PROGNOSTIC DISCUSSIONS FOR 6 TO 10 AND 8 TO 14 DAY OUTLOOKS CLIMATE PREDICTION CENTER NCEP NATIONAL WEATHER SERVICE WASHINGTON DC 3 PM EDT THURS JUL 25 2002 6 TO 10 DAY OUTLOOK FOR JUL 31 - AUG 4 2002 . . . . . . . . MODEL COMPARISONS: TODAY THE MAIN OPERATIONAL MODELS ARE IN REASONABLE AGREEMENT ON THE EXPECTED 500 HPA HEIGHT PATTERN OVER NORTH AMERICA FOR THE FIRST FOUR DAYS BUT BY DAY FIVE SOME NOTICEABLE PHASING DIFFERENCES ARE DEVELOPING...WITH THE ECMWF ABD 12Z UKMET BEING FASTER THAN THE CANADIAN AND 0Z AVN(FORMERLY MRF) WHILE THE 0Z UKMET IS THE SLOWEST. TODAYS 0Z AVN AND ECMWF ENSEMBLE MEMBERS ARE SHOWING A BIT LESS UNCERTAINTY BY DAY 6 THAN THEY WERE YESTERDAY...WITH MORE OF THE UNCERTAINTY BEING DUE TO PHASE DIFFERENCES THAN AMPLITUDE DIFFERENCES AMONG THE VARIOUS MEMBERS. THE HIGH RESOLUTION 0Z AVN IS AMONG THE MOST AMPLIFIED MEMBERS OF ITS ENSEMBLE BUT THE SAME IT TRUE OF THE HIGH RESOLUTION ECMWF WHICH HAS ONE OF THE STRONGEST RIDGES OVER THE EASTERN PACIFIC ON DAY 6 WITH A 5820 METER 500 HPA HEIGHT OVER CENTRAL ALASKA. THE DAILY MRF AND ECMWF ENSEMBLE MEANS FOR DAYS 6 THROUGH 10 ARE IN GOOD AGREEMENT ON THE 5820 METER HEIGHT LINE ...SHOWING A PROGRESSIVE PATTERN WITH A TROUGH OVER THE EASTERN PACIFIC ON DAY 6 MOVING TO THE WEST COAST BY DAY 10 WHILE ANOTHER TROUGH MOVES FROM THE GREAT LAKES ON DAY 6 TO THE WESTERN ATLANTIC ON DAY 10. IN BETWEEN THE TROUGHS IS A FLAT BUT MODERATE AMPLITUDE RIDGE. THE OVERALL MEAN 500 HPA SOLUTIONS FOR THE 6 TO 1O DAY PERIOD CONTINUE TO SHOW SIGNIFICANT RUN-TO-RUN CHANGES...WITH TODAYS DAVA AND ECMWF SOLUTIONS BEING FAIRLY CONSISTENT WITH THEIR PREVIOUS RUNS WHILE THE 0Z AVN AND ENSEMBLE MEAN ARE IN REASONABLE AGREEMENT WITH EACH OTHER BUT MORE AMPLIFIED THAN YESTERDAYS SOLUTIONS. ALL SOLUTIONS HAVE A STRONG POSITIVE HEIGHT ANOMALY IN THE VICINITY OF THE DAVIS STRAIT WHICH TELECONNECTS TO UNDERCUTTING NEGATIVE ANOMALIES OVER THE NORTHEASTERN U.S. THIS DISAGREES WITH THE ECMWF SOLUTION THERE. HOWEVER TELECONNECTIONS FRON THE STRONG POSITIVE ANOMALY THAT THE ECMWF FORECASTS NEAR 65N/155W TELECONNECT FAIRLY WELL WITH ITS DOWNSTREAM PATTERN INCLUDING POSITIVE ANOMALIES OVER THE EASTERN U.S. ...BUT THE PATTERN LACKS STATISTICAL SIGNIFICANCE. A NUMBER OF MODELS AND ENSEMBLE MEMBERS ARE STILL SHOWING AN 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. TODAY THERE ARE A FEW LESS EXAMPLES OF SUCH A SOLUTION BUT SEVERAL OPERATIONAL MODELS HAVE BEEN FAIRLY CONSISTENT IN SHOWING THIS FOR SEVERAL DAYS. STILL SUCH A SCENARIO HAS TO BE CONSIDERED UNCERTAIN AT THIS TIME RANGE THOUGH. CONFIDENCE IN TODAYS FORECAST IS RATED AS BELOW AVERAGE...2 ON A 1-5 SCALE... DUE TO RUN-TO-RUN MODEL INCONSISTENCY. THE OFFICIAL 500-HPA HEIGHT FORECAST FOR THE 6 TO 10 DAY PERIOD USES 25 PERCENT OF TODAYS ECMWF SOLUTION CENTERED ON DAY 7...25 PERCENT OF TODAYS AVN ENSEMBLE MEAN CENTERED ON DAY 8...25 PERCENT OF TODAYS HIGH RESOLUTION OZ AVN CENTERED ON DAY 8...AND 25 PERCENT OF TODAYS DAVA MODEL CENTERED ON DAY 8. MODEL OF THE DAY: NONE THE TEMPERATURE PROG IS A CONSENSUS OF THE KLEIN AND NEURAL NETWORK SPECIFICATIONS FROM THE OFFICIAL HEIGHT PROG. THE PRECIPITATION PROG IS A CONSENSUS OF THE NEURAL NETWORK SPECIFICATION FROM THE OFFICIAL HEIGHT PROG...ANALOGS FROM THE ENSEMBLE MEAN...AVN...AND ECMEF...THE AVN MODEL ACCUMULATED PRECIPITATION...AND THE CALIBRATED AVN PRECIPITATION. . . . . . . . . 8 TO 14 DAY OUTLOOK FOR AUG 2 - AUG 8 2002 THERE IS GOOD AGREEMENT BETWEEN THE 0Z AVN...ENSEMBLE MEAN...AND DAVA MODEL SOLUTIONS TODAY AND ALL AGREE WELL WITH YESTERDAYS SOLUTIONS. THESE SOLUTIONS CONTINUE A PATTERN MUCH LIKE THAT FOR DAYS 6 THROUGH 10. CONFIDENCE IS BELOW AVERAGE TODAY...RATED 3 ON A SCALE OF 1-5. THE BLENDED 500-MB HEIGHT PATTERN USES 30 PERCENT OF TODAYS ENSEMBLE MEAN CENTERED ON DAY 11...10 PERCENT OF TODAYS HIGH RESOLUTION 0Z AVN CENTERED ON DAY 11...30 PERCENT OF TODAYS ENSEMBLE MEAN CENTERED ON DAY 7...15 PERCENT OF TODAYS DAVA MODEL CENTERED ON DAY 11...AND 15 PERCENT OF TODAYS ECMWF SOLUTION CENTERED ON DAY 7. 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. THE PRECIPITATION PROG IS A CONSENSUS OF THE NEURAL NETWORK SPECIFICATIONS FROM THE OFFICIAL HEIGHT PROG...ANALOGS FROM THE ENSEMBLE MEAN...THE AVN MODEL ACCUMULATED PRECIPITATION...AND THE CALIBRATED AVN 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 A OREGON B N NRN CALIF B N SRN CALIF B N IDAHO N A NEVADA N N W MONTANA N A E MONTANA N A WYOMING A N 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 A IOWA A N MISSOURI A N ARKANSAS A N LOUISIANA A N WISCONSIN A N ILLINOIS A N MISSISSIPPI A N MICHIGAN A N INDIANA A N OHIO A N KENTUCKY A N TENNESSEE A N ALABAMA A N NEW YORK A 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 A N W VIRGINIA A N MARYLAND A N DELAWARE A N VIRGINIA A N N CAROLINA A N S CAROLINA N N GEORGIA N N FL PNHDL N N FL PENIN N A AK N SLOPE A N 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 8 to 14 day Outlook Table STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN WASHINGTON B A OREGON B N NRN CALIF B N SRN CALIF B N IDAHO N N NEVADA N N W MONTANA B A E MONTANA N A WYOMING N N UTAH N N ARIZONA N N COLORADO A N NEW MEXICO A N N DAKOTA N A S DAKOTA A A NEBRASKA A N KANSAS A N OKLAHOMA A B N TEXAS A N 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 B NEW HAMP N N MAINE N B MASS N N CONN N N RHODE ISL N N PENN A B NEW JERSEY N B 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 A N AK ALEUTIAN N N AK WESTERN A N AK INT BSN N N AK S INT N N AK S COAST N N AK PNHDL B A 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