PROGNOSTIC DISCUSSION FOR LONG-LEAD SEASONAL OUTLOOKS NWS CLIMATE PREDICTION CENTER CAMP SPRINGS MD 830 AM EST THU DEC 15 2005 NON-TECHNICAL 0.5 MONTH LEAD FORECAST SUMMARY . . . . . . . . THE MAIN FACTORS WHICH USUALLY INFLUENCE SEASONAL CLIMATE INCLUDE 1) EL NINO AND LA NINA – WHICH TOGETHER MAKE UP EL NINO/SOUTHERN OSCILLATION OR ENSO - 2) TRENDS – THE DIFFERENCE BETWEEN THE MOST RECENT 10 OR 15 YEAR MEAN OF TEMPERATURE OR PRECIPITATION FOR A GIVEN LOCATION AND TIME OF YEAR AND THE 30- YEAR CLIMATOLOGY PERIOD (CURRENTLY 1971-2000) - 3) TROPICAL 30-60-DAY OSCILLATION- WHICH MAY AFFECT CLIMATE VARIABILITY WITHIN A SEASON - 4) THE NORTH ATLANTIC OSCILLATION - OR NAO - AND 5) PERSISTENTLY DRY OR WET SOILS IN THE SUMMER AND SNOW AND ICE COVER ANOMALIES IN THE WINTER. SST ANOMALIES IN THE EASTERN EQUATORIAL PACIFIC OCEAN HAVE BECOME INCREASINGLY NEGATIVE IN RECENT WEEKS... WHILE SSTS ALONG THE EQUATOR WEST OF THE DATELINE REMAIN SLIGHTLY ABOVE NORMAL. THESE SSTS... TOGETHER WITH ATMOSPHERIC INDICATORS SUGGEST THAT ENSO... WHICH IS CURRENTLY NEUTRAL... IS TRENDING TOWARD WEAK LA NINA CONDITIONS. MOST SST PREDICTION TOOLS SUGGEST ANOMALIES ARE CURRENTLY NEAR THEIR MINIMUM VALUES AND WILL RETURN TOWARD NORMAL IN THE SPRING. AT THIS TIME IT IS HARD TO TELL WHETHER ENSO WILL STAY NEUTRAL OR SLIP INTO A WEAK LA NINA CLASSIFICATION. A CONSOLIDATION FORECAST OF THE VARIOUS SST PREDICTION TOOLS FAVORS A NEUTRAL CLASSIFICATION. BOTH DYNAMICAL AND STATISTICAL CLIMATE PREDICTION TOOLS INDICATE THAT... IN EITHER CASE... THE PACIFIC IS CLOSE ENOUGH TO LA NINA CONDITIONS TO IMPACT THE CLIMATE FOR JFM 2006. HOWEVER... THE RELIABILITY OF ANTICIPATED IMPACTS IS LOWER THAN WOULD BE EXPECTED IN A MODERATE OR STRONG LA NINA EVENT. TROPICAL 30-60-DAY OSCILLATIONS ARE CURRENTLY WEAK AND ARE EXPECTED TO HAVE LITTLE OR NO IMPACT ON THE CLIMATE IN THE NEAR-TERM. THE NAO PHASE HAS AVERAGED STRONGLY NEGATIVE SO FAR THIS SEASON... WHICH IS NORMALLY ASSOCIATED WITH BELOW NORMAL TEMPERATURES IN THE EASTERN HALF OF THE CONUS. ALTHOUGH THE NAO PHASE IS NOT WELL PREDICTED ON SEASONAL TIMESCALES... THERE IS A SLIGHT AMOUNT OF PERSISTENCE IN THE INDEX... INCREASING THE LIKELIHOOD OF COLD WEATHER INTERVALS IN THE NORTH CENTRAL AND EASTERN U.S. IN THE COMING SEASON. SEVERAL CLIMATE MODELS HAVE ALSO HINTED AT CIRCULATION PATTERNS WHICH FAVOR COLD TEMPERATURES IN THE EAST... AND THUS THE TEMPERATURE OUTLOOK FOR JFM WAS REVISED OVER THE NORTH CENTRAL U.S. TO REFLECT A HIGHER FREQUENCY OF BELOW NORMAL TEMPERATURES THAN INDICATED IN LAST MONTHS OUTLOOK. SIMILAR REVISIONS WERE MADE IN THE PACIFIC NORTHWEST AND ALASKA TO ACCOUNT FOR THE INCREASED FREQUENCY OF BELOW NORMAL TEMPERATURES ASSOCIATED WITH LA NINA. BECAUSE ENSO IS EXPECTED TO BE JUST SHY OF LA NINA CLASSIFICATION... AND SKILL OF THE NAO PREDICTION IS LOW... IT IS UNCLEAR WHETHER THERE IS SUFFICIENT PREDICTABILITY IN THESE SIGNALS TO OVERCOME THE RECENT WARMING TRENDS... SO THE FORECAST INDICATES EQUAL CHANCES FOR THE THREE TEMPERATURE CATEGORIES... ABOVE - NEAR - OR BELOW NORMAL... IN THESE AREAS. THE TEMPERATURE OUTLOOK FOR JANUARY-FEBRUARY-MARCH (JFM) 2006 CALLS FOR WARMER- THAN-NORMAL CONDITIONS IN THE FLORIDA PENINSULA AND IN THE SOUTHERN AND CENTRAL U.S. FROM JUST EAST OF THE MISSISSIPPI WESTWARD TO THE PACIFIC COAST... EXCEPT FOR SOME AREAS ALONG THE IMMEDIATE COAST IN SOUTHERN CALIFORNIA. ELSEWHERE TEMPERATURES HAVE EQUAL CHANCES OF WARMER-THAN... COOLER-THAN OR NEAR- NORMAL TEMPERATURES THIS JFM. ABOVE NORMAL TEMPERATURES ARE ANTICIPATED IN HAWAII. THE PRECIPITATION OUTLOOK FOR JFM CALLS FOR DRIER THAN NORMAL CONDITIONS OVER MUCH OF THE SOUTHERN THIRD OF THE CONUS. THIS IS A CONSISTENT RESPONSE TO WEAK LA NINA CONDITIONS AND IS PRESENT TO SOME DEGREE AMONG MOST SEASONAL FORECASTING TOOLS... PARTICULARLY THE DYNAMICAL MODELS. ABOVE MEDIAN PRECIPITATION IS ANTICIPATED IN THE ALASKAN PANHANDLE... AS SUGGESTED BY THE CFS CLIMATE MODEL... AND ALSO IN HAWAII. . . . . . . . . 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 THE OCEANIC AND ATMOSPHERIC INDICATORS IN THE TROPICAL PACIFIC OCEAN CURRENTLY FAVOR A NEUTRAL ENSO CLASSIFICATION. SSTS ALONG THE EQUATOR IN THE EASTERN PACIFIC ARE MORE THAN .5 DEG C BELOW NORMAL FROM ABOUT 150W TO THE SOUTH AMERICAN COAST... WITH SOME REGIONS REACHING ANOMALIES OF CLOSE TO -2 C. SSTS FROM 150 W TO THE DATELINE ARE WITHIN .5 DEG C OF NORMAL WHILE SSTS ALONG THE EQUATOR WEST OF THE DATELINE AVERAGE JUST OVER .5 DEG C ABOVE NORMAL. BELOW NORMAL OCEAN TEMPERATURES IN THE EASTERN PACIFIC EXTEND FROM THE SURFACE TO OVER 150 METERS DEPTH. ABOVE NORMAL OCEAN TEMPERATURES IN THE WESTERN PACIFIC ALSO EXTEND TO DEPTHS OF 150 METERS OR MORE... SO THE PATTERN OF SSTS SHOULD PERSIST THROUGH AT LEAST THE NEXT MONTH. MJO ACTIVITY IS CURRENTLY WEAK. SSTS REMAIN ABOVE NORMAL IN MUCH OF THE TROPICAL AND SUBTROPICAL ATLANTIC... ALTHOUGH ANOMALIES HAVE DECREASED FROM THEIR PEAK VALUES EARLIER IN THE YEAR. SSTS IN THE GULF OF ALASKA HAVE RETURNED TO NORMAL VALUES AFTER HAVING BEEN MUCH ABOVE NORMAL IN THE PAST FEW SEASONS. . . . . . . . . PROGNOSTIC DISCUSSION OF SST FORECASTS THE CONSENSUS OF SEVERAL MODELS USED AT CPC SUGGEST THAT SST ANOMALIES IN THE NINO 3.4 REGION (BETWEEN 5N AND 5S AND 170W TO 120W) ARE CLOSE TO THEIR MINIMUM VALUES. THE 3-MONTH SEASONAL MEAN NINO 3.4 SST ANOMALIES ARE FORECAST TO BE LOWEST IN DJF 2005-06... AT AROUND -.4 DEG C... INCREASING TO WITHIN .1 DEG C BY MAM 2006 AND REMAINING VERY CLOSE TO ZERO FOR THE REMAINDER OF THE SPRING AND SUMMER MONTHS. THE SKILL OF THE FORECASTS BECOMES NEGLIGIBLE BY LATE IN THE YEAR AS NINO 3.4 SST ANOMALIES ARE FORECAST TO EDGE INTO POSITIVE VALUES. THE CONSENSUS SST FORECAST SUGGESTS THAT THIS WINTER WILL BEST BE CLASSIFIED AS NEUTRAL ENSO... ALTHOUGH CLOSE TO THRESHOLD VALUES FOR A MINIMAL LA NINA. PROGNOSTIC TOOLS USED FOR U.S. TEMPERATURE AND PRECIPITATION OUTLOOKS THE GRADIENT OF SSTS IN THE EQUATORIAL PACIFIC... BELOW NORMAL IN THE EAST WITH NEAR TO ABOVE NORMAL SSTS IN THE CENTRAL AND WESTERN PACIFIC... IS EXPECTED TO HELP MAINTAIN STRONGER THAN AVERAGE LOW LEVEL EASTERLIES IN THE CENTRAL EQUATORIAL PACIFIC. SURFACE PRESSURE PATTERNS OVER THE CENTRAL AND WESTERN PACIFIC HAVE PUSHED THE 3-MONTH MEAN SOI TO ITS HIGHEST VALUES SINCE 2001. CLIMATE MODELS SUGGEST THAT THE ATMOSPHERIC RESPONSE TO THESE CONDITION IS SIMILAR TO THAT OF A WEAK LA NINA. THE MODELS HAVE DONE REASONABLY WELL IN REPRODUCING THE CIRCULATION PATTERNS OBSERVED THUS FAR THIS SEASON... AND THEREFORE THE CLIMATE MODELS ARE GIVEN MORE WEIGHT IN OUTLOOKS FOR JFM THROUGH FMA 2006 THAN THEY WOULD FROM LONG-TERM SKILL CONSIDERATIONS ALONE. THE OUTLOOK FOR JFM 2006 THROUGH FMA 2006 IS PRIMARILY BASED THE CLIMATE MODELS ... A MULTI-MODEL ENSEMBLE FROM IRI... THE CFS... AND CDC TOOLS BASED ON CLIMATE MODELS. SOME CONSIDERATION IS ALSO GIVEN TO THE STATISTICAL TOOLS... INCLUDING CCA... ECCA... SMLR AND OCN. FORECASTS FROM MAM THROUGH JJA 2006 REFLECT THE CONSOLIDATED TEMPERATURE PRODUCT... WHICH PRODUCES A SKILL WEIGHTED MIX OF CFS... CCA... SMLR... AND OCN. THE OUTLOOK FOR JAS 2006 THROUGH JFM 2007 ARE BASED ON A CONSOLIDATION OF CCA... SMLR... AND OCN... ALTHOUGH OCN IS THE PRIMARY INFLUENCE BEYOND JAS. . . . . . . . . PROGNOSTIC DISCUSSION OF OUTLOOKS - JFM 2006 TO JFM 2007 TEMPERATURE: TEMPERATURE PROBABILITIES OVER THE NORTHERN U.S. FROM THE GREAT LAKES WESTWARD TO THE PACIFIC NORTHWEST AND ALSO IN ALASKA FOR JFM 2006 HAVE BEEN REVISED FROM THE CORRESPONDING OUTLOOK ISSUED LAST MONTH. THIS CHANGE REFLECTS THE ELEVATED CHANCES FOR BELOW NORMAL TEMPERATURES ASSOCIATED WITH THE LA NINA-LIKE ATMOSPHERIC CONDITIONS PREDICTED BY THE DYNAMIC MODELS... AS WELL AS THE POSSIBILITY OF A PERSISTENT NEGATIVE NAO PHASE. THE INCREASED CHANCES OF BELOW NORMAL TEMPERATURES LARGELY COUNTERACTS THE INFLUENCE OF RECENT WARMING TRENDS AND BRINGS TEMPERATURE PROBABILITIES IN THESE AREAS IN LINE WITH 1971-2000 CLIMATOLOGY. THE