PROGNOSTIC DISCUSSIONS FOR 6 TO 10 AND 8 TO 14 DAY OUTLOOKS CLIMATE PREDICTION CENTER NCEP NATIONAL WEATHER SERVICE WASHINGTON DC 3 PM EST TUE NOV 12 2002 6 TO 10 DAY OUTLOOK FOR NOV 18 - 22 2002 NOTE: THE MODEL THAT USED TO BE REFERRED TO AS THE MRF AND AVN IS NOW KNOWN AS THE GFS (GLOBAL FORECAST SYSTEM) MODEL. SEE GLOSSARY FOR DETAILS. . . . . . . . . MODEL COMPARISONS: AGAIN TODAY GOING INTO THE FORECAST 6-10 DAY PERIOD THE DAILY MODEL FORECASTS ALL SHOW A RATHER AMPLIFIED TROUGH SOMEWHERE BETWEEN THE MISSISSIPPI RIVER AND THE APPALACHIANS.. BUT DIFFER ON DETAILS OF AMPLITUDE... TILT AND PHASING OF SHORT WAVE ENERGY IN THE NORTHERN AND SOUTHERN STREAMS. THESE DIFFERENCES IN DETAILS COULD BE CRITICAL FOR TIMING OF PRECIPITATION BEFORE OR AT THE BEGINNING OF THE 6-10 DAY PERIOD... BUT OVERALL TODAY THE STORM IS INDICATED TO BE SOMEWHAT SLOWER AND MORE INTENSE THAN YESTERDAY. FOR THE 6-10 DAY PERIOD MODELS ARE IN GENERAL AGREEMENT WITH A TROUGH OVER THE EASTERN HALF OF THE U.S. AND THE ASSOCIATED NEGATIVE ANOMALY CENTERED NEAR THE GEORGIA COAST. ALL MODELS SHOW RIDGES WITH THREE ASSOCIATED POSITIVE ANOMALY CENTERS LOCATED NEAR OR OVER THE CENTRAL GREAT BASIN... SOUTHEAST OF THE CANADIAN MARITIMES.... AND IN THE VICINITY OF NORTHEASTERN HUDSON BAY. THE CENTER OF CYCLONIC ACTIVITY IN THE EASTERN PACIFIC IS PREDICTED TO REMAIN JUST SOUTH OF ALASKA... AND SOME MODELS SHOW A SEPARATE STRONG NEGATIVE ANOMALY CENTER OVER THE BEAUFORT SEA... BUT BOTH ARE PART OF A LARGE AREA OF BELOW NORMAL HEIGHTS AND STRONGLY CYCLONIC FLOW. MOST OF THE HIGH LATITUDE BLOCKING IS PREDICTED TO BE ON THE EASTERN HEMISPHERE SIDE OF THE POLE... EXCEPT FOR THE ABOVE MENTIONED POSITIVE ANOMALY CENTER OVER NORTHEASTERN HUDSON BAY. AS IS USUALLY THE CASE... THE DAVA AND THE ENSEMBLE MEAN SHOW THE LEAST AMPLIFIED PATTERNS WHILE YESTERDAYS 12Z AND 18Z HIGH RESOLUTION GFS RUNS ARE THE MOST AMPLIFIED. FORECAST CONFIDENCE IS ABOVE AVERAGE TODAY... 4 ON A SCALE FROM 1 TO 5 DUE TO GOOD MODEL AGREEMENT AND REASONABLY GOOD TELECONNECTIVITY FROM THE POSITIVE ANOMALY CENTER AT 35N/110W AND NEGATIVE ANOMALY OVER THE SOUTHEAST. THE OFFICIAL 500-HPA HEIGHT FORECAST FOR THE 6 TO 10 DAY PERIOD USES 50 PERCENT OF THE GFS ENSEMBLE MEAN CENTERED ON DAY 8... 40 PERCENT OF THE DAVA MODEL CENTERED ON DAY 8... AND 10 PERCENT OF THE ECMWF CENTERED ON DAY 6. THE 00Z GFS MODEL WAS NOT AVAILABLE TO THE BLEND AT FORECAST TIME... AND TODAYS ECMWF MODEL WAS NOT AVAILBABLE AT ALL. MODEL OF THE DAY: GFS ENSEMBLE THE TEMPERATURE PROG IS BASED MAINLY ON THE KLEIN... NEURAL NET AND FIRST GUESS GUIDANCE FROM THE OFFICIAL HEIGHT BLEND... MOS GUIDANCE FROM THE GFS ENSEMBLE MEMBERS...ANALOGS FROM THE OFFICIAL HEIGHT PROG...AND TELECONNECTIONS BASED ON THE POSITIVE HEIGHT CENTER AT 35N 110W. THE PRECIPITATION PROG IS BASED ON THE NEURAL NET SPECIFICATIONS FROM THE 500- HPA BLEND... ANALOGS ON THE OFFICIAL HEIGHT BLEND... THE BIAS CORRECTED AND CALIBRATED PRECIPITATION FROM THE GFS...AND TELECONNECTIONS BASED ON THE POSITIVE HEIGHT CENTER AT 37N 110W. . . . . . . . . 