PROGNOSTIC DISCUSSION FOR LONG-LEAD SEASONAL OUTLOOKS NWS CLIMATE PREDICTION CENTER CAMP SPRINGS MD 830 AM EST THU FEBRUARY 17 2005 . . . . . . . . SUMMARY OF THE OUTLOOK FOR NON-TECHNICAL USERS CURRENT OBSERVATIONS INDICATE THAT THE WEAK WARM EPISODE CONDITIONS (EL NINO) THAT HAVE PREVAILED OVER THE EQUATORIAL PACIFIC FOR THE PAST FEW MONTHS ARE BEGINNING TO FADE. THE LARGE AREA OF ABOVE NORMAL SSTS NEAR THE DATE LINE HAS DIMINISHED IN BOTH SIZE AND INTENSITY... AND SSTS ALONG THE EQUATOR ARE MORE THAN 0.5 C BELOW NORMAL FROM THE SOUTH AMERICAN COAST AS FAR WEST AS ABOUT 100W. A CONSENSUS OF SEA SURFACE TEMPERATURE (SST) PREDICTION TOOLS INDICATE THAT THERE WILL BE A GRADUAL TRANSITION FROM WEAK WARM EPISODE CONDITIONS TO ENSO-NEUTRAL CONDITIONS WITHIN THE NEXT THREE MONTHS. THUS WE MIGHT EXPECT TO SEE SOME RESIDUAL ATMOSPHERIC RESPONSE TO THE WEAKENING EL NINO CONDITIONS CONTINUING INTO THE SPRING SEASON BUT LITTLE OR NO INFLUENCE IS ANTICIPATED AFTER THAT. EPISODES OF HEAVY PRECIPITATION IN CALIFORNIA AND THE INTERIOR SOUTHWEST THAT HAVE OCCURRED SINCE EARLY JANUARY ARE THE RESULT OF UNUSUAL CIRCULATION PATTERNS IN THE NORTH PACIFIC OCEAN THAT ARE NOT TYPICAL OF EL NINOS. THE SUBTROPCIAL WESTERLIES OVER MUCH OF THE NORTHERN HEMISPHERE ARE PREDICTED TO BE SOMEWHAT STRONGER THAN NORMAL FOR THE NEXT TWO WEEKS... MAINLY AS A RESULT OF STRONG BLOCKING OVER THE NORTH ATLANTIC AND TO A LESSER DEGREE OVER THE NORTHEASTERN GuLF OF ALASKA. THE CLIMATE OVER THE NORTH AMERICAN SECTOR FOR THE NEXT FEW MONTHS WILL PROBABLY BE INFLUENCED MORE BY THE INTERNAL DYNAMICS OF THE MID-LATITUDE CIRCULATION AND POSSIBLY SOME CONTINUING MADDEN-JULIAN OSCILLATION (MJO) ACTIVITY OVER THE WESTERN AND CENTRAL EQUATORIAL PACIFIC THAN IT WILL BY THE WEAKENING EL NINO. . . . . . . . . ALTHOUGH SOME EL NINO-RELATED INFLUENCE ON U.S. CLIMATE IS POSSIBLE FOR THE EARLY SPRING... EL NINO IMPACTS IN THE LONG-LEAD OUTLOOKS FOR SEASONS BEYOND MAM 2005 ARE EXPECTED TO BE NEGLIGIBLE. FOR LEAD TIMES BEYOND MAM 2005 THE OUTLOOK PRIMARILY REFLECTS LONG TERM TEMPERATURE AND PRECIPITATION TRENDS... WITH SOME CONSIDERATION OF INDICATIONS FROM CLIMATE MODELS THROUGH JJA 2005. . . . . . . . . THE OUTLOOK FOR MAM 2005 THROUGH JJA 2005 IS BASED ON THE CFS MODEL FROM NCEP AND THE MULTI-MODEL ENSEMBLE FROM THE IRI... THE STATISTICAL TOOLS CCA... OCN... SMLR... AND FOR MAM 2005 ONLY... TREND ADJUSTED ENSO COMPOSITES FROM