PROGNOSTIC DISCUSSIONS FOR 6 TO 10 AND 8 TO 14 DAY OUTLOOKS CLIMATE PREDICTION CENTER NCEP NATIONAL WEATHER SERVICE WASHINGTON DC 3 PM EST MON FEB 18 2002 6 TO 10 DAY OUTLOOK FOR FEB 24 - 28 2002 . . . . . . . . MODEL COMPARISONS: MODELS ARE IN GOOD AGREEMENT FOR ONLY THE FIRST TWO DAYS ON THEIR PREDICTIONS OF THE 500 HPA CIRCULATION...WITH MORE SIGNIFICANT DIFFER- ENCES IN A SPLIT FLOW PATTERN ALREADY BEGINNING TO SHOW UP BY DAY 3. HOWEVER BY DAY 5...THE MRF AND UKMET SOLUTIONS INITIALIZED AT 00Z ARE AT LEAST HINTING AT SOME SIMILARITIES THAT FAVOR A RIDGE ALONG THE WEST COAST OF NORTH AMERICA ...AND A POSITIVELY TILTED TROUGH FROM NORTHEASTERN TO SOUTHWESTERN CANADA... AND RELATIVELY LOW AMPLITUDE FLOW WITH EMBEDDED SHORT WAVES MIGRATING ACROSS THE CONTERMINOUS U.S. FOR DAYS 6-10...THE MRF AND ECMWF MODEL RUNS PORTRAY A PATTERN WHICH MAINTAINS THE WEST COAST RIDGE AND AN EASTERN U.S. TROUGH WITH CONSIDERABLE AMPLITUDE. THE DAVA EXTENSION FROM THE DAY 5 ENSEMBLE MEAN PROG SHOWS A SIMILARLY PHASED PATTERN...THOUGH WITH MUCH LESS AMPLITUDE OVERALL. IF THE WEST COAST RIDGE AMPLIFIES MORE THAN EXPECTED DURING THIS PERIOD...WE WOULD LIKELY SEE THE ANOMALOUS COLD OVER THE LOWER 48 TO BE A BIT FURTHER WEST. . . . . . . . . CONFIDENCE IN TODAYS FORECAST IS SLIGHTLY BELOW AVERAGE...2 ON A 1-5 SCALE. THE OFFICIAL 500 HPA HEIGHT FORECAST FOR THE 6 TO 10 DAY PERIOD IS A BLEND OF 50 PERCENT OF TODAYS DAVA SOLUTION CENTERED ON DAY 8... 25 PERCENT OF TODAYS HIGH RESOLUTION MRF CENTERED ON DAY 8... AND 25 PERCENT OF TODAYS ECMWF RUN CENTERED ON DAY 7. TODAYS ENSEMBLE MEAN D+8 PROG COULD NOT BE INCLUDED IN THE BLENDED HEIGHT PROG...BUT IT WAS AVAILABLE FOR INCLUSION INTO THE WEEK 2 FORECAST. . . . . . . . . MODEL OF THE DAY: DAVA THE TEMPERATURE PROG IS BASED PRIMARILY ON THE MRF ENSEMBLE MEAN 850 HPA BIAS- CORRECTED TEMPERATURE OUTPUT... AND TO A LESSER DEGREE ON THE USUAL KLEIN AND NEURAL NET TEMPERATURE SPECIFICATIONS FROM THE OFFICIAL BLEND. THE PRECIPITATION PROG IS BASED MOSTLY ON THE MRF ACCUMULATED PRECIPITATION CORRECTED FOR RECENT BIASES...AND IS ALSO SUBJECTIVELY MODIFIED TO BE CONSIS- TENT WITH THE OFFICIAL 500 HPA HEIGHT PROG. TOWARDS THE MIDDLE OF THE 6-10 DAY PERIOD...THE MRF SHOWS A SHORT WAVE DIGGING SOUTHEASTWARD ACROSS THE CEN- TRAL AND SOUTHERN PLATEAU...WITH GULF MOISTURE BEGINNING TO MOVE UPSLOPE OVER THE HILL COUNTRY OF CENTRAL TEXAS. 8 TO 14 DAY OUTLOOK FOR FEB 26 - MAR 4 2002 MODEL COMPARISONS: BY WEEK 2...THE WEST COAST RIDGE IS PREDICTED TO RETRO- GRADE SOMEWHAT OVER THE EASTERN PACIFIC AND GULF OF ALASKA REGION...ACCORDING TO THE MRF AND THE ENSEMBLE MEAN NUMERICAL MODELS. THIS IN TURN WOULD ALLOW ANOMALOUSLY COLD AIR TO DOMINATE MUCH OF THE EAST...WITH A TENDENCY TO MOVE WESTWARD AS WELL ONCE THE INITIAL COLD AIRMASS DEPARTS THE LOWER 48. THE WARMTH OVER ALASKA ALSO SHIFTS WESTWARD TOWARD THE BERING SEA...WHILE COLDER TEMPERATURES SPREAD ACROSS EASTERN PORTIONS OF THE 49TH STATE. . . . . . . . . CONFIDENCE IN TODAYS FORECAST IS BELOW AVERAGE...RATED 2 ON A SCALE OF 1-5... LARGELY BECAUSE OF THE UNCERTAINTIES ASSOCIATED WITH THE PRECEDING 6-10 DAY PERIOD. THE OFFICIAL 500 