8 TO 14 DAY OUTLOOK FOR NOV 20 - 26 2002 MODEL COMPARISONS: FOR THE WEEK TWO PERIOD THE MODELS TODAY ARE OFFERING FOUR DIFFERENT SOLUTIONS... NONE OF WHICH CAN BE RULED OUT AS UNREASONABLE. THE ENSEMBLE MEAN AND THE 12Z GFS KEEP A WEAKENING TROUGH OVER THE SOUTHEAST... THE 00Z AND 18Z GFS RUNS SHOW A NEW TROUGH BREAKING THROUGH FROM BRITISH COLUMBIA SOUTHEASTWARD THROUGH THE ROCKIES... THE 06Z GFS SHOWS TROUGHING AND A NEGATIVE ANOMALY OVER THE NORTHEASTERN U.S. ... AND THE DAVA MODEL INDICATES THAT THE TROUGH WOULD ESSENTIALLY DISAPPEAR AND BE REPLACED BY ABOVE NORMAL HEIGHTS OVER THE ENTIRE CONUS AND SOUTHEASTERN TWO-THIRDS OF CANADA... EXCEPT FOR WEAK RESIDUAL NEGATIVE ANOMALIES NEAR THE GULF COAST. THE LATTER SOLUTION IS MORE IN KEEPING WITH PREFERRED MODAL DOWNSTREAM TELECONNECTIONS FROM NEGATIVE HEIGHT ANOMALIES CENTERED NEAR THE SOUTH COAST OF ALASKA. CONFIDENCE IN THE WEEK 2 FORECAST IS BELOW AVERAGE... 2 ON A SCALE FROM 1 TO 5. THE OFFICIAL 500-HPA HEIGHT FORECAST FOR THE 8 TO 14 DAY PERIOD USES 50 PERCENT OF THE GFS ENSEMBLE MEAN CENTERED ON DAY 11... 15 PERCENT OF TODAYS 00Z OPERATIONAL GFS CENTERED ON DAY 11... 25 PERCENT OF THE DAVA CENTERED ON DAY 11... AND 10 PERCENT OF YESTERDAYS 00Z GFS CENTERED ON DAY 10. THE TEMPERATURE PROG IS BASED MAINLY ON THE KLEIN... NEURAL NETWORK AND FIRST GUESS SPECIFICATIONS FROM THE OFFICIAL FORECAST 500-HPA BLEND AND ANALOGS FROM THE OFFICIAL HEIGHT BLEND. THE PRECIPITATION PROG IS BASED ON THE NEURAL NET SPECIFICATIONS FROM THE 500- HPA BLEND... ANALOGS FROM THE OFFICIAL FORECAST 500-HPA BLEND AND THE BIAS CORRECTED PRECIPITATION FROM THE OPERATIONAL GFS. THE CALIBRATED PRECIPITATION FROM THE OPERATIONAL GFS WAS NOT AVAILABLE FOR THE WEEK TWO PERIOD. FORECASTER: A. J. WAGNER . . . . . . . . NOTES: AUTOMATED FORECASTS ARE ISSUED ON SATURDAY AND SUNDAY. OTHERWISE - FORECASTS INCORPORATE FORECASTER INPUT. THE NOTATION FOR THE CATEGORICAL FORECAST INDICATED ON THE MAPS IS THE SAME AS THAT IN THE TABLES: A-ABOVE N-NEAR NORMAL B-BELOW IN THE SOUTHWEST AND OTHER CLIMATOLOGICALLY DRY REGIONS - THERE WILL BE A GREATER THAN 33.3% CHANCE OF NO PRECIPITATION AND OCCASIONALLY EVEN A NORMAL (I.E. MEDIAN) VALUE OF ZERO - ESPECIALLY DURING THE DRY SEASONS. IN SUCH CASES A FORECAST OF NEAR NORMAL IS EFFECTIVELY A FORECAST OF LITTLE OR NO PRECIPI- TATION. THE