ENHANCED CHANCES OF ABOVE NORMAL TEMPERATURES PREDICTED OVER MUCH OF THE SOUTHERN AND CENTRAL CONUS ARE MAINLY DUE TO TRENDS... WITH SOME ENHANCEMENTS IN CONFIDENCE DUE TO SUPPORT FROM THE CFS AND OTHER MODELS IN THE SOUTHWEST INTO WESTERN TEXAS. THE OUTLOOKS FOR FMA 2006 AND BEYOND ARE QUITE SIMILAR TO THOSE ISSUED LAST MONTH... WITH SOME ADJUSTMENTS IN FMA AND MAM TO REFLECT THE INCREASED EMPHASIS PLACED IN THE CFS AND OTHER CLIMATE MODELS. . . . . . . . . PRECIPITATION: THERE IS WIDE SPREAD CONSENSUS AMONG DYNAMICAL MODELS FOR BELOW MEDIAN PRECIPITATION OVER THE SOUTHERN THIRD OF THE CONUS FOR JFM 2006. CCA... ECCA AND SMLR FORECASTS ALSO SUPPORT THE FORECAST FOR BELOW MEDIAN PRECIPITATION OVER PORTIONS OF SOUTHERN U.S. THERE IS NO CLEAR CONSENSUS AMONG TOOLS FOR ABOVE MEDIAN PRECIPITATION IN THE CONUS. WHILE THE CFS MODEL FAVORS ABOVE MEDIAN PRECIPITATION IN THE AREAS USUALLY FAVORED DURING LA NINA WINTERS... THE IRI ENSEMBLES FAVOR DRY CONDITIONS OVER MANY OF THESE SAME AREAS. THERE IS GOOD MODEL CONSENSUS FOR ABOVE MEDIAN PRECIPITATION AMOUNTS FOR THE ALASKAN PANHANDLE IN JFM. MANY MODELS EXTEND THIS AREA OF ABOVE MEDIAN PRECIPTIATION INTO THE PACIFIC NORTHWEST... HOWEVER THEY ALSO SUGGEST A TIGHT NORTH-SOUTH GRADIENT BETWEEN WET AND DRY CONDITIONS ALONG THE WEST COAST AND... IN VIEW OF THE WEAK ENSO CONDITIONS... THE PACIFIC NORTHWEST IS KEPT UNDER EQUAL CHANCES. DYNAMICAL MODELS PERSIST THE DRY CONDITIONS IN PARTS OF THE SOUTHERN CONUS INTO SPRING... BUT WITH SSTS IN THE NINO 3.4 REGION RETURNING TO NORMAL... CONFIDENCE IN THE FORECAST GRADUALLY DIMINISHES. THE PRECIPITATION FORECAST FOR MAM 2006 AND BEYOND... WHERE DIFFERENT FROM EQUAL CHANCES... PRIMARILY REFLECTS PRECIPITATION TRENDS. . . . . . . . . FORECASTER: D. UNGER 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. CON - A FORECAST TOOL WHICH COMBINES THE CCA - THE OCN - THE SMLR AND A 15-MEMBER ENSEMBLE MEAN FROM THE CFS - USING THE KNOWN SKILL OF THE VARIOUS TOOLS TO FORM A WEIGHTED AVERAGE. THIS TOOL HELPS TO REDUCE THE UNCERTAINTY WHICH FORECASTERS CONFRONT WHEN THEY TRY TO SUBJECTIVELY COMBINE FORECAST TOOLS. CON HAS BEEN USED IN THE TEMPERATURE AND PRECIPITATION FORECASTS THIS TIME. VERIFICATION OF CON FOR FORECASTS FROM THE 1995-2005 PERIOD INDICATES THAT IT IMPROVES TEMPERATURE FORECASTS OVER THE CONUS. PRECIPITATION FORECASTS FROM CON HAVE NOT YET BEEN VERIFIED AND IT IS - THEREFORE - USED MUCH MORE CONSERVATIVELY THAN IT IS FOR TEMPERATURE. . . . . . . . . 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 JAN 19 2006. 1971-2000 BASE PERIOD MEANS WERE IMPLEMENTED EFFECTIVE WITH THE MAY 17 2001 FORECAST RELEASE. $$