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 MAY 6 2002 6 TO 10 DAY OUTLOOK FOR MAY 12 - 16 2002 . . . . . . . . MODEL COMPARISONS: MODELS ARE IN GOOD AGREEMENT TODAY FOR BOTH THE FIRST 5 DAYS AND FOR THE 6 TO 10 DAY MEANS. THE 6 TO 10 DAYS MEANS ARE ALSO IN GOOD AGREEMENT WITH THOSE FROM YESTERDAYS RUNS. THE OVERALL PATTERN FORECASTED OVER NORTH AMERICA BY THE MODELS CONTINUES TO BE BELOW NORMAL HEIGHTS OVER MOST OF CANADA AND THE NORTHWESTERN STATES AND ABOVE NORMAL HEIGHTS OVER THE SOUTH- EASTERN TWO THIRDS OF THE LOWER 48 STATES...FAIRLY SIMILAR TO THE MOST RECENT OBSERVED 5 DAY MEAN PATTERN. THE OFFICIAL HEIGHT PROG HAS A STRONG POSITIVE ANOMALY CENTERED AT 50N/165W WHICH TELECONNECTS WELL WITH THE DOWNSTREAM PATTERN IN THE OFFICIAL HEIGHT PROG. CONFIDENCE IN THE FORECAST TODAY IS ABOVE AVERAGE...RATED 4 ON A SCALE FROM 1 TO 5...DUE TO GOOD MODEL AGREEMENT AND CONSISTENCY...AND GOOD TELECONNECTIVITY. THE OFFICIAL 500-MB HEIGHT FORECAST FOR THE 6 TO 10 DAY PERIOD WAS COMPOSED OF 20 PERCENT OF THE ECMWF CENTERED ON DAY 7...20 PERCENT OF THE OPERATIONAL MRF CENTERED ON DAY 8...20 PERCENT OF THE ENSEMBLE MEAN CENTERED ON DAY 8...10 PERCENT OF YESTERDAYS ENSEMBLE MEAN CENTERED ON DAY 7...10 PERCENT OF THE DAVA CENTERED ON DAY 8...10 PERCENT OF YESTERDAYS MRF CENTERED ON DAY 7...AND 10 PERCENT OF YESTERDAYS ECMWF CENTERED ON DAY 6. MODEL OF THE DAY: NO PREFERENCE THE TEMPERATURE PROG IS BASED ON KLEIN AND NEURAL NET SPECIFICATIONS FROM THE OFFICIAL 500 MB HEIGHT PROG...WHICH WERE IN GOOD AGREEMENT. THE PRECIPITATION PROG IS BASED ON BIAS-ADJUSTED OPERATIONAL MRF OUTPUT...THE NEURAL NET SPECIFICATIONS FROM THE OFFICIAL 500 MB HEIGHT PROG...AND ANALOGS TO THE ENSEMBLE MEAN 500 MB HEIGHT FIELD CENTERED ON DAY 8. . . . . . . . . 8 TO 14 DAY OUTLOOK FOR MAY 14 - 120 2002 MODEL COMPARISONS: MODEL AGREEMENT DECREASES SOMEWHAT FOR THIS PERIOD...BUT NOT UNUSUALLY SO. THE MRF AND MRF ENSEMBLE MEAN ARE IN REASONABLE AGREEMENT AND CONTINUE TO FORECAST A PATTERN SIMILAR TO THAT FOR THE 6 TO 10 DAY PERIOD... WITH SOMEWHAT LOWER HEIGHTS OVER THE EASTERN STATES THAN FOR THE 6 TO 10 DAY PERIOD AND WITH BELOW NORMAL HEIGHTS OVER NEW ENGLAND. THE DAVA HAS A FAIRLY STRONG MEAN TROUGH OVER EASTERN CANADA AND THE NORTHEASTERN U.S. DURING THIS PERIOD WHICH WOULD AGREE WITH SOLUTION OF THE EXPERIMENTAL VERSION OF THE MRF. THE MRF AND ENSEMBLE MEAN HAVE THIS TROUGH CENTERED FARTHER EAST...OFF THE CANADIAN COAST. THE POSITIVE HEIGHT ANOMALY OVER THE NORTHEASTERN PACIFIC IS FORECAST TO MOVE A BIT NORTHEASTWARD FROM ITS LOCATION FOR DAYS 6 TO 10 AND BE CENTERED NEAR 52N/160W WHICH HAS TELECONNECTIONS