PROGNOSTIC DISCUSSIONS FOR 6 TO 10 AND 8 TO 14 DAY OUTLOOKS CLIMATE PREDICTION CENTER NCEP NATIONAL WEATHER SERVICE WASHINGTON DC 3 PM EST WED JAN 8 2002 6 TO 10 DAY OUTLOOK FOR JAN 15 - 19 2002 . . . . . . . . NOTE: DUE TO NETWORK PROBLEMS... THE USUAL MANUAL 8 TO 14 DAY FORECASTS ARE NOT AVAILABLE AT THIS TIME. THE REGULAR 6 TO 10 FORECASTS ARE BEING ISSUED ALONG WITH THE AUTOMATED 8 TO 14 DAY FORECASTS. THE 6 TO 10 DAY FORECASTS WERE PREPARED BEFORE THE NETWORK PROBLEMS DEVELOPED. IF THE NETWORK IS REPAIRED BY AROUND 4 PM EST... THEN REVISED 8 TO 14 DAY FORECASTS WILL BE RELEASED. THE AUTOMATED 8 TO 14 DAY FORECASTS DO NOT RADICALLY DIFFER FROM THE MANUAL FORECASTS. MODEL COMPARISONS: MODELS ARE NOT IN NEARLY AS GOOD AGREEMENT AS EARLIER THIS WEEK... WITH THE NORTH PACIFIC-ALASKA RIDGE GENERALLY LESS AMPLIFIED THAN ON PREVIOUS FORECASTS... BUT THE ECMWF SHOWING A STRONGER RIDGE THAN OTHER MODELS. MODELS AGREE ON THE LARGE CYCLONIC VORTEX NORTH OF HUDSON BAY NEAR BAFFIN ISLAND... BUT DIFFER IN THE STRENGTH OF THE TROUGHING EXTENDING SOUTH AND SOUTHWESTWARD. THE MRF ENSEMBLE MEAN HAS STRONGER TROUGHING AND LOWER 500 HPA HEIGHTS OVER THE NORTHERN U.S. THAN THE MRF OPERATIONAL MODEL. THE ECMWF HAS POSITIVE HEIGHTS CENTERED NEAR WEST VIRGINA... IMPLYING A WARMER PATTERN FOR THE EAST AND MIDWEST. THE DAVA AND PRZ T62 HAVE WEAK POSITIVE HEIGHT ANOMALIES NEAR THE EAST COAST ALONG WITH BELOW NORMAL HEIGHTS CENTRAL AND WESTERN STATES... AND THIS IS DEEMED A REASONABLE SOLUTION. ABNORMAL COLD STILL APPEARS A SAFE BET FOR MUCH OF THE WEST AND PLAINS... WITH MOSTLY NEAR NORMAL TEMPERATURES ELSEWHERE. SOME WARMTH SHOULD LINGER ALONG THE GULF COAST DUE TO ABOVE NORMAL HEIGHTS THERE. . . . . . . . . CONFIDENCE IN TODAYS FORECAST IS RATED AS AVERAGE... 3 ON A 1-5 SCALE. THE OFFICIAL 500 HPA HEIGHT FORECAST FOR THE 6 TO 10 DAY PERIOD USES 50 PERCENT OF TODAYS MRF ENSEMBLE MEAN CENTERED ON DAY 8... 25 PERCENT OF TODAYS DAVA CENTERED ON DAY 8... 15 PERCENT OF TODAYS MRF CENTERED ON DAY 8......AND 10 PERCENT OF TODAYS ECMWF MODEL CENTERED ON DAY 7. . . . . . . . . MODEL OF THE DAY: DAVA THE TEMPERATURE PROG IS BASED PRIMARILY ON A THE MOS FROM THE MRF ENSEMBLE... WITH SOME TWEAKING BASED ON THE KLEIN FROM THE BLENDED 500 HPA PROG. THE PRECIPITATION PROG IS BASED MOSTLY ON THE ACCUMULATED MRF ENSEMBLE ANOMALIES AND THE BIAS-CORRECTED MRF CUMULATIVE TOTALS. 8 TO 14 DAY OUTLOOK FOR JAN 17 - 23 2002 . . . . . . . . TODAYS WEEK 2 MRF AND ENSEMBLE MEAN SHOW SOME IMPORTANT DIFFERENCES... MAKING THE FORECAST LESS CONFIDENT THAN EARLIER THIS WEEK. MODELS AGREE ON THE CONTINUED CYCLONIC VORTEX AT 500 HPA JUST NORTH OF HUDSON BAY... BUT THE MRF OPERATIONAL MODEL WANTS TO KEEP MUCH MORE OF THE PACIFIC RIDGE NORTH OF THE ALEUTIANS AND HIGHER HEIGHTS IN THE WESTERN U.S. THERE ARE MANY DIFFERENCES AMONG ENSEMBLE MODEL MEMBERS... BOTH THE MRF AND CANADIAN GBL... ON A POSSIBLE TROUGH EXTENDING SOUTHWESTWARD TOWARD THE SOUTHERN CALIFORNIA AND ARIZONA AREA. THE STRENGTH AND POSITION OF ANY SUCH TROUGH WILL MAKE A BIG DIFFERENCE FOR THE TEMPERATURE AND PRECIPITATION FORECAST. THE FINAL BLEND PRETTY MUCH DISPENSES WITH THIS FEATURE AND MAINTAINS A TROUGH OVER THE EASTERN THIRD OF THE U.S. CONFIDENCE IS THOUGHT TO BE BELOW AVERAGE TODAY...RATED 2 ON A SCALE OF 1-5. THE BLENDED 500 HPA HEIGHT PATTERN USES 70 PERCENT OF TODAYS MRF ENSEMBLE MEAN CENTERED ON DAY 11... 20 PERCENT OF TODAYS MRF MODEL CENTERED ON DAY 11... AND 10 PERCENT OF TODAYS DAVA MODEL CENTERED ON DAY 11. THE TEMPERATURE OUTLOOK IS BASED MAINLY ON A CONSENSUS OF THE KLEIN SPECIFICATIONS FROM THE MRF ENSEMBLE AND 850 HPA TEMPERATURES FROM THE MRF ENSEMBLE. THE PRECIPITATION FORECAST IS BASED PRIMARILY ON THE ACCUMULATED MRF ENSEMBLE OUTPUT AND THE MRF OUTPUT CORRECTED FOR RECENT BIASES. FORECASTER: D. LE COMTE . . . . . . . . 