NARRATIVE DESCRIPTION OF THE FORECAST PATTERNS FOR TEMPERATURE AND PRECIP- ITATION FOR BOTH THE 6-10 OR 8-14 DAY PERIODS HAS BEEN DISCONTINUED. THE STATE TABLES FOR BOTH THE 6-10 AND 8-14 DAY PERIODS ARE NOW CONTAINED IN THIS MESSAGE ...AVAILABLE AS PMDMRD ON AWIPS. EFFECTIVE THURSDAY MAY 17 2001...THE CLIMATE PREDICTION CENTER HAS SWITCHED TO 1971-2000 BASE PERIOD MEANS FOR TEMPERATURE...PRECIPITATION...AND 500-HPA HEIGHTS AS REFERENCE IN THE CLIMATE OUTLOOKS. THE 1971-2000 BASE PERIOD MEANS HAVE REPLACED THE 1961-1990 BASE PERIOD MEANS. . . . . . . . . GLOSSARY AND DEFINITIONS:------------------------------------------------------ AC - ANOMALY CORRELATION - A MEASURE OF HOW WELL A MODEL FORECASTS THE HEIGHT OR HEIGHT ANOMALY FIELD OBTAINED BY CORRELATING THE IMPLIED GRADIENTS OF THE TWO ANOMALY PATTERNS BEING COMPARED. 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 STUDIED INCREASES IN SIZE. PERFECT ANALOGS TO THE ENTIRE NORTHERN HEMISPHERE SIMPLY DO NO EXIST - FOR PRACTICAL PURPOSES. THIS IS WHY SIMPLE NATURAL ANALOG FORECAST METHODS DO NOT WORK VERY WELL. ANOMALY - THE ARITHMETIC DIFFERENCE BETWEEN THE VALUE OF A VARIABLE AT A GIVEN PLACE AND TIME AND THE LONG-TERM AVERAGE OF THAT VARIABLE AT THAT PLACE AND TIME OF YEAR. AVN - THE RUN OF THE MRF MODEL INITIATED AT 12 UTC (AS OF 07/2002 THE NAME FOR ALL RUNS OF THE NCEP GLOBAL SPECTRAL MODEL). BLEND - A WEIGHTED AVERAGE OF 500 HPA HEIGHT FORECAST MAPS FROM SEVERAL MODELS. WEIGHTS ARE CURRENTLY ASSIGNED SUBJECTIVELY BY THE FORECASTER. THE SUM OF THE WEIGHTS MUST BE 1. WEIGHTS ARE APPLIED BY MULTIPLYING EACH 500 HPA MAP BY ITS WEIGHT AND ADDING ALL OF THE WEIGHTED MAPS TOGETHER TO MAKE THE OFFICIAL 500 HPA FORECAST. CONUS - CONTERMINOUS UNITED STATES. DAVA - DIVERGENT ANOMALY VORTICITY ADVECTION MODEL. THIS IS A BAROTROPIC MODEL WITH DIVERGENCE IN IT TO ALLOW MORE ACCURATE PREDICTION OF LONG WAVES THAN A STANDARD BAROTROPIC MODEL. REFERENCE: QIN J. AND H.M. VAN DEN DOOL - 1996: SIMPLE EXTENSIONS OF AN NWP MODEL. MON. WEA. REV. - VOL 124 - PP 277-287. EL NINO - THE WARM PHASE OF ENSO. ENSO - EL NINO/SOUTHERN OSCILLATION. FLOW PATTERN - THE PATTERN OF WIND INFERRED BY THE 500 HPA CONTOURS - THE WIND TENDS TO BLOW PARALLEL TO THE CONTOURS WITH LOW HEIGHT ON THE LEFT - IN THE NORTHERN HEMISPHERE - THE OPPOSITE IS TRUE IN THE SOUTHERN HEMISPHERE. WIND SPEED IS INVERSELY PROPORTIONAL TO THE SPACING BETWEEN THE CONTOURS. GFS - GLOBAL FORECAST SYSTEM. THIS REFERS TO ANY OF THE GLOBAL MODELS RUN AT NCEP FOUR TIMES A DAY THAT USED TO BE REFERRED TO AS THE MRF AND AVN MODELS. THE MODEL RUN INITIATED AT 00Z (OO GMT) IS THE ONE USED BY CPC IN ITS FORECASTS. 