CPC. THE CONSTRUCTED ANALOG SOIL MOISTURE (CAS) MODEL WAS ALSO CONSIDERED FOR THE FIRST SEASON. MODEL FORECASTS BECAME WEAK AND WERE FILTERED OUT BY THE SKILL MASKS IN MOST LOCATIONS BY THE SUMMER FORECAST... SO OCN IS THE PRIMARY TOOL USED FOR JJA 2005 TO MAM 2006. IN GENERAL CHANGES FROM THE OUTLOOK ISSUED ONE MONTH AGO ARE SMALL. THERE IS GOOD AGREEMENT AMONG ALL OF THE DYNAMICAL AND STATISTICAL MODELS FOR THE MAM 2005 FORECAST ON ABOVE MEDIAN PRECIPITATION IN PARTS OF THE SOUTHWEST U.S. ESPECIALLY IN ARIZONA AND NEW MEXICO... WITH SOME CONSENSUS FOR EXTENDING THIS AREA WESTWARD TO SOUTHERN CALIFORNIA AND EASTWARD THROUGH THE SOUTHERN GREAT PLAINS. TOOLS DIFFER ON THE PRECIPITATION IN THE EASTERN GULF REGION AND FLORIDA. THE CFS AND MOST MODELS SUGGEST DRY CONDITIONS FOR FLORIDA... IN OPPOSITION TO MOST STATISTICAL TOOLS AND TO ENSO COMPOSITES. THE CFS... MOST OTHER MODELS... AND STATISTICAL TOOLS ALL PREDICT ABOVE NORMAL TEMPERATURES THROUGH MOST OF THE WEST... WITH MIXED SIGNALS EAST OF THE ROCKIES EXCEPT IN THE SOUTHERN AND CENTRAL GREAT PLAINS. A SMALL AREA OF PREDICTED BELOW NORMAL TEMPERATURES THAT HAD BEEN INDICATED FOR THE NORTH-CENTRAL STATES ON THE MAM 2005 FORECAST ISSUED LAST MONTH WAS REMOVED THIS MONTH BECAUSE MOST OF THE MODELS ARE CURRENTLY INDICATING ABOVE NORMAL TEMPERATURES THERE... IN OPPOSITION TO THE CCA AND OCN STATISTICAL TOOLS THAT WERE WEAKLY INDICATING BELOW NORMAL TEMPERATURES. THE CAS TOOL ALSO FAVORS BELOW NORMAL TEMPERATURES OVER MUCH OF THE SOUTH-CENTRAL STATES AND ABOVE NORMAL TEMPERATURES WITH BELOW MEDIAN PRECIPITATION OVER THE PACIFIC NORTHWEST. THE PROBABILIES FOR ABOVE NORMAL TEMPERATURES OVER THE SOUTHWEST ARE SOMEWHAT DIMINISHED FROM WHAT TRENDS ALONE WOULD INDICATE DUE TO THE EXPECTATION THAT RELATIVELY WET CONDITIONS WILL CONTINUE THERE THROUGH THE FIRST HALF OR SO OF SPRING. FOR AMJ 2005 AND BEYOND THE FORECASTS REFLECT MAINLY TRENDS TOWARDS WARMER THAN NORMAL TEMPERATURES OVER MUCH OF THE WEST IN THE LATE SPRING... AND CONTINUING OVER THOSE REGIONS AS WELL AS INCLUDING THE SOUTHEASTERN U.S. IN SUMMER. SMALL AREAS OF BELOW NORMAL TEMPERATURE WERE FORECAST OVER THE NORTH-CENTRAL STATES FOR MJJ AND JJA 2005 ON THE BASIS OF CCA WITH SOME SUPPORT FROM SMLR. ABOVE NORMAL TEMPERATURES WERE FAVORED IN SOUTH FLORIDA AND ARE LIKELY TO CONTINUE OVER THE SOUTHWESTERN U.S. IN THE FALL... BUT WITH DIMINISHED CONFIDENCE IN LATE FALL AND EARLY