PROGNOSTIC DISCUSSIONS FOR 6 TO 10 AND 8 TO 14 DAY OUTLOOKS CLIMATE PREDICTION CENTER NCEP NATIONAL WEATHER SERVICE WASHINGTON DC 3 PM EDT WED MAY 29 2002 6 TO 10 DAY OUTLOOK FOR JUNE 4 - 8 2002 . . . . . . . . MODEL COMPARISONS: THE MRF ENSEMBLE MEAN... ECMWF.. HIGH RESOLUTION MRF... AND DAVA MODELS NOW HAVE MOST OF THE HIGH LATITUDE BLOCKING PREDICTED OVER THE ATLANTIC AND ACROSS THE ARCTIC COAST OF EURASIA. AGREEMENT OF THE MODELS OVER THE THE NORTH AMERICA SECTOR CONTINUES TO IMPROVE... AND ALL MODELS HAVE A DEEP LOW IN THE GULF OF ALASKA... BUT THE ECMWF IS AGAIN THE MOST DIFFERENT FROM THE OTHERS WITH ITS MAIN POSITIVE ANOMALY IN THE NORTH AMERICAN SECTOR OVER BRITISH COLUMBIA AND THE CANADIAN PRAIRIES. THE DAVA AND ENSEMBLE MEANS HAVE WEAK RIDGES OVER THE EAST... IN SLIGHTLY DIFFERENT LOCATIONS... AND THE MRF HAS A BAND OF MODERATELY STRONG POSITIVE ANOMALY CENTERS STRETCHING ACROSS THE NORTHERN U.S. WITH A POORLY DEFINED CENTER OVER THE NORTHEAST AND A STRONGER ONE JUST OFF THE OREGON COAST. THE DAILY PROGS OF THE MODELS... INCLUDING THE UKMET... ARE IN REASONABLY GOOD AGREEMENT THROUGH DAY 5. THE ENSEMBLE SPAGHETTI CHARTS SHOW BETTER AGREEMENT ON THE MAIN FEATURES OF THE FORECAST PATTERNS TODAY... WITH THE MAIN UNCERTAINTY ON DAY 3 AS TO HOW FAST A TROUGH WILL DEVELOP AT LOW LATITUDES OVER THE SOUTHEAST... AND THE PHASING AND AMPLITUDE OF THE TROUGH OVER THE SOUTHWEST FOR THE MEAN PATTERNS CENTERED ON DAY 8 AND DAY 11. AGREEMENT AT HIGH LATITUDES IN THE NORTH AMERICAN SECTOR IS BETTER THAN IT WAS THE PAST TWO DAYS. CONFIDENCE IS NOW RATED AS AVERAGE TODAY... 3 ON A SCALE OF 1 TO 5... DUE TO BETTER CONTINUTIY FROM ONE DAY TO THE NEXT AND SOMEWHAT BETTER AGREEMENT AMONG THE MODELS THAN EARLIER THIS WEEK. THE OFFICIAL 500-MB HEIGHT FORECAST FOR THE 6 TO 10 DAY PERIOD IS COMPOSED OF 30 PERCENT OF THE MRF ENSEMBLE MEAN CENTERED ON DAY 8 ... 15 PERCENT OF THE ECMWF SOLUTION CENTERED ON DAY 7 ... 15 PERCENT OF THE HIGH RESOLUTION MRF CENTERED ON DAY 8... 10 PERCENT OF YESTERDAYS ECMWF CENTERED ON DAY 6... AND 30 PERCENT OF THE DAVA CENTERED ON DAY 8. MODEL OF THE DAY: DAVA AND ENSEMBLE MEAN THE TEMPERATURE PROG IS BASED MAINLY ON THE MEAN MOS TEMPERATURES FROM THE DAILY PROGS AND THE NEURAL NET AND THE KLEIN TEMPERATURE SPECIFICATIONS FROM THE BLENDED 500-MB HEIGHTS... WHICH WERE IN FAIRLY GOOD AGREEMENT IN MOST AREAS. RECENT BIASES IN MODEL 850MB TEMPERATURE FORECASTS WERE ALSO CONSIDERED. THE PRECIPITATION PROG IS BASED ON MRF MODEL PRECIPITATION CORRECTED FOR RECENT BIASES... NEURAL NET SPECIFICATIONS FROM THE OFFICIAL HEIGHT PROG... AND THE CALIBRATED BIAS CORRECTED MRF OPUTPUT. THE MRF ENSEMBLES INDICATE THAT THERE WILL BE ACTIVE SHORT WAVE DISTURBANCES CROSSING THE MIDDLE OF THE COUNTRY FROM THE CENTRAL GREAT PLAINS TO THE NORTHEAST... SOMEWHAT SIMILAR TO RECENT OBSEREVED PATTERNS... BUT AGREEMENT ON DETAILS IS INSUFFICIENT TO FIRM UP A MORE CONFIDENT PROG. ANALOGS TO THE MODELS WERE ALSO CONSIDERED. . . . . . . . . 8 TO 14 DAY OUTLOOK FOR JUNE 6 - 12 2002 MODEL COMPARISONS: THE MODEL PROGS FOR THE WEEK TWO PERIOD ARE IN FAIR AGREEMENT OVERALL... WITH THE MRF BEING QUITE SIMILAR TO THE ENSEMBLE MEAN BUT SOMEWHAT MORE PROGRESSIVE AND AS USUAL MORE AMPLIFIED. THE DAVA HAS THE ADVANTAGE OF LITTLE OR NO LOW LATITUDE NEGATIVE HEIGHT BIAS. THE BLENDED WEEK TWO PATTERN SHOWS A REASONABLE MODERATE PROGRESSION OF LARGE- SCALE FEATURES IN THE VICINITY OF NORTH AMERICA FROM THEIR 6-10 DAY POSITIIONS. HEIGHTS UNDERGO A GRADUAL FALL OVER ALAKSA WITH TIME AS WELL. CONFIDENCE IS NEAR AVERAGE FOR A WEEK TWO FORECAST AT THIS TIME OF YEAR... RATED 3 ON A SCALE FROM 1 TO 5. THE OFFICIAL 500-MB HEIGHT FORECAST FOR THE 8 TO 14 DAY PERIOD IS COMPOSED OF 40 PERCENT OF THE TODAYS MRF ENSEMBLE MEAN CENTERED ON DAY 11... 25 PERCENT OF THE HIGH RESOLUTION MRF CENTERED ON DAY 11... 25 PERCENT OF TODAYS DAVA CENTERED ON DAY 11... AND 10 PERCENT OF TODAYS ECMWF CENTERED ON DAY 7. THE TEMPERATURE OUTLOOK IS BASED ON THE KLEIN AND NEURAL NET SPECIFICATIONS FROM THE OFFICIAL HEIGHT PROG... WITH CONSIDERATION OF THE BIAS CORRECTED MODEL MEAN 850MB TEMPERATURE ANOMALIES. THE PRECIPITATION FORECAST IS BASED ON SPECIFICATIONS FROM THE NEURAL NET FROM THE OFFICIAL HEIGHT PROG AND MRF OUTPUT CORRECTED FOR RECENT BIASES. THE LATTER HAS DISPLAYED AN EVEN GREATER WET BIAS FOR THE 8-14 DAY PERIOD THAN IT HAS FOR THE 6-10 DAY PERIOD. ANANLOGS TO THE MODELS WERE ALSO CONSIDERED. 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...THURSDAY JUNE 13. 6 to 10 day Outlook Table STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN WASHINGTON A B OREGON A B NRN CALIF A N SRN CALIF N N IDAHO N N NEVADA A N W MONTANA N N E MONTANA N N WYOMING N A UTAH N N ARIZONA A N COLORADO N A NEW MEXICO A N N DAKOTA B B S DAKOTA B N NEBRASKA B A KANSAS B A OKLAHOMA N A N TEXAS A N S TEXAS A B W TEXAS A A MINNESOTA B B IOWA B N MISSOURI N N ARKANSAS A N LOUISIANA A B WISCONSIN N B ILLINOIS N N MISSISSIPPI A B MICHIGAN N N INDIANA A N OHIO A A KENTUCKY A A TENNESSEE A A ALABAMA A N NEW YORK N N VERMONT B B NEW HAMP B B MAINE B B MASS B N CONN N N RHODE ISL N N PENN N A NEW JERSEY N N W VIRGINIA A A MARYLAND N A DELAWARE N A VIRGINIA A A N CAROLINA A A S CAROLINA A N GEORGIA A N FL PNHDL A B FL PENIN A N AK N SLOPE A B AK ALEUTIAN N N AK WESTERN A B AK INT BSN A B AK S INT A N AK S COAST A A AK PNHDL A N 8 to 14 day Outlook Table STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN WASHINGTON A B OREGON A B NRN CALIF A B SRN CALIF N N IDAHO A B NEVADA A N W MONTANA N N E MONTANA N N WYOMING N N UTAH A N ARIZONA N N COLORADO N N NEW MEXICO N N N DAKOTA N B S DAKOTA N B NEBRASKA N N KANSAS N A OKLAHOMA N A N TEXAS N N S TEXAS N B W TEXAS N N MINNESOTA B B IOWA B B MISSOURI B N ARKANSAS N N LOUISIANA N B WISCONSIN B B ILLINOIS B N MISSISSIPPI N N MICHIGAN B N INDIANA B N OHIO N A KENTUCKY N A TENNESSEE N A ALABAMA N N NEW YORK N A VERMONT N N NEW HAMP N N MAINE N N MASS N N CONN N N RHODE ISL N N PENN N A NEW JERSEY N A W VIRGINIA N A MARYLAND N A DELAWARE N A VIRGINIA N A N CAROLINA A A S CAROLINA A N GEORGIA A N FL PNHDL A N FL PENIN A N AK N SLOPE A N AK ALEUTIAN N N AK WESTERN A B AK INT BSN A B AK S INT N N AK S COAST N N AK PNHDL N A 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