HPA HEIGHT FORECAST FOR THE 8 TO 14 DAY PERIOD CONSISTS OF 70 PERCENT OF TODAYS ENSEMBLE MEAN CENTERED ON DAY 11... AND 30 PERCENT OF TO- DAYS MRF CENTERED ON DAY 11. THE TEMPERATURE OUTLOOK IS BASED MAINLY ON THE MRF ENSEMBLE 850 HPA TEMPERATURE ANOMALIES CORRECTED FOR RECENT MODEL BIASES...AND IS ALSO SUBJECTIVELY MODIFIED TO BE CONSISTENT WITH AN APPARENT WESTWARD DISPLACEMENT OF THE LONG WAVE PAT- TERN OVER NORTH AMERICA. THE PRECIPITATION FORECAST IS BASED PRIMARILY ON THE MRF ACCUMULATED PRECIPI- TATION CORRECTED FOR RECENT ERRORS/BIASES. FORECASTER: A. ARTUSA . . . . . . . . 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 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 - 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 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. LA NINA - THE COLD 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. 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. 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 SURFACCE 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. 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. MJO - MADDEN-JULIAN OSCILLATION - ALSO CALLED TROPICAL INTRA-SEASONAL OSCILLA- TION - A SERIES OF WAVES WITH A PERIOD AVERAGING 50 DAYS THAT MOVES SLOWLY EAST- WARD 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 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. 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 ON THURSDAY MARCH 14. 6 to 10 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 N N NEVADA A B W MONTANA N A E MONTANA B N WYOMING N B UTAH A B ARIZONA A B COLORADO N B NEW MEXICO A B N DAKOTA B N S DAKOTA B B NEBRASKA B B KANSAS N B OKLAHOMA N B N TEXAS A A S TEXAS A A W TEXAS A A MINNESOTA B B IOWA B B MISSOURI N B ARKANSAS N B LOUISIANA N N WISCONSIN B B ILLINOIS N N MISSISSIPPI N B MICHIGAN B N INDIANA N N OHIO N N KENTUCKY N N TENNESSEE N B ALABAMA N B NEW YORK N A VERMONT N A NEW HAMP N A MAINE N A MASS N A CONN N A RHODE ISL N A PENN N A NEW JERSEY N A W VIRGINIA N N MARYLAND N N DELAWARE N N VIRGINIA N N N CAROLINA N B S CAROLINA N B GEORGIA N B FL PNHDL N B FL PENIN N B AK N SLOPE A B AK ALEUTIAN N A AK WESTERN A N AK INT BSN A B AK S INT A B AK S COAST A B AK PNHDL N B 8 to 14 day Outlook Table STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN WASHINGTON A N OREGON A N NRN CALIF A B SRN CALIF A B IDAHO N N NEVADA A B W MONTANA N N E MONTANA N N WYOMING N A UTAH N N ARIZONA A B COLORADO N N NEW MEXICO N B N DAKOTA N N S DAKOTA N A NEBRASKA N A KANSAS N N OKLAHOMA N A N TEXAS N A S TEXAS N N W TEXAS N A MINNESOTA B B IOWA B N MISSOURI B A ARKANSAS N A LOUISIANA N A WISCONSIN B B ILLINOIS B N MISSISSIPPI N A MICHIGAN B B INDIANA B N OHIO B N KENTUCKY B A TENNESSEE B A ALABAMA N N NEW YORK B B VERMONT N B NEW HAMP N B MAINE N B MASS N B CONN N B RHODE ISL N B PENN B B NEW JERSEY B B W VIRGINIA B N MARYLAND B N DELAWARE B N VIRGINIA B N N CAROLINA B N S CAROLINA B B GEORGIA N N FL PNHDL N B FL PENIN N B AK N SLOPE N B AK ALEUTIAN A N AK WESTERN A N AK INT BSN N B AK S INT N B AK S COAST N B AK PNHDL B N 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