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 FEB 27 2002 6 TO 10 DAY OUTLOOK FOR MAR 5 - 9 2002 . . . . . . . . MODEL COMPARISONS: TODAYS MODELS CONTINUE TO INDICATE A PREDOMINANTLY COLD PATTERN FOR MUCH OF THE NORTHERN AND EASTERN PART OF THE U.S. THE DAILY MRF HAS NOW LOWERED HEIGHTS OFF THE PACIFIC NORTHWEST COAST MORE IN KEEPING WITH TELECONNECTIONS FROM THE POSITIVE ANOMALY PREDICTED TO BE CENTERED NEAR THE SOUTHWESTERN COAST OF ALASKA... WHILE THE ECMWF HAS GONE POSSIBLY A STEP FURTHER THAN THE OTHER MODELS WITH THE PACIFIC TROUGH DIGGING SOUTHWESTWARD WELL OFF THE COAST AND POPPING A WEAK RIDGE OVER THE WESTERN U.S. ... WITH A SEPARATE FAIRLY STRONG TROUGH OVER EASTERN NORTH AMERICA. IN GENERAL... THE MODELS HAD WEAKLY NEGATIVE HEIGHT ANOMALIES OVER THE SOUTHERN AND SOUTHEASTERN U.S. ... WHICH MAY HAVE RESULTED IN TOO COLD TEMPERATURE SPECIFICATIONS BY BOTH THE KLEIN AND NEURAL NET... IN VIEW OF THE INDIVIDUAL DAILY MAPS THAT SHOW THESE AREAS HAVING A FEW MILD DAYS DURING THE FORECAST PERIOD. AVERAGE MODEL AC SCORES FOR THE 500 HPA LEVEL PROGS DURING THE PAST TWO MONTHS SHOW THE BEST AVERAGE PERFORMANCE BY THE ENSEMBLE MEAN FOLLOWED BY THE ECMWF MODEL. THE DAVA MODEL... WHICH HAS ONLY RECENTLY BEEN SCORED... SHOWS AN EVEN BETTER PERFORMANCE DURING THE PAST TWO WEEKS THAT IS HAS BEEN SCORED WHEN COMPARED WITH THE OTHER MODELS DURING THE SAME PERIOD. THE FORECAST POSITION OF THE STRONG RIDGE BUILDING NORTHWARD THROUGH THE BERING SEA FROM THE ALEUTIANS CONTINUES TO IMPLY COLDER AND DRIER THAN NORMAL CONDITIONS IN THE INTERIOR... SOUTHERN COASTS AND PANHANDLE OF ALASKA. . . . . . . . . CONFIDENCE IN TODAYS FORECAST IS ONLY NEAR AVERAGE... RATED 3 ON A 1-5 SCALE... DUE TO GROWING DIFFERENCES AMONG THE MODELS AND RAPID DAY-TO-DAY CHANGES WITHIN THE FORECAST PERIOD. THE OFFICIAL 500 HPA HEIGHT FORECAST FOR THE 6 TO 10 DAY PERIOD IS A BLEND OF 40 PERCENT OF TODAYS ENSEMBLE MEAN SOLUTION CENTERED ON DAY 8... 30 PERCENT OF TODAYS DAVA SOLUTION CENTERED ON DAY 8... 10 PERCENT OF TODAYS HIGH RESOLUTION MRF CENTERED ON DAY 8... AND 20 PERCENT OF TODAYS ECMWF RUN CENTERED ON DAY 7. . . . . . . . . MODEL OF THE DAY: ENSEMBLE MEAN FOLLWED CLOSELY BY THE ECMWF. THE TEMPERATURE PROG IS BASED PRIMARILY ON THE MRF ENSEMBLE MEAN 850 HPA BIAS- CORRECTED TEMPERATURE OUTPUT... AND ON THE KLEIN AND NEURAL NET SPECIFICATIONS FROM THE OFFICIAL BLEND. THE MOS TEMPERATURES WERE ALSO CONSIDERED TO BETTER ACCOUNT FOR THE DAILY VARIABILITY WITHIN THE FORECAST PERIOD. 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 AND DAILY PROGS. THE NEURUAL NET PRECIPITATION SPECIFICATION WAS ALSO CONSIDERED. 8 TO 14 DAY OUTLOOK FOR MAR 7 - 13 2002 MODEL COMPARISONS: DURING THE WEEK 2 TIMEFRAME... THE STRONGEST NEAGITVE HEIGHT ANOMALIES ARE PREDICTED TO SHIFT DECISIVELY TOWARDS BRITISH COLUMBIA BY ALL THE MODELS AS WOULD BE EXPECTED FROM TELECONNECTION CONSIDERATIONS WITH THE STRONG RIDGE OVER THE EASTERN ALEUTIANS. THE MRF MEAN HAD A VERY STRONG PATTERN... ESPECIALLY THE AMPLITUDE OF THE DOWNSTREAM RIDGE PREDICTED TO BUILD OVER THE NORTHEASTERN U.S. ... IN GOOD AGREEMENT WITH THE SOMEWHAT WEAKER BUT NEVERTHELESS FAIRLY STRONG ENSEMBLE MEAN. THE DAVA MODEL HAD ABOUT THE SAME PHASE... BUT NOT AS FAR WEST ON THE BRITISH COLUMBIA NEGATIVE ANOMALY CENTER AND SOMEWHAT WEAKER OVERALL ON THE STRENGTH OF MOST OF ITS ANOMALIES. . . . . . . . . CONFIDENCE IN TODAYS FORECAST IS ACTUALLY SLIGHTLY ABOVE AVERAGE... RATED 4 ON A SCALE OF 1-5... DUE TO BETTER AGREEMENT AMONG THE WEEK TWO TOOLS THAN THERE WAS AMONG THE 6-10 DAY TOOLS... AND THE FACT THAT THE CONSENSUS PATTERN WAS IN EXCELLENT AGREEMENT WITH THE MODAL TELECONNECTION FROM THE ALEUTIAN POSITIVE ANOMALY CENTER. IT APPEARS AS THOUGH THE MODELS HAVE DIFFERENT TIME SCALES IN WHICH THEY ADJUST THE PATTERN OVER NORTH AMERICA TO THE ALEUTIAN RIDGE... BUT THEY ALL HAVE A FAIRLY STABLE PATTERN IN PLACE BY THE 8-14 DAY PERIOD. THE OFFICIAL 500 HPA HEIGHT FORECAST FOR THE 8 TO 14 DAY PERIOD CONSISTS OF 50 PERCENT OF TODAYS ENSEMBLE MEAN CENTERED ON DAY 11... 10 PERCENT OF TODAYS MRF CENTERED ON DAY 11... 20 PERCENT OPF TODAYS DAVA CENTERED ON DAY 11... 10 PERCENT OF TODAYS ENSEMBLE MEAN CENTERED ON DAY 7... AND 10 PERCENT OF TODAYS ECMWF 5-DAY MEAN CENTERED ON DAY 7. THE TEMPERATURE OUTLOOK IS BASED ON A CONSENSUS OF THE MRF ENSEMBLE 850 HPA TEMPERATURE ANOMALIES CORRECTED FOR RECENT MODEL BIASES... AND THE KLEIN AND NEURAL NET SPECIFICATIONS FROM THE BLENDED PROG. THE PRECIPITATION FORECAST IS BASED PRIMARILY ON THE MRF ACCUMULATED PRECIPI- TATION CORRECTED FOR RECENT ERRORS/BIASES...AND SUBJECTIVELY MODIFIED TO BE CONSISTENT WITH ANTICIPATED STORM TRACKS DURING THIS 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 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. 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. 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 B N OREGON B N NRN CALIF N A SRN CALIF A N IDAHO N N NEVADA A A W MONTANA B A E MONTANA B A WYOMING N N UTAH N N ARIZONA A B COLORADO A B NEW MEXICO A B N DAKOTA B A S DAKOTA B N NEBRASKA N B KANSAS N B OKLAHOMA A B N TEXAS A B S TEXAS A B W TEXAS A B MINNESOTA B A IOWA B N MISSOURI N N ARKANSAS A N LOUISIANA A N WISCONSIN B A ILLINOIS B A MISSISSIPPI N N MICHIGAN B A INDIANA B N OHIO B N KENTUCKY B N TENNESSEE B N ALABAMA N 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 B N W VIRGINIA B N MARYLAND B B DELAWARE B B VIRGINIA B B N CAROLINA B B S CAROLINA B B GEORGIA B B FL PNHDL B B FL PENIN N B AK N SLOPE A N AK ALEUTIAN A N AK WESTERN A B AK INT BSN B B AK S INT B B AK S COAST B B AK PNHDL B B 8 to 14 day Outlook Table STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN WASHINGTON B N OREGON B A NRN CALIF N A SRN CALIF N A IDAHO N N NEVADA N A W MONTANA B N E MONTANA B N WYOMING N N UTAH A A ARIZONA A A COLORADO A N NEW MEXICO A B N DAKOTA B N S DAKOTA B N NEBRASKA N B KANSAS N B OKLAHOMA N N N TEXAS A N S TEXAS A N W TEXAS A B MINNESOTA B A IOWA B A MISSOURI N A ARKANSAS A A LOUISIANA A N WISCONSIN B A ILLINOIS N A MISSISSIPPI A A MICHIGAN B A INDIANA N A OHIO N N KENTUCKY A N TENNESSEE A N ALABAMA A B NEW YORK N N VERMONT N N NEW HAMP N B MAINE N N MASS N B CONN N B RHODE ISL N B PENN N B NEW JERSEY N B W VIRGINIA N B MARYLAND N B DELAWARE N B VIRGINIA A B N CAROLINA A B S CAROLINA A B GEORGIA A B FL PNHDL A B FL PENIN N B AK N SLOPE A N AK ALEUTIAN A N AK WESTERN A B AK INT BSN B B AK S INT N B AK S COAST B 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