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 24 2002 6 TO 10 DAY OUTLOOK FOR JUL 30 - AUG 3 2002 . . . . . . . . MODEL COMPARISONS: TODAY THE MAIN OPERATIONAL MODELS ARE IN REASONABLE AGREEMENT ON THE EXPECTED 500 HPA HEIGHT LONG WAVE PATTERN FOR THE FIRST FIVE DAYS...WITH TYPICAL DIFFERENCES IN THE SHORT WAVES DEVELOPING BY DAY 4. TODAY MRF AND ECMWF ENSEMBLE MEMBERS ARE SHOWING SIGNIFICANT UNCERTAINTY BY DAY 6. THE HIGH SPREAD CONTINUES FOR BOTH MRF AND ECMWF ENSEMBLES THROUGHOUT THE 6 TO 10 DAY PERIOD... ALTHOUGH THE MRF AND ECMWF ENSEMBLE MEANS ARE IN REASONABLE AGREEMENT ON THE 5820 METER HEIGHT LINE WHICH SHOWS WEAK TROUGHS ALONG THE U.S. EAST AND WEST COASTS AND A FLAT RIDGE OVER THE CENTER OF THE NATION. THE MEAN 500 HPA SOLUTIONS FOR THE 6 TO 1O DAY PERIOD FROM THE HIGH RESOLUTION MRF AND ECMWF RUNS CONTINUE TO SHOW SIGNIFICANT RUN-TO-RUN CHANGES...ESPECIALLY THE ECMWF... WHILE THE MRF ENSEMBLE MEAN AND DAVA ARE IN GOOD AGREEMENT WITH EACH OTHER AND WITH THEIR PREVIOUS TWO RUNS. TODAYS ECMWF IS CONSIDERABLY DIFFERENT FROM ITS SOLUTION OF YESTERDAY AND HAS GONE TOWARD A SOLUTION MORE LIKE THAT FROM THE MRF ENSEMBLE MEAN AND DAVA. BOTH THE HIGH RESOLUTION MRF AND ECMWF HAVE A FAIRLY DEEP AND SHARP...POSITIVELY TILTED MEAN TROUGH FROM WEST-CENTRAL CANADA TO OFF THE NORTHWEST U.S. COAST WHILE THE MRF ENSEMBLE MEAN AND DAVA HAVE WEAK NEUTRALLY TILTED MEAN TROUGHS ALONG THE U.S.-CANADA WEST COAST. TODAYS ECMWF SOLUTION HAS A MEAN TROUGH THROUGH THE CANADIAN MARITIMES TO THE WESTERN ATLANTIC WHILE THE MRF HAS A MEAN TROUGH ABOUT 15 DEGREES FARTHER WEST. THE MRF ENSEMBLE MEAN AND DAVA ARE MUCH LESS AMPLIFIED HAVING A RATHER FLAT FLOW OVER NORTH AMERICA WITH WEAK RIDGE OVER THE MIDDLE OF THE NATION AND WEAK FLANKING TROUGHS NEAR THE WEST AND EAST COASTS. HOWEVER ALL SOLUTIONS HAVE A STRONG BLOCKING RIDGE OVER THE DAVIS STRAIT. TELECONNECTIONS FROM THE POSITIVE HEIGHT ANOMALY CENTER THAT THE MRF ENSEMBLE MEAN AND DAVA FORECAST SOUTH OF ALASKA SUPPORT THEIR SOLUTIONS WHILE TELECONNECTIONS FROM THE POSITIVE HEIGHT ANOMALY CENTER THAT THE MRF FORECASTS NEAR 55N/165W AND THE ECMWF FORECASTS NEAR 60N/160W DO NOT SUPPORT THE SHARP DOWNSTREAM TROUGH THOSE MODELS FORECAST FROM WEST-CENTRAL CANADA TO OFF THE COAST OF THE PACIFIC NORTHWEST. THE GULF OF ALASKA IS AN AREA WHERE THE MODELS OFTEN HAVE TROUBLE SO IT IS MORE DIFFICULT THAN USUAL TO SAY A PRIORI THAT A GIVEN SOLUTION IS LIKELY TO BE RIGHT OR WRONG IN THAT AREA. TELECONNECTIONS FROM THE NEGATIVE HEIGHT ANOMALY CENTER THAT THE MODELS FORECAST OVER BRITISH COLUMBIA DO SUPPORT THEIR DOWNSTREAM SOLUTIONS OVER THE LOWER 48 STATES. HOWEVER TELECONNECTIONS FROM THE POSITIVE HEIGHT ANOMALY CENTER THAT ALL THE SOLUTIONS HAVE OVER THE DAVIS STRAIT SUGGEST THAT MORE UNDERCUTTING NEGATIVE ANOMALIES SHOULD BE OVER THE NORTHEASTERN U.S. THAN ALL SOLUTIONS EXCEPT THE MRF HAVE. A NUMBER OF MODELS AND ENSEMBLE MEMBERS ARE SHOWING A EASTERN PACIFIC TROPICAL SYSTEM COMING FAR ENOUGH NORTH TO EITHER HAVE REMNANTS COME ASHORE IN CALIFORNIA OR AT LEAST BRING SOME TROPICAL MOISTURE OVER THE COAST. SUCH A SCENARIO REMAINS UNCERTAIN AT THIS TIME RANGE THOUGH. CONFIDENCE IN TODAYS FORECAST IS RATED AS BELOW AVERAGE...2 ON A 1-5 SCALE... DUE TO FAIRLY HIGH ENSEMBLE SPREAD. THE OFFICIAL 500-HPA HEIGHT FORECAST FOR THE 6 TO 10 DAY PERIOD USES 10 PERCENT OF TODAYS ECMWF SOLUTION CENTERED ON DAY 7...40 PERCENT OF TODAYS MRF ENSEMBLE MEAN CENTERED ON DAY 8...30 PERCENT OF TODAYS HIGH RESOLUTION MRF CENTERED ON DAY 8...AND 20 PERCENT OF TODAYS DAVA MODEL CENTERED ON DAY 8. MODEL OF THE DAY: MRF ENSEMBLE MEAN THE TEMPERATURE PROG IS A CONSENSUS OF THE KLEIN AND NEURAL NETWORK SPECIFICATIONS FROM THE OFFICIAL HEIGHT PROG...WITH CONSIDERATION OF THE ANALOGS FROM THE ENSEMBLE MEAN AND MRF. THE PRECIPITATION PROG IS A CONSENSUS OF THE NEURAL NETWORK SPECIFICATION FROM THE OFFICIAL HEIGHT PROG...ANALOGS FROM THE ENSEMBLE MEAN AND MRF...THE MRF MODEL ACCUMULATED PRECIPITATION...AND THE CALIBRATED MRF PRECIPITATION. . . . . . . . . 8 TO 14 DAY OUTLOOK FOR AUG 1 - AUG 7 2002 THERE IS GOOD AGREEMENT BETWEEN THE MRF...MRF ENSEMBLE MEAN...AND DAVA MODEL SOLUTIONS TODAY. THESE SOLUTIONS CONTINUE A PATTERN MUCH LIKE THAT FOR DAYS 6 THROUGH 10. THE HIGH RESOLUTION MRF HAS BETTER TELECONNECTIVITY BETWEEN THE POSITIVE HEIGHT ANOMALY CENTER THAT ALL THE SOLUTIONS HAVE OVER THE DAVIS STRAIT AND THE CLIMATOLOGICALLY PREFERRED ANOMALY PATTERN OVER THE NORTHEASTERN U.S. CONFIDENCE IS BELOW AVERAGE TODAY...RATED 2 ON A SCALE OF 1-5. THE BLENDED 500-MB HEIGHT PATTERN USES 25 PERCENT OF TODAYS MRF ENSEMBLE MEAN CENTERED ON DAY 11...25 PERCENT OF TODAYS HIGH RESOLUTION MRF CENTERED ON DAY 11...25 PERCENT OF TODAYS HIGH RESOLUTION MRF CENTERED ON DAY 7...AND 25 PERCENT OF TODAYS DAVA MODEL CENTERED ON DAY 11. THE TEMPERATURE PROG IS A CONSENSUS OF THE KLEIN AND NEURAL NETWORK SPECIFICATIONS FROM THE OFFICIAL HEIGHT PROG...WHICH ARE GENERALLY SUPPORTED BY THE ANALOGS FROM THE ENSEMBLE MEAN AND MRF. THE PRECIPITATION PROG IS A CONSENSUS OF THE NEURAL NETWORK SPECIFICATIONS FROM THE OFFICIAL HEIGHT PROG...ANALOGS FROM THE ENSEMBLE MEAN AND MRF...THE MRF MODEL ACCUMULATED PRECIPITATION...AND THE CALIBRATED MRF PRECIPITATION. FORECASTER: R. MARTIN . . . . . . . . 