PROGNOSTIC DISCUSSIONS FOR 6 TO 10 AND 8 TO 14 DAY OUTLOOKS CLIMATE PREDICTION CENTER NCEP NATIONAL WEATHER SERVICE WASHINGTON DC 3 PM EDT MON OCT 7 2002 6 TO 10 DAY OUTLOOK FOR OCT 13 - 17 2002 . . . . . . . . MODEL COMPARISONS: SOLUTIONS FROM THE AVN...ECMWF... AVN-BASED ENSEMBLE MEAN... AND DAVA ARE IN REASONABLE AGREEMENT TODAY ON THE LONG WAVE 500 HPA HEIGHT PATTERN FOR THE 6 TO 10 DAY PERIOD...AND ARE CONSISTENT WITH THE SOLUTIONS FROM YESTERDAY. RECENT MEAN ERRORS (BIASES) IN THE HIGH RESOLUTION AVN SOLUTIONS SUGGEST THAT THE PREDICTED MOVEMENT OF THE MEAN TROUGH INTO THE MIDDLE OF THE COUNTRY WILL BE BRIEF AND PROBABLY WAS OVERDONE BY SOME OF THE MODEL RUNS LAST WEEK. THE AVN HIGH RESOLUTION MODEL HAS THE STRONGEST NEGAGATIVE ANOMALY OVER THE SOUTHWEST TODAY AND IS THE FARTHEST WEST ON THE TROUGH POSITION. THE ECMWF HAS THE MOST AMPLIFIED RIDGE OVER THE EAST AND STRONGEST ASSOCIATED POSITIVE ANOMALY OVER THE CANADIAN MARITIMES... BUT PREDICTS A RELATVELY WEAK WESTERN TROUGH. THE ENSEMBLE MEAN HAD THE TROUGH AND NEGATIVE ANOMALY FARTHEST EAST... OVER THE UPPER MISSISSIPPI VALLEY... WHICH CONTRARY TO THE USUAL SITUATION MAY HAVE THE WORST SOLUTION TODAY... AT LEAST IN VIEW OF RECENT ERRORS. MOST MODELS ALSO SHOW AN EXTREMELY STRONG BLOCKING RIDGE JUST NORTH OF SCANDINAVIA UNDERCUT BY A CHANNEL OF NEGATIVE ANOMALIES FROM THE EASTERN ATLANTIC ACROSS CENTRAL ASIA. THE POLAR VORTEX IS SHIFTED TOWARDS THE SIBERIAN COAST. TELECONNECTIONS FROM THE POSITIVE ANOMALY NEAR 50N/140W INDICATED BY ALL THE MODELS FAVOR A STRONG PROBABILITY OF NEGATIVE HEIGHT ANOMALIES OVER BOTH THE SOUTHWEST AND THE UPPER MISSISSIPPI VALLEY... SO THE ENSEMBLE MEAN SOLUTION MAY HAVE SOME MERIT. FORECAST CONFIDENCE IS ABOVE AVERAGE TODAY...4 ON A SCALE FROM 1 TO 5. THE OFFICIAL 500-HPA HEIGHT FORECAST FOR THE 6 TO 10 DAY PERIOD USES 40 PERCENT OF THE HIGH RESOLUTION OPERATIONAL AVN CENTERED ON DAY 8... 30 PERCENT OF THE ECMWF MEAN CENTERED ON DAY 7... AND 30 PERCENT OF THE DAVA MEAN CENTERED ON DAY 8. THE ENSMELBLE MEAN WAS NOT AVAILABLE TO THE BLEND PROGRAM WHEN IT WAS RUN. MODEL OF THE DAY: HIGH RESOLUTION AVN THE TEMPERATURE PROG IS BASED MAINLY ON THE KLEIN AND NEURAL NETWORK SPECIFICATIONS FROM THE OFFICIAL 500 HPA HEIGHT FORECAST WHICH WERE IN GOOD AGREEMENT WITH EACH OTHER... THE MOS SPECIFICATION... AND THE ANALOGS FROM THE OFFICIAL 500 HPA BLEND. THE PRECIPITATION PROG IS BASED ON THE NEURAL NET SPECIFICATIONS FROM THE 500 HPA BLEND... ANALOGS FROM THE BLEND... AND THE BIAS CORRECTED ACCUMULATED PRECIPITATION FROM THE AVN. . . . . . . . . 8 TO 14 DAY OUTLOOK FOR OCT 15 - 21 2002 MODEL COMPARISONS: THE MODELS PREDICT PATTERNS THAT ARE SIMILAR TO THEIR FORECASTS FOR THE 6 TO 10 DAY MEANS WITH SOME PROGRESSION OVER THE LOWER 48... BUT SHOW THE BEGINNING OF RETROGRESSION OF THE BLOCK FROM SCANDINAVIA INTO THE NORTH ATLANTIC. THE AVN ALSO SHOWS SOME RETROGRESSION OF THE POSITIVE ANOMALY AND RIDGE OFF THE WEST COAST WITH THE POSITIVE ANOMALY CENTER MOVING NW TOWARDS THE SOUTH COAST OF ALASKA. ALL MODELS SHOW WEAKER ANOMALIES OVERLALL THAN THOSE PREDICTED FOR THE 6-10 DAY PERIOD. THE OFFICIAL 8 TO 14 DAY HEIGHT PROG IS SIMILAR TO THE OFFICIAL 6 TO 10 DAY HEIGHT PROG... DUE TO BOTH THE SIMILARITY OF THE PATTERNS AND TO THE FACT THAT ABOUT EQUAL WEIGHT WAS PUT ON MEAN HEIGHT PROGS CENTERED ON DAY 7 DUE TO SUSPECTED DETERIORATION IN THE ACCURACY OF THE MODEL FORECASTS DURING THE WEEK TWO PERIOD... AS THESE PATTERNS DID NOT TELECONNECT AS WELL AS THE 6-10 DAY PATTERNS. THE CORRESPONDING TEMPERATURE AND PRECIPITATION FORECASTS ARE ALSO SIMILAR TO THEIR 6 TO 10 DAY CONTERPARTS. CONFIDENCE IN TODAYS WEEK 2 FORECAST IS ABOUT AVERAGE...3 ON A SCALE 1 TO 5. THE OFFICIAL 500-HPA HEIGHT FORECAST FOR THE 8 TO 14 DAY PERIOD USES 10 PERCENT EACH OF THE AVN ENSEMBLE MEANS CENTERED ON DAYS 7 AND 11... 