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 JUL 17 2002 6 TO 10 DAY OUTLOOK FOR JUL 23 - 27 2002 . . . . . . . . MODEL COMPARISONS: THERE IS GOOD AGREEMENT AMONG MODEL FORECASTS OF THE MAIN FEATURES OF THE NORTH AMERICAN CIRCULATION FOR THE 6-10 DAY PERIOD. A TROUGH IS EXPECTED TO DEVELOP OVER THE CENTRAL PORTION OF THE U.S. - WITH THE WESTERN RIDGE PREDICTED TO RETROGRADE OFF THE WEST COAST. 500-HPA HEIGHTS ANMOALIES ARE WEAKLY POSITIVE OVER THE EAST. THERE IS GENERAL CONSENSUS FOR THE FORMATION OF A DEEP ALEUTIAN LOW THAT SHOULD BRING STORMS INTO SOUTHERN ALASKA. WITH ONLY MINOR DIFFERENCES BETWEEN THE MODELS IN THE PREDICTED STRENGTH AND POSITION OF THE TROUGH IN THE CENTRAL U.S. - THE MAIN PROBLEMS ANTICIPATED WITH THIS FORECAST CONCERN TIMING OF THE FRONTAL BOUNDARY EXPECTED TO MOVE SOUTHWARD IN THE PLAINS AND MISSISSIPPI VALLEY - AND THE EASTWARD EXTENT OF THE COOL AIR ASSOCIATED WITH THE TROUGH. . . . . . . . . CONFIDENCE IN TODAYS FORECAST IS RATED AS ABOVE AVERAGE... 4 ON A 1-5 SCALE. THE OFFICIAL 500-HPA HEIGHT FORECAST FOR THE 6 TO 10 DAY PERIOD USES 35 PERCENT OF TODAYS ECMWF SOLUTION CENTERED ON DAY 7... 30 PERCENT OF TODAYS MRF ENSEMBLE MEAN CENTERED ON DAY 8...25 PERCENT OF TODAYS HIGH RESOLUTION MRF CENTERED ON DAY 8... AND 10 PERCENT OF TODAYS DAVA MODEL CENTERED ON DAY 8. MODEL OF THE DAY: ECMWF THE TEMPERATURE PROG IS BASED MOSTLY ON KLEIN SPECIFICATION EQUATIONS. THE MOS FORECASTS OF 6-10 DAY MEAN TEMPERATURES APPEAR TOO WARM THROUGHOUT MUCH OF THE PLAINS AND SOUTHEAST AND HAVE BEEN SUBSTANTIALLY REVISED TOWARD THE OTHER TOOLS. THE PRECIPITATION PROG IS BASED MAINLY ON THE BIAS CORRECTED MRF ACCUMULATED PRECIPITATION... CALIBRATED PRECIPITATION FROM TODAYS MRF... AND ANALOGS FROM THE PRINCIPAL MODELS. THE RETROGRESSION OF THE WESTERN RIDGE INTO THE NORTH PACIFIC SHOULD INCREASE NORTHERLY FLOW OVER THE ROCKY MOUNTAINS AND GREAT BASIN AND SUPRESS SOUTHWEST MONSOON RELATED PRECIPITATION. . . . . . . . . 8 TO 14 DAY OUTLOOK FOR JUL 25 - 31 2002 THERE IS GOOD AGREEMENT BETWEEN THE MRF HIGH RESOLUTION... MRF ENSEMBLE MEAN AND DAVA MODEL SOLUTIONS TODAY. THE FORECAST CIRCULATION PATTERN IS QUITE SIMILAR TO THE ONE PREDICTED FOR THE 6-10 DAY PERIOD. CONFIDENCE IS ABOVE AVERAGE TODAY...RATED 4 ON A SCALE OF 1-5. THE BLENDED 500-MB HEIGHT PATTERN USES 50 PERCENT OF TODAYS HIGH RESOLUTION MRF CENTERED ON DAY 11... 40 PERCENT OF TODAYS MRF ENSEMBLE MEAN CENTERED ON DAY 11 AND 10 PERCENT OF TODAYS DAVA MODEL CENTERED ON DAY 11. THE TEMPERATURE OUTLOOK IS BASED ON THE KLEIN SPECIFICATIONS FROM THE 500-MB BLENDED PROG AND ANALOGS FROM THE HIGH RESOLUTION MRF. THE PRECIPITATION FORECAST IS BASED ON THE CALIBRATED PRECIPITATION FROM TODAYS MRF... ANALOGS FROM THE DIFFERENT MODELS... BIAS CORRECTED MRF ACC- UMULATED PRECIPITATION AND NEURAL NET SPECIFICATIONS FROM THE OFFICIAL HEIGHT PROG. FORECASTER: D. UNGER . . . . . . . . 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 JULY 18 2002. 6 to 10 day Outlook Table STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN WASHINGTON A B OREGON A B NRN CALIF A B SRN CALIF A N IDAHO A B NEVADA A B W MONTANA N B E MONTANA N B WYOMING A B UTAH A B ARIZONA A N COLORADO A B NEW MEXICO A B N DAKOTA N N S DAKOTA N N NEBRASKA N N KANSAS N N OKLAHOMA B N N TEXAS B A S TEXAS B A W TEXAS A N MINNESOTA N A IOWA N A MISSOURI B A ARKANSAS B A LOUISIANA B A WISCONSIN N N ILLINOIS N N MISSISSIPPI B A MICHIGAN N B INDIANA N B OHIO N B KENTUCKY B A TENNESSEE B A ALABAMA B A NEW YORK A N VERMONT A B NEW HAMP A N MAINE A B MASS A N CONN A N RHODE IS A N PENN N N NEW JERSEY A A W VIRGINIA N N MARYLAND N A DELAWARE N A VIRGINIA N A N CAROLINA N A S CAROLINA N A GEORGIA B A FL PNHDL N N FL PENIN N N AK N SLOPE A B AK ALEUTIAN B A AK WESTERN N N AK INT BSN N N AK S INT N A AK SO COAST B A AK PNHDL N 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 N SRN CALIF A N IDAHO A B NEVADA A B W MONTANA A B E MONTANA N B WYOMING N B UTAH A B ARIZONA A B COLORADO N B NEW MEXICO A B N DAKOTA B B S DAKOTA B B NEBRASKA B N KANSAS B A OKLAHOMA B A N TEXAS B A S TEXAS B A W TEXAS N N MINNESOTA N B IOWA B N MISSOURI B A ARKANSAS B A LOUISIANA B A WISCONSIN N B ILLINOIS N N MISSISSIPPI B A MICHIGAN N N INDIANA N N OHIO N N KENTUCKY N A TENNESSEE B A ALABAMA B A NEW YORK A N VERMONT A N NEW HAMP A B MAINE A B MASS A N CONN A N RHODE IS A N PENN N N NEW JERSEY A N W VIRGINIA N N MARYLAND N N DELAWARE N N VIRGINIA N A N CAROLINA N A S CAROLINA B A GEORGIA B A FL PNHDL N A FL PENIN N B AK N SLOPE B B AK ALEUTIAN B A AK WESTERN B A AK INT BSN B N AK S INT B A AK SO COAST B A AK PNHDL N N 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