PROGNOSTIC DISCUSSIONS FOR 6 TO 10 AND 8 TO 14 DAY OUTLOOKS CLIMATE PREDICTION CENTER NCEP NATIONAL WEATHER SERVICE WASHINGTON DC 3 PM EDT TUES MAY 7 2002 6 TO 10 DAY OUTLOOK FOR MAY 13 - 17 2002 . . . . . . . . MODEL COMPARISONS: MODELS ARE IN GOOD AGREEMENT TODAY FOR THE FIRST THREE TO FOUR DAYS BUT START TO DIVERGE NOTICEABLY ON THE STRENGTH AND TIMING OF A TROUGH OVER THE MIDDLE OF THE NATION ON DAY 5. THE DAILY SOLUTIONS FROM THE ECMWF AND MRF ENSEMBLE MEMBERS FOR DAYS 6 THROUGH 10 SHOW A LARGE SPREND OVER THE PACIFIC WITH LESS SPREAD OVER THE NORTH AMERICAN CONTINENT...BUT EVEN THE SPREAD OVER THE CONTINENT IMPLIES SIGNIFICANT UNCERTAINTY IN THE TIMING OF SHORT WAVES AND THEREFORE THE DAILY WEATHER AT ANY LOCATION. THE 6 TO 10 DAY MEANS HAVE CHANGED SOMEWHAT FROM YESTERDAY. THE ECMWF HAS MADE THE BIGGEST SWITCH OVER THE U.S. ...HAVING GONE FROM A BASICALLY ZONAL FLOW WITH ENHANCED JET STREAM YESTERDAY TO A HIGHLY AMPLIFIED SOLUTION WITH FULL LATITUDE RIDGE OVER WESTERN NORTH AMERICA AND A FULL LATITUDE TROUGH FROM THE CANADIAN ARCHIPELAGO TO THE BAHAMAS TODAY. THE 6 TO 10 MRF...MRF ENSEMBLE MEAN...AND DAVA ARE IN MUCH BETTER AGREEMENT WITH THEIR SOLUTIONS FROM YESTERDAYS RUNS... WITH A SLIGHT EASTWARD PROGRESSION OF THE WEAK MEAN WESTERN TROUGH AND A WEAKENING OF THE RIDGE OVER THE SOUTHEASTERN STATES. THE ECMWF SOLUTION IS PRACTICALLY A COMPLETE REVERSAL OF THE RECENT OBSERVED PATTERN OVER THE U.S. IT IS SOMEWHAT LIKE THE WEEK TWO MRF ENSEMBLE MEAN AND DAVA SOLUTIONS TODAY. PERHAPS THE ECMWF IS HINTING AT A NEW REGIME AND IS TOO QUICK TO MAKE THE TRANSITION...OR PERHAPS THE OTHER MODELS ARE TOO SLOW. THE ECMWF SOLUTION DOES NOT TELECONNECT WELL THOUGH. THE STRONG POSITIVE HEIGHT ANOMALY THAT THE ECMWF FORECASTS NEAR 60N/160W SUGGESTS A DOWNSTREAM PATTERN WITH BELOW NORMAL HEIGHTS OVER MOST OF CANADA AND THE NORTHERN U.S. AND ABOVE NORMAL HEIGHTS OVER THE SOUTHERN U.S. THIS WOULD BE MORE CONSISTENT WITH AN ENHANCED ZONAL FLOW THAN THE HIGH AMPLITUDE WAVE PATTERN OF THE ECMWF SOLUTION. HOWEVER THE DOWNSTREAM TELECONNECTION PATTERN IS NOT STATISTICALLY SIGNIFICANT. THE OVERALL PATTERN FORECASTED OVER NORTH AMERICA BY THE OFFICIAL HEIGHT PROG CONTINUES TO BE BELOW NORMAL HEIGHTS OVER MOST OF CANADA AND THE NORTHWESTERN STATES AND ABOVE NORMAL HEIGHTS OVER THE SOUTHERN TWO THIRDS OF THE LOWER 48 STATES...FAIRLY SIMILAR TO THE MOST RECENT OBSERVED 5 DAY MEAN PATTERN BUT WITH WEAKER ANOMALIES. THE OFFICIAL HEIGHT PROG HAS A STRONG POSITIVE ANOMALY CENTERED AT 55N/165W WHICH TELECONNECTS WELL WITH THE DOWNSTREAM PATTERN IN THE OFFICIAL HEIGHT PROG. CONFIDENCE IN THE FORECAST TODAY IS BELOW AVERAGE...RATED 2 ON A SCALE FROM 1 TO 5...DUE TO SOME MODEL DISAGREEMENT AND LOWER RUN-TO-RUN CONSISTENCY. THE OFFICIAL 500-MB HEIGHT FORECAST FOR THE 6 TO 10 DAY PERIOD WAS COMPOSED OF 10 PERCENT OF THE ECMWF CENTERED ON DAY 7...30 PERCENT OF THE OPERATIONAL MRF CENTERED ON DAY 8...40 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. MODEL OF THE DAY: MRF ENSEMBLE MEAN THE TEMPERATURE PROG IS BASED ON KLEIN AND NEURAL NET SPECIFICATIONS FROM THE OFFICIAL 500 MB HEIGHT PROG. THE PRECIPITATION PROG IS BASED ON MRF AND BIAS-ADJUSTED OPERATIONAL MRF OUTPUTS...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 15 - 21 2002 MODEL COMPARISONS: MODEL AGREEMENT IS REASONABLE FOR THIS PERIOD...WITH THE MRF AND MRF ENSEMBLE MEAN BEING FAIRLY SIMILAR AND THE DAVA NOT TOO DIFFERENT. THE DAVA ESPECIALLY GOES TOWARD THE 6 TO 10 DAY ECMWF MEAN BUT WITH WEAKER ANOMALIES. THE POSITIVE HEIGHT ANOMALY OVER THE NORTHEASTERN PACIFIC IS FORECAST TO BE CENTERED NEAR 55N/165W WHICH HAS TELECONNECTIONS WHICH SUPPORT THE OFFICIAL HEIGHT PROG PATTERN OVER NORTH AