANTIC HURRICANE SEASON... AND THIS WILL IMPACT THE SEASONAL PRECIPITATION PREDICTION FOR THE SOUTHEASTERN U.S. THIS FALL. THE OUTLOOKS FOR ASO 2005 THROUGH JFM 2006 ARE BASED ON A WIDE ARRAY OF DYNAMICAL AND STATISTICAL TOOLS. OUTLOOKS FOR FMA 2006 AND BEYOND ARE BASED MAINLY ON TRENDS WITH SOME INPUT FROM OTHER STATISTICAL TOOLS. WITH ENSO EXPECTED TO BE IN ITS NEUTRAL PHASE THROUGH AT LEAST SPRING 2006.. THERE ARE NO STRONG PREDICTIVE SIGNALS FOR CLIMATE ANOMALIES IN THIS SET OF FORECASTS. THE MOST CONFIDENT SIGNALS ARE FOR ABOVE NORMAL TEMPERATURES AT THE FEW SEASONS AND LOCATIONS WHERE TRENDS ARE STRONG. A CONSENSUS OF MODELS INDICATE A WEAK SOUTHWESTERN MONSOON ... FAVORING DRY CONDITIONS IN THE SOUTHWESTERN U.S. AND THE GREAT BASIN FOR ASO 2005. THE ACTIVE HURRICANE SEASON INCREASES THE CHANCES FOR ABOVE MEDIAN PRECIPITATION AMOUNTS IN THE SOUTHEASTERN U.S.. IT SHOULD BE EMPHASIZED THAT THERE IS NO RELIABLE WAY TO PREDICT THE FORMATION AND MOVEMENT OF INDIVIDUAL TROPICAL STORMS BEYOND ABOUT A WEEK... AND THE PRECIPITATION OUTLOOK IN THE SOUTHEAST REFLECTS RAINFALL AMOUNTS RECEIVED IN ACTIVE HURRICANE SEASONS IN THE PAST AS WELL AS RECENT TRENDS IN FLORIDA. THE TEMPERATURE OUTLOOKS PRIMARILY REFLECT RECENT TEMPERATURE TRENDS WITH SOME REVISIONS IN THE FIRST FEW LEAD TIMES BASED ON STATISTICAL AND DYNAMICAL TOOLS. WARMER THAN NORMAL SSTS ALONG THE WEST COAST OF NORTH AMERICA AND ALASKA CONTRIBUTE TO EXPECTED ABOVE NORMAL TEMPERATURES IN THE PACIFIC NORTHWEST AND SOUTHERN ALASKA FOR ASO 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 SSTS ALONG THE EQUATOR ARE ABOUT .5 DEGREES C BELOW NORMAL NEAR THE SOUTH AMERICAN COAST AND GENERALLY ABOUT .5 DEGREES C ABOVE NORMAL FROM 130W TO INDONESIA. OCEAN TEMPERATURES IN THE UPPER 200 METERS THROUGHOUT THE EAST-CENTRAL EQUATORAL PACIFIC ARE QUITE CLOSE TO NORMAL. ATMOSPHERIC INDICATORS SUCH AS TRADE WINDS AND CONVECTION IN THE EQUATORIAL PACIFIC ARE ALSO CLOSE TO NORMAL AND SUGGEST... TOGETHER WITH THE OCEAN STATE ... THAT NEUTRAL ENSO CONDITIONS WILL LIKELY PREVAIL IN THE NEXT FEW MONTHS. THERE IS AN EXTENSIVE AREA OF ABOVE NORMAL SSTS IN THE (SUB)TROPICAL ATLANTIC OCEAN AND THE CARIBBEAN SEA. THE UNUSUALLY WARM SSTS COVER NEARLY THE ENTIRE DEVELOPMENT REGION FOR ATLANTIC BASIN TROPICAL STORMS AND ARE EXPECTED TO FURTHER ENHANCE THE DECADAL SIGNAL TOWARD ACTIVE HURRICANE SEASONS. THE CPC OUTLOOK FOR ATLANTIC BASIN TROPICAL STORMS SUGGEST A 70 PERCENT CHANCE OF ABOVE NORMAL TROPICAL STORM ACTIVITY FOR THE 2005 HURRICANE SEASON. . . . . . . . . PROGNOSTIC DISCUSSION OF SST FORECASTS THE CONSENSUS OF SEVERAL MODELS USED AT CPC SHOWS SEASONAL MEAN NINO 3.4 SST ANOMALIES REMAINING CLOSE TO LONG TERM AVERAGES FOR THE REMAINDER OF THE YEAR. BUT THERE IS SPREAD RANGING FROM +1 BY CCA TO -0.5 BY CFS. A CONSENSUS OF LOCALLY RUN PREDICTION TOOLS FOR THE NINO 3.4 REGION SHOWS SSTS HOLDING STEADY AT AROUND .3 DEGREES C ABOVE NORMAL THROUGH THE EARLY PART OF 2006. PROGNOSTIC TOOLS USED FOR U.S. TEMPERATURE AND PRECIPITATION OUTLOOKS THE OUTLOOK FOR ASO 2005 THROUGH JFM 2006 IS BASED ON THE MULTI-MODEL ENSEMBLE FROM IRI... THE CFS... AND STATISTICAL TOOLS... INCLUDING CCA... SMLR AND OCN. INPUT FROM CDC - WARM AND DRY PRACTICALLY EVERYWHERE - WAS CONSULTED. ECCA WAS USED FOR ASO. OCN IS THE PRIMARY TOOL