20 PERCENT OF THE ECMWF 5 DAY MEAN CENTERED ON DAY 7... AND 30 PERCENT EACH OF THE AVN MEANS CENTERED ON DAYS 7 AND 11. THE DAVA DID NOT APPEAR TO TELECONNECT WELL AND HAD TOO WEAK AN ANOMALY PATTERN TO HAVE MUCH INFLUENCE SO IT WAS NOT USED. THE TEMPERATURE PROG IS BASED MAINLY ON THE KLEIN AND NEURAL NETWORK SPECIFICATIONS FROM THE OFFICIAL FORECAST 500 HPA BLEND WHICH AGREE WELL WITH EACH OTHER AND THE ANALOGS FROM THE OFFICIAL 500 HPA BLEND. THE PRECIPITATION PROG BASED MAINLY ON THE CALIBRATED ACCUMULATED PRECIPITATION AND THE BIAS CORRECTED AVN MODEL OUTPUT... AND THE NEURAL NET SPECIFICATIONS FROM THE OFFICIAL 500 HPA BLEND WITH SOME CONSIDERATION OF THE ANALOGS FROM THE OFFICIAL 500 HPA BLEND. 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 PRECIPI- TATION. THE NARRATIVE DESCRIPTION OF THE FORECAST PATTERNS FOR TEMPERATURE AND PRECIP- ITATION 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 SURFACE 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 CUR- RENTLY 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 EASTWARD 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 SOUTH- ERN 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 TELECONNEC- TIONS 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 OCTOBER 17 2002. 6 to 10 day Outlook Table STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN WASHINGTON B B OREGON B B NRN CALIF B B SRN CALIF B N IDAHO B N NEVADA B N W MONTANA B N E MONTANA B A WYOMING B A UTAH B A ARIZONA B N COLORADO B A NEW MEXICO B N N DAKOTA B A S DAKOTA B A NEBRASKA B N KANSAS B N OKLAHOMA N A N TEXAS A A S TEXAS A N W TEXAS N N MINNESOTA N A IOWA N N MISSOURI A A ARKANSAS A A LOUISIANA A N WISCONSIN A N ILLINOIS A A MISSISSIPPI A N MICHIGAN A N INDIANA A A OHIO A N KENTUCKY A N TENNESSEE A B ALABAMA A B NEW YORK A B VERMONT A B NEW HAMP A B MAINE A N MASS A B CONN A B RHODE IS A B PENN A B NEW JERSEY A B W VIRGINIA A B MARYLAND A B DELAWARE A B VIRGINIA A B N CAROLINA A B S CAROLINA A B GEORGIA A B FL PNHDL A B FL PENIN A N AK N SLOPE A A AK ALEUTIAN A N AK WESTERN A A AK INT BSN A A AK S INT A A AK SO COAST A N AK PNHDL A N 8 to 14 day Outlook Table STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN WASHINGTON B B OREGON B B NRN CALIF B B SRN CALIF B N IDAHO B N NEVADA B N W MONTANA B N E MONTANA B A WYOMING B A UTAH B A ARIZONA B N COLORADO B A NEW MEXICO B N N DAKOTA B A S DAKOTA B A NEBRASKA B A KANSAS B A OKLAHOMA B A N TEXAS B A S TEXAS N A W TEXAS B A MINNESOTA N A IOWA N A MISSOURI N A ARKANSAS N A LOUISIANA N A WISCONSIN N A ILLINOIS N A MISSISSIPPI N A MICHIGAN N A INDIANA N A OHIO A N KENTUCKY A N TENNESSEE A B ALABAMA A N NEW YORK A N VERMONT A N NEW HAMP A N MAINE A N MASS A N CONN A N RHODE IS A N PENN A B NEW JERSEY A B W VIRGINIA A B MARYLAND A B DELAWARE A B VIRGINIA A B N CAROLINA A B S CAROLINA A B GEORGIA A B FL PNHDL A N FL PENIN A B AK N SLOPE A N AK ALEUTIAN A A AK WESTERN A A AK INT BSN A A AK S INT A N AK SO COAST A N AK PNHDL B N 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