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:------------------------------------------------------ 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. ANALOG (NATURAL ANALOG) - A WEATHER MAP THAT RESEMBLES ANOTHER WEATHER MAP - USUALLY FROM DIFFERENT YEARS BUT THE SAME SEASON IN THE HISTORICAL RECORD. THE CRITERION FOR SELECTING AN ANALOG IS OFTEN THE PATTERN CORRELATION BETWEEN THE MAPS. TWO MAPS WILL JUST BEGIN TO RESEMBLE EACH OTHER TO THE HUMAN EYE AT A PATTERN CORRELATION OF ABOUT 40%. TO BE USEFUL - ANALOGS NEED TO HAVE MUCH HIGHER CORRELATIONS TO THE ORIGINAL MAP THAN THAT - 80% OR MORE. ANALOGS ARE INCREASINGLY DIFFICULT TO FIND AS THE GEOGRAPHIC REGION BEING STUDIED INCREASES IN SIZE. PERFECT ANALOGS TO THE ENTIRE NORTHERN HEMISPHERE SIMPLY DO NO EXIST - FOR PRACTICAL PURPOSES. THIS IS WHY SIMPLE NATURAL ANALOG FORECAST METHODS DO NOT WORK VERY WELL. 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 (AS OF 07/2002 THE NAME FOR ALL RUNS OF THE NCEP GLOBAL SPECTRAL MODEL). 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 - CONTERMINOUS 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. 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. LA NINA - THE COLD PHASE OF ENSO. 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 (AS OF 07/2002 RENAMED THE AVN) MRF ENSEMBLE - A SET OF MRF (AVN) 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 (AVN) ENSEMBLE. THE AVERAGE OF THESE IS THE MRF (AVN) 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 AUGUST 15 2002. 6 to 10 day Outlook Table STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN WASHINGTON B N OREGON B N NRN CALIF B N SRN CALIF B N IDAHO N N NEVADA N N W MONTANA B A E MONTANA N N WYOMING N A UTAH N N ARIZONA N N COLORADO A N NEW MEXICO A B N DAKOTA A A S DAKOTA A A NEBRASKA A N KANSAS A N OKLAHOMA A N N TEXAS A N S TEXAS A N W TEXAS A N MINNESOTA A N IOWA A N MISSOURI A N ARKANSAS A N LOUISIANA A N WISCONSIN A N ILLINOIS A N MISSISSIPPI A A MICHIGAN A N INDIANA A N OHIO A N KENTUCKY A N TENNESSEE A N ALABAMA A A NEW YORK A B VERMONT N B NEW HAMP N N MAINE N N MASS N N CONN N B RHODE ISL N N PENN A B NEW JERSEY A B W VIRGINIA A N MARYLAND A B DELAWARE A B VIRGINIA A N N CAROLINA A N 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 N N AK INT BSN N N AK S INT N B AK S COAST N B AK PNHDL B 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 N SRN CALIF B N IDAHO N N NEVADA N N W MONTANA N A E MONTANA N A WYOMING N N UTAH N N ARIZONA N N COLORADO A N NEW MEXICO A N N DAKOTA A A S DAKOTA A A NEBRASKA A N KANSAS A N OKLAHOMA A B N TEXAS A B S TEXAS A N W TEXAS A N MINNESOTA A A IOWA A A MISSOURI A N ARKANSAS A N LOUISIANA A N WISCONSIN A A ILLINOIS A A MISSISSIPPI A N MICHIGAN A N INDIANA A N OHIO A N KENTUCKY A N TENNESSEE A N ALABAMA N N NEW YORK N B VERMONT N N NEW HAMP N N MAINE N N MASS N N CONN N N RHODE ISL N N PENN A B NEW JERSEY N N W VIRGINIA A N MARYLAND A B DELAWARE N B VIRGINIA N B N CAROLINA N N S CAROLINA N N GEORGIA N N FL PNHDL N N FL PENIN N N AK N SLOPE N A AK ALEUTIAN N N AK WESTERN N A AK INT BSN B N AK S INT B N AK S COAST B N 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 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