EXPLICITLY USED FROM JFM THROUGH ASO 2006. AND BECAUSE ENSO IS WEAK ALL FORECASTS REFLECT INTERDECADAL TREND MORE THAN ANY OTHER FACTORS. . . . . . . . . PROGNOSTIC DISCUSSION OF OUTLOOKS - ASO 2005 TO ASO 2006 TEMPERATURE: FOR THE FIRST LEAD SOME CHANGES WERE MADE RELATIVE TO THE 1.5 MONTH LEAD ASO FORECAST MADE LAST MONTH. WE REMOVED THE INDICATIONS FOR ABOVE NORMAL IN SOUTHERN FLORIDA BECAUSE THE PREVIOUSLY OBSERVED LONG TERM TREND FOR ABOVE NORMAL TEMPERATURE HAS NOT BEEN OBVIOUS LATELY AND SST ARE NOT ABOVE NORMAL IN THE ADJACENT GULF. WE ALSO REMOVED THE EC AREA ALONG THE TEXAS-MISSOURI AXIS ... CHANGIN THA REGION TO WEAK ABOVE NORMAL. THE INTERIOR NW IS INDICATED AS COLD BY SEVERAL TOOLS SO WE REDUCED THE DEGREE OF WARMTH IN COMPARISON WITH PREVIOUS FORECASTS. WE ADDED SOME WARMTH DUE TO TRENDS IN NEW ENGLAND. THERE IS A STRONG CONSENSUS AMONG TOOLS FOR ABOVE NORMAL TEMPERATURES IN THE SOUTHWESTERN U.S. IN ALL SEASONS WITH OCCASIONAL EXTENSIONS INTO TEXAS AND PORTIONS OF THE GULF COAST. THERE IS A BROAD CONSENSUS AMONG TOOLS FOR ABOVE NORMAL TEMPERATURES IN COASTAL REGIONS OF THE PACIFIC NORTHWEST AND THE SOUTH COAST OF ALASKA... WITH CONFIDENCE INCREASED IN THE SHORT RANGE BY WARM SSTS IN THE GULF OF ALASKA. CCA AND OCN SHOW GOOD CHANCES FOR ABOVE NORMAL TEMPERATURES IN MUCH OF THE WESTERN U.S. AND ALASKA. FOR MAM 2006 WE FOLLOWED INDICATIONS FOR BELOW NORMAL IN THE NORTHERN PLAINS. NOTE THAT THIS IS THE ONLY PLACE AND TIME WHERE WE FAVOR PROBABILITIES FOR BELOW NORMAL. . . . . . . . . PRECIPITATION: THERE IS A FAIR AMOUNT OF CONSENSUS AMONG DYNAMIC MODELS FOR BELOW MEDIAN PRECIPITATION AMOUNTS IN THE SOUTHWESTERN U.S FOR ASO 2005. THIS IS CONSISTENT WITH THE WEAK MONSOON WE HAVE SEEN SO FAR. WE EXTENDED THE AREAL COVERAGE FOR THE BELOW MEDIAN IN THE SW BECAUSE OF MULTI-MODEL INPUT. WE CONTINUE ABOVE-MEDIAN RAINFALL AMOUNTS FOR ASO IN THE SOUTHEASTERN U.S. DUE TO THE EXPECTED ENHANCED TROPICAL ACTIVITY. NO CHANGES WERE MADE THERE. THE AREAS OF ABOVE MEDIAN PRECIPITATION FORECAST OVER EAST TEXAS AND THE SOUTHERN PLAINS FROM OND 2005 THROUGH DJF 2006 COME FROM OCN. THERE ARE VERY FEW RELIABLE TRENDS IN PRECIPITATION EVIDENT ANYWHERE ACROSS THE COUNTRY BETWEEN JFM AND JJA 2006... AND IN THE ABSENCE OF ANY CLEAR-CUT INDICATIONS FROM ENSO... THE PRECIPITATION MAPS FOR THOSE SEASONS ARE LEFT WITH EC NEARLY EVERYWHERE. THE ONLY EXCEPTION ARE INDICATIONS FOR ABOVE NORMAL PRECIPITATION IN THE NORTHWEST IN LATE SPRING AND EARLY SUMMER. TRENDS SUGGEST INCREASED CHANCES FOR ABOVE MEDIAN RAINFALL IN FLORIDA... AND BELOW MEDIAN PRECIPITATION OVER PORTIONS OF THE WEST FOR JAS AND ASO 2006. 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. CFS - CLIMATE FORECAST SYSTEM - A FULLY-COUPLED OCEAN-ATMOSPHERE FORECAST SYSTEM WHICH USES NO ADJUSTMENTS TO OCEAN-ATMOSPHERE FLUXES IN POST- PROCESSING (A ONE-TIER SYSTEM) DEVELOPED AT THE NATIONAL CENTERS FOR ENVIRONMENTAL PREDICTION. 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. ECCA - ENSEMBLE CCA. A MULTI-VARIATE STATISTICAL FORECAST BASED ON THE PAST PERFORMANCE OF THE CFS MODEL FORECAST USING THE MOST RECENT FORECAST AS THE PREDICTOR. 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 AUG 18 2005. 1971-2000 BASE PERIOD MEANS WERE IMPLEMENTED EFFECTIVE WITH THE MAY 17 2001 FORECAST RELEASE. $$