WINTER. THE AREA OF PREDICTED ABOVE NORMAL TEMPERATURES OVER THE WEST EXPANDS AGAIN BY MAM 2006 REFLECTING INCREASED RELIABILITY OF LONG-TERM TRENDS AT THAT SEASON. IN THE ABSENCE OF ANY OTHER SIGNALS FOR DJF 2005-06 AND JFM 2006... A WEAK PREFERENCE FOR RELATIVE WARMTH IS SHOWN FOR PARTS OF THE NORTHEASTERN AND MIDWESTERN U.S. BASED ON LONG-TERM TRENDS. . . . . . . . . FROM AMJ 2005 THROUGH MAM 2005 THE OUTLOOK REFLECTS PRECIPITATION TRENDS... WHICH ARE GENERALLY MODEST. MANY SEASONS WERE NOT CONSIDERED TO HAVE ANY RELIABLE SIGNALS AND SEVERAL OF THE PRECIPITATION MAPS HAVE ALL EC. . . . . . . . . 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 CURRENT OCEANIC AND ATMOSPHERIC CONDITIONS INDICATE THAT THE WEAK EL NINO CONDITIONS THAT NOW EXIST IN THE CENTRAL TROPICAL PACIFIC ARE BEGINNING TO FADE BACK TO NEUTRAL CONDITIONS. THE NOAA DEFINITION OF EL NINO CONDITIONS REQUIRES THAT 3-MONTH RUNNING MEAN SST ANOMALIES IN THE NINO 3.4 REGION - BETWEEN 120W TO 170W AND WITHIN 5 DEGREES OF THE EQUATOR - EXCEED +0.5 DEGREES CELSIUS. THIS HAS BEEN THE CASE SINCE JAS 2004. THE MOST RECENT TWO WEEKLY MEANS SHOW THAT THE AREA OF SSTS THAT ARE MORE THAN 1 C ABOVE NORMAL CENTERED NEAR THE EQUATOR AND THE DATE LINE HAS DIMINISHED IN SIZE. SSTS ALONG THE EQUATOR EAST OF 160W AVERAGE ABOUT 0.5 C ABOVE NORMAL... EXCEPT JUST OFF THE SOUTH AMERICAN COAST WHERE SSTS NOW AVERAGE A LITTLE MORE THAN 0.5 C BELOW NORMAL. NEVERTHELESS... FOR THE FIRST TIME IN RECENT MONTHS... ENHANCED CONVECTION HAS EXTENDED SOMEWHAT EAST OF THE DATE LINE IN THE CENTRAL EQUATORIAL PACIFIC... WHICH MAY FAVOR ATMOSPHERIC RESPONSES CONSISTENT WITH COMPOSITES OF PAST CENTRAL PACIFIC WARM EVENTS FOR THE NEXT FEW WEEKS. . . . . . . . . PROGNOSTIC DISCUSSION OF SST FORECASTS ENSEMBLE PREDICTIONS FROM THE NEW CFS MODEL PREDICT THAT SEASONAL MEAN NINO 3.4 SST ANOMALIES WILL DECREASE FROM THE MOST RECENT THREE MONTH AVERAGE OF ABOUT +0.6 C TO ABOUT +0.4 C DURING MAM AND TO NEAR OR SLIGHTLY BELOW NORMAL FOR MJJ 2005 AND BEYOND. STATISTICAL PREDICTIONS FROM CCA... CA... AND THE MARKOV MODEL KEEP NINO 3.4 SST ANOMALIES ABOVE ZERO... WITH CCA THE WARMEST TOOL... PREDICTING SSTS TO INCREASE SLIGHTLY TO JUST OVER 1 DEG C BY FALL 2005. THE CA TOOL PREDICTS SST ANOMALIES TO DECREASE SLOWLY TO +0.1 C BY EARLY SUMMER.... WHILE THE MARKOV TOOL GRADUALLY INCREASES THEM TO JUST UNDER +1 C BY LATE NEXT FALL. A SKILL-WEIGHTED CONSOLIDATION OF