500 HPA HEIGHT IS THE HEIGHT - IN METERS - ABOVE MEAN SEA LEVEL - WHICH ABOUT HALF OF THE MASS OF THE ATMOSPHERE LIES ABOVE AND BELOW - AS MEASURED BY THE PRESSURE. UPPER AIR STORM SYSTEMS TEND TO BE STEERED IN THE DIRECTION OF THE WINDS AT 500 HPA. 500-HPA SYSTEMS CORRELATE STRONGLY WITH SURFACE WEATHER. HPA - HECTO-PASCALS. 1 HPA = 1 MILLIBAR. LA NINA - THE COLD PHASE OF ENSO. MERIDIONAL FLOW PATTERN - OCCURS WHEN 500 HPA CONTOURS EXHIBIT LARGE NORTHWARD AND SOUTHWARD EXCURSIONS WITH EXTENSIVE AREAS OF SOUTHERLY AND NORTHERLY FLOW. MODEL BIAS - THE DIFFERENCE BETWEEN THE MODEL CLIMATOLOGY AND THE OBSERVED CLIMATOLOGY - EXPRESSED AS BIAS = MODEL CLIMO - OBSERVED CLIMO. MODEL OF THE DAY - FOR 6-10 DAYS - IS THE MODEL WHOSE SOLUTION IS CONSIDERED TO BE MORE RELIABLE THAN USUAL - AND MAY BE GIVEN HIGHER THAN TYPICAL WEIGHT IN THE BLEND. NO MODEL OF THE DAY IS CHOSEN FOR 8-14 DAYS. MOS - MODEL OUTPUT STATISTICS - A STATISITCAL TOOL FOR SPECIFYING THE SURFACE TEMPERATURE (AND ITS ANOMALY) FROM MODEL FIELDS - CORRECTING AUTOMATICALLY FOR BOTH BIASES IN THE MODEL FIELDS AND THE SPECIFICATION METHOD. IT IS VALID AS LONG AS A GIVEN CONFIGURATION OF A MODEL IS NOT CHANGED OR MODIFIED. MRF - MEDIUM RANGE FORECAST MODEL (AS OF 07/2002 RENAMED THE AVN) MRF ENSEMBLE - A SET OF MRF (AVN) FORECASTS WHICH ARE ALL VALID AT THE SAME TIME BUT WHOSE STARTING CONDITIONS DIFFER BY SMALL AMOUNTS. THERE ARE CUR- RENTLY 25 MEMBERS IN THE MRF (AVN) ENSEMBLE. THE AVERAGE OF THESE IS THE MRF (AVN) ENSEMBLE MEAN. MJO - MADDEN-JULIAN OSCILLATION - ALSO CALLED TROPICAL INTRA-SEASONAL OSCILLA- TION - A SERIES OF WAVES WITH A PERIOD AVERAGING 50 DAYS THAT MOVES SLOWLY EASTWARD NEAR THE EQUATOR ALTERNATELY ENHANCING AND SUPRESSING PRECIPITATION. NAO - NORTH ATLANTIC OSCILLATION TELECONNECTION PATTERN. PNA - PACIFIC NORTH AMERICAN TELECONNECTION PATTERN. PROG - PROGNOSIS - OR FORECAST. RIDGE - A REGION OF UNUSUALLY HIGH 500 HPA HEIGHT. SHORT WAVES - RELATIVELY LOW-AMPLITUDE - FAST-MOVING DISTURBANCES OF THE 500 HPA FIELD. SOUTHERN STREAM - A FLOW PATTERN WITH UNUSUALLY STRONG FLOW ACROSS THE SOUTH- ERN U.S. - ACCOMPANIED BY UNUSUAL STORMINESS IN THE SOUTH AND SOUTHEAST. SPECIFICATIONS - KLEIN AND NEURAL NETWORK SPECIFICATIONS GIVE THE HISTORICAL RELATIONSHIP BETWEEN 500-HPA HEIGHT ANOMALIES AND SURFACE TEMPERATURE AND PRECIPITATION. KLEIN SPECIFICATIONS TEND TO EMPHASIZE REGIONAL TELECONNEC- TIONS WHILE THOSE FROM THE NEURAL NETWORK WORK FROM GLOBAL TELECONNECTIONS. . . . . . . . . TELECONNECTIONS GIVE THE HISTORICAL RELATIONSHIP BETWEEN THE 500-HPA HEIGHT AT A GIVEN POINT AND ALL OTHER POINTS ON A MAP FOR A GIVEN TIME OF YEAR. WE AVERAGE THE TOP/BOTTOM 10% OF DAILY MAPS FROM 1950-1999 FOR THE SAME TIME OF YEAR HAVING THE HIGHEST/LOWEST 500-HPA HEIGHT AT THE SPECIFIED POINT. TROUGH - A REGION OF UNUSUALLY LOW 500 HPA HEIGHT. UTC - UNIVERSAL TIME COORDINATED - SAME AS GREENWICH MEAN TIME (GMT). WESTERLY WIND - WIND BLOWING FROM WEST TO EAST. EASTERLY WIND - WIND BLOWING FROM EAST TO WEST. NORTHERLY WIND - WIND BLOWING FROM NORTH TO SOUTH SOUTHERLY WIND - WIND BLOWING FROM SOUTH TO NORTH. 