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 PRECIPITATION. THE NARRATIVE DESCRIPTION OF THE FORECAST PATTERNS FOR TEMPERATURE AND PRECIPITATION 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:----------------------------------------------------- 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. BLEND - A WEIGHTED AVERAGE OF FORECAST MODEL 500 HPA HEIGHT FORECAST MAPS. 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. CONUS - CONTINENTAL 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 NON-DIVERGENT 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. EASTERLY WIND - WIND BLOWING FROM EAST TO WEST. 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. WIND SPEED IS INVERSELY PROPORTIONAL TO THE SPACING BETWEEN THE CONTOURS. 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 LARGE SOUTHERLY AND NORTHERLY FLOW. MJO - MADDEN-JULIAN OSCILLATION - ALSO CALLED TROPICAL INTRA-SEASONAL OSCILLATION. 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. MRF - MEDIUM RANGE FORECAST MODEL. MRF ENSEMBLE - A SET OF MRF FORECASTS WHICH ARE ALL VALID AT THE SAME TIME BUT WHOSE STARTING CONDITIONS DIFFER BY SMALL AMOUNTS. THERE ARE CURRENTLY 25 MEMBERS IN THE MRF ENSEMBLE. THE AVERAGE OF THESE IS THE MRF ENSEMBLE MEAN. NAO - NORTH ATLANTIC OSCILLATION TELECONNECTION PATTERN. NORTHERLY WIND - WIND BLOWING FROM NORTH TO SOUTH 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. SOUTHERLY WIND - WIND BLOWING FROM SOUTH TO NORTH. SOUTHERN STREAM - A FLOW PATTERN WITH UNUSUALLY STRONG FLOW ACROSS THE SOUTHERN 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 TELECONNECTIONS 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. 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 ON THURSDAY JANUARY 17. 6 to 10 day Outlook Table STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN WASHINGTON B N OREGON B N NRN CALIF B B SRN CALIF B N IDAHO B A NEVADA B N W MONTANA B A E MONTANA B A WYOMING B A UTAH B N ARIZONA B N COLORADO B N NEW MEXICO N N N DAKOTA N A S DAKOTA B A NEBRASKA B N KANSAS B N OKLAHOMA B N N TEXAS N N S TEXAS A N W TEXAS N N MINNESOTA N A IOWA N A MISSOURI N A ARKANSAS N A LOUISIANA A B WISCONSIN N A ILLINOIS N A MISSISSIPPI A N MICHIGAN N A INDIANA N A OHIO N A KENTUCKY N A TENNESSEE N A ALABAMA A N NEW YORK N N VERMONT N N NEW HAMP N N MAINE N N MASS N N CONN N N RHODE ISL N N PENN N N NEW JERSEY N N W VIRGINIA N N MARYLAND N N DELAWARE N N VIRGINIA N N N CAROLINA A N S CAROLINA A N GEORGIA A N FL PNHDL A B FL PENIN A B AK N SLOPE N A AK ALEUTIAN A N AK WESTERN N A AK INT BSN A A AK S INT A A AK S COAST A N AK PNHDL A N 8 to 14 day Outlook Table STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN WASHINGTON B A OREGON B A NRN CALIF B A SRN CALIF B A IDAHO B A NEVADA B A W MONTANA B A E MONTANA B A WYOMING B A UTAH B A ARIZONA N A COLORADO N N NEW MEXICO N N N DAKOTA B A S DAKOTA B A NEBRASKA B N KANSAS B N OKLAHOMA N N N TEXAS N N S TEXAS A N W TEXAS N N MINNESOTA B A IOWA B A MISSOURI B A ARKANSAS N N LOUISIANA A B WISCONSIN B A ILLINOIS B A MISSISSIPPI A N MICHIGAN B A INDIANA B A OHIO B A KENTUCKY N A TENNESSEE N A ALABAMA A N NEW YORK B N VERMONT B N NEW HAMP B N MAINE B N MASS B N CONN B N RHODE ISL B N PENN B N NEW JERSEY N N W VIRGINIA B N MARYLAND N N DELAWARE N N VIRGINIA N N N CAROLINA N N S CAROLINA N N GEORGIA A B FL PNHDL A B FL PENIN N B AK N SLOPE A A AK ALEUTIAN A A AK WESTERN A A AK INT BSN A A AK S INT A N AK S COAST N B AK PNHDL B B LEGEND TEMPS WITH RESPECT TO NORMAL PCPN WITH RESPECT TO MEDIAN A - ABOVE N - NEAR NORMAL A - ABOVE N - NEAR MEDIAN N - NEAR NORMAL 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