WHICH SUPPORT THE LOWERING OF HEIGHTS OVER THE NORTHEASTERN STATES. CONFIDENCE IS ABOUT 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 WAS COMPOSED OF 40 PERCENT OF THE ENSEMBLE MEAN CENTERED ON DAY 11...30 PERCENT OF THE OPERATIONAL MRF CENTERED ON DAY 11...20 PERCENT OF THE MOST RECENT 7 DAY OBSERVED 500 MB MEAN...AND 10 PERCENT OF THE DAVA CENTERED ON DAY 11. THE TEMPERATURE OUTLOOK IS BASED ON THE KLEIN AND NEURAL NET SPECIFICATIONS FROM THE OFFICIAL BLEND. THE PRECIPITATION FORECAST IS BASED ON SPECIFICATIONS FROM THE NEURAL NET FOR THE OFFICIAL HEIGHT PROG...BIAS-ADJUSTED OUTPUT FROM THE OPERATIONAL MRF CENTERED ON DAY 11...AND ANALOGS TO THE ENSEMBLE MEAN CENTERED ON DAY 11. 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:------------------------------------------------------ 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 MAY 16. 6 to 10 day Outlook Table STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN WASHINGTON B N OREGON B N NRN CALIF B A SRN CALIF B N IDAHO N N NEVADA N N W MONTANA B N E MONTANA B N WYOMING N N UTAH N N ARIZONA N N COLORADO A N NEW MEXICO A B N DAKOTA B A S DAKOTA N N NEBRASKA A N KANSAS A N OKLAHOMA A B N TEXAS A B S TEXAS A B W TEXAS A B MINNESOTA N A IOWA A N MISSOURI A A ARKANSAS A N LOUISIANA A B WISCONSIN N A ILLINOIS A A MISSISSIPPI A N MICHIGAN N A INDIANA A A OHIO A A KENTUCKY A A TENNESSEE A A ALABAMA A N NEW YORK N N VERMONT N N NEW HAMP N N MAINE N N MASS N N CONN N N RHODE ISL N N PENN A A NEW JERSEY A N W VIRGINIA A A MARYLAND A N DELAWARE A N VIRGINIA A A N CAROLINA A N S CAROLINA A N GEORGIA A N FL PNHDL A B FL PENIN A B AK N SLOPE N N AK ALEUTIAN A N AK WESTERN N A AK INT BSN B A AK S INT B N AK S COAST B N AK PNHDL B B 8 to 14 day Outlook Table STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN WASHINGTON B B OREGON B N NRN CALIF B N SRN CALIF B N IDAHO N N NEVADA N N W MONTANA B A E MONTANA B A WYOMING N N UTAH N N ARIZONA N N COLORADO A N NEW MEXICO A N N DAKOTA B N S DAKOTA B N NEBRASKA N N KANSAS A N OKLAHOMA A N N TEXAS A B S TEXAS A B W TEXAS A N MINNESOTA B A IOWA N A MISSOURI N N ARKANSAS A N LOUISIANA A B WISCONSIN N A ILLINOIS N A MISSISSIPPI A B MICHIGAN B A INDIANA N A OHIO N A KENTUCKY N A TENNESSEE A A ALABAMA A B NEW YORK B N VERMONT B N NEW HAMP B N MAINE B N MASS B N CONN B N RHODE ISL B N PENN N N NEW JERSEY B N W VIRGINIA N A MARYLAND N N DELAWARE N N VIRGINIA N N N CAROLINA A N S CAROLINA A N GEORGIA A N FL PNHDL A B FL PENIN A B AK N SLOPE N A AK ALEUTIAN A N AK WESTERN N N AK INT BSN N A AK S INT B B AK S COAST B B 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