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. ------------------------------------------------------------------------------- THE NEXT MONTHLY AND SEASONAL OUTLOOKS WILL BE RELEASED THURSDAY NOVEMBER 21 2002. 6 to 10 day Outlook Table STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN WASHINGTON A A OREGON A A NRN CALIF A N SRN CALIF A B IDAHO A N NEVADA A N W MONTANA A N E MONTANA A B WYOMING A B UTAH A B ARIZONA A B COLORADO A B NEW MEXICO A B N DAKOTA A B S DAKOTA A B NEBRASKA A B KANSAS A B OKLAHOMA A B N TEXAS N N S TEXAS N N W TEXAS A B MINNESOTA A N IOWA A B MISSOURI A B ARKANSAS A B LOUISIANA N N WISCONSIN A N ILLINOIS A B MISSISSIPPI N B MICHIGAN A N INDIANA A B OHIO A B KENTUCKY N B TENNESSEE N B ALABAMA B B NEW YORK A A VERMONT A A NEW HAMP A A MAINE A A MASS A A CONN A A RHODE IS A A PENN N N NEW JERSEY N A W VIRGINIA N N MARYLAND N A DELAWARE N A VIRGINIA N N N CAROLINA N N S CAROLINA B N GEORGIA B B FL PNHDL B B FL PENIN N N AK N SLOPE N N AK ALEUTIAN B B AK WESTERN B B AK INT BSN N N AK S INT N N AK SO COAST B A AK PNHDL A A 8 to 14 day Outlook Table STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN WASHINGTON A A OREGON A N NRN CALIF A N SRN CALIF A B IDAHO A N NEVADA A B W MONTANA A N E MONTANA A B WYOMING A B UTAH A B ARIZONA A B COLORADO A B NEW MEXICO A B N DAKOTA A N S DAKOTA A B NEBRASKA A B KANSAS A B OKLAHOMA A B N TEXAS A N S TEXAS N N W TEXAS A B MINNESOTA A A IOWA A A MISSOURI A N ARKANSAS A N LOUISIANA N A WISCONSIN A A ILLINOIS A N MISSISSIPPI N A MICHIGAN A N INDIANA A N OHIO A N KENTUCKY A A TENNESSEE A A ALABAMA N A NEW YORK A N VERMONT A N NEW HAMP A N MAINE A N MASS A N CONN A N RHODE IS A N PENN A N NEW JERSEY A N W VIRGINIA A A MARYLAND A N DELAWARE A N VIRGINIA A N N CAROLINA N N S CAROLINA N N GEORGIA N A FL PNHDL N A FL PENIN N N AK N SLOPE B N AK ALEUTIAN B N AK WESTERN B N AK INT BSN N N AK S INT N N AK SO COAST N A AK PNHDL A A LEGEND TEMPS WITH RESPECT TO NORMAL PCPN WITH RESPECT TO MEDIAN A - ABOVE N - NEAR NORMAL A - ABOVE N - NEAR MEDIAN B - BELOW B - BELOW THE FORECAST CLASSES REPRESENT AVERAGES FOR EACH STATE. NORMAL VALUES - WHICH MAY VARY WIDELY ACROSS SOME STATES - ARE AVAILABLE FROM YOUR LOCAL WEATHER SERVICE FORECAST OFFICE. FOR ADDITIONAL INFORMATION SEE MESSAGE FXUS06 - ON AFOS AS NFDPMDMRD. NNNN NNNN