DYNAMICAL AND STATISTICAL NINO 3.4 SST FORECASTS INDICATES THE NINO 3.4 SST ANOMALIES WILL DRIFT SLOWLY LOWER THROUGH THE LATE SPRING TO ABOUT +0.3 C BY AMJ AND MJJ 2005 AND THEN GRADUALLY INCREASE AGAIN FOR THE REMAINDER OF THE YEAR TO VALUES JUST ABOVE THE WEAK EL NINO THRESHOLD. SINCE WE ARE APPROACHING THE SPRING BARRIER AFTER WHICH A PRIORI SKILL IN PREDICTIONS OF NINO 3.4 SST DIMINSH RAPIDLY... FORECAST INDICATIONS ARE CONSIDERED RATHER UNRELIABLE AFTER THE FIRST FEW SEASONS AND THE STATUS OF ENSO WAS NOT A FACTOR IN FORMULATING THE SEASONAL FORECASTS BEYOND SPRING 2005. PROGNOSTIC TOOLS USED FOR U.S. TEMPERATURE AND PRECIPITATION OUTLOOK THE OUTLOOK FOR MAM 2005 THROUGH JJA 2005 IS BASED ON THE CFS MODEL FROM NCEP... THE MULTI-MODEL ENSEMBLE FROM IRI... AND THE STATISTICAL TOOLS CCA... SMLR AND OCN. CAS AND TREND-ADJUSTED EL NINO COMPOSITES WERE ALSO CONSIDERED FOR MAM 2005. OCN IS THE PRIMARY TOOL USED FOR JAS 2005 THROUGH MAM 2006. CHANGES FROM THE OUTLOOK ISSUED ONE MONTH AGO ARE MINOR. . . . . . . . . PROGNOSTIC DISCUSSION OF OUTLOOKS - MAM 2005 TO MAM 2006 TEMPERATURE: FOR MAM THROUGH MJJ 2005 THE FORECAST TOOLS VERY CONSISTENTLY PREDICT AN ENHANCED LIKELIHOOD OF ABOVE NORMAL TEMPERATURES IN THE WESTERN U.S AND ALASKA. THE CHANCES OF ABOVE NORMAL TEMPERATURES FOR MAM 2005 OVER MUCH OF THE SOUTHWESTERN U.S. AND THE SOUTHERN GREAT BASIN WERE REDUCED FROM PREVIOUS OUTLOOKS FOR CONSISTENCY WITH FORECASTS FOR ABOVE MEDIAN PRECIPITATION AMOUNTS OVER MUCH OF THE REGION... WHICH WOULD LEAD TO A COOL START TO THE SEASON IN THOSE PORTIONS OF THE REGION THAT EXPERIENCE EPISODES OF PRECIPITATION AND ABNORMALLY WET GROUND. ENHANCED LIKELIHOOD OF BELOW NORMAL TEMPERATURES IS PREDICTED FOR MAM AND AMJ 2005 IN THE SOUTHERN GREAT PLAINS ON THE BASIS OF NEARLY ALL TOOLS. CCA AND SMLR SUGGEST THAT SMALL AREAS OF THE NORTH-CENTRAL STATES MAY EXPERIENCE BELOW NORMAL TEMPERATURES DURING MJJ AND JJA 2005. OCN GIVES STRONG INDICATIONS FOR ABOVE NORMAL TEMPERATURES FROM SPRING THROUGH SUMMER 2005 AND AGAIN BEGINNING IN WINTER 2005-06 FOR ALASKA. THERE IS ALSO SUPPORT FROM MANY OF THE MODELS FOR THE WARMTH EXPECTED THERE IN THE NEXT FEW SEASONS. LONG TERM TRENDS AS REFLECTED IN THE OCN TOOL ARE THE BASIS FOR THE ABOVE NORMAL TEMPERATURES PREDICTED OVER THE SOUTHWEST DURING ALL THE SEASONS AND FOR DJF 2005-06 AND JFM 2006 OVER PARTS OF THE MIDWEST AND NORTHEAST. . . . . . . . . PRECIPITATION: TOOLS ARE IN GOOD AGREEMENT ON THE MAIN FEATURES OF THE FORECAST FOR MAM 2005... INCLUDING AN ENHANCED LIKELIHOOD OF ABOVE-MEDIAN PRECIPITATON FROM CALIFORNIA ACROSS THE SOUTHWEST TO TEXAS... POSSIBLY EXTENDING NORTHEASTWARD TO THE MIDDLE MISSISSIPPI AND LOWER OHIO VALLEYS. MOST OF THE MODELS AND CAS ARE INDICATING THAT DRY CONDITIONS ARE LIKELY TO CONTINUE OVER THE NORTHWESTERN U.S. ... AND THIS PATTERN IS CONSISTENT WITH THE EXPECTED WETNESS OVER THE SOUTHWEST. THERE ARE MIXED SIGNALS FOR PRECIPITATION ALONG THE EASTERN GULF COAST INTO FLORIDA... WITH THE CFS AND CONSENSUS OF OTHER CLIMATE MODELS INDICATING DRY CONDITIONS AND MOST STATISTICAL TOOLS AND EL NINO COMPOSITES CONTINUING TO SUGGEST A SLIGHTLY ENHANCED CHANCE OF ABOVE MEDIAN PRECIPITATION. WITH NO CONSENSUS FOR THE PRECIPITATION FORECAST OVER THE EASTERN GULF... THIS AREA HAS BEEN LEFT AS EC. FROM AMJ 2005 THROUGH MAM 2006... MANY OF THE FORECAST MAPS ARE GIVEN ALL EC DUE TO THE LACK OF ANY SIGNIFICANT OR CONSISTENT FORECAST SIGNALS. ALTHOUGH AN AREA OF ABOVE MEDIAN PRECIPITATION MIGHT BE EXPECTED SOMEWHERE IN THE GREAT PLAINS OR MIDWEST DURING THE LATE SPRING AND EARLY SUMMER SEASONS CONSISTENT WITH THE EXPECTED TEMPERATURE PATTERNSS... IT WOULD BE LARGELY CONVECTIVE AND HARD TO PREDICT... AND IS NOT SHOWN BY ANY OF THE STATISTICAL TOOLS EXCEPT CAS. ALSO... THE FORECAST SIGNALS FROM THE MODELS FOR THE MOST PART DID NOT PASS THROUGH THEIR SKILL MASKS. THUS THE MAPS FOR THESE SEASONS HAVE BEEN LEFT WITH ALL EC. OCN... CCA AND SMLR GIVE MAINLY WEAK BUT CONSISTENT INDICATIONS FOR AN ENHANCED LIKELIHOOD OF DRYNESS IN THE NORTHWEST FOR JJA THROUGH ASO 2005. CONSISTENT WITH RECENT TRENDS IN TROPICAL ACTIVITY IN THE ATLANTIC BASIN... OCN SHOWS INCREASED ODDS OF ABOVE MEDIAN PRECIPITATION AMOUNTS IN FLORIDA AND PARTS OF THE SOUTHEAST FOR ASO AND SON 2005... AND ALSO HAS AN ENHANCED PROBABILITY OF RLEATIVELY WET CONDITIONS IN THE SOUTH CENTRAL U.S. FROM OND 2005 TO DJF 2005-06. OTHER THAN IN THESE LIMITED AREAS... THERE WERE NO RELIABLE OR SIGNIFICANT SIGNALS FOR THE PRECIPITATION FORECASTS. NOTE - AREAS OF UNCERTAINTY THAT FORMERLY WERE LABELED CL (CLIMATOLOGICAL PROBABILITIES) ARE NOW LABELED EC (EQUAL CHANCES). . . . . . . . . FORECASTER: A. J. WAGNER 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 MARCH 17 2005. 1971-2000 BASE PERIOD MEANS WERE IMPLEMENTED EFFECTIVE WITH THE MAY 17 2001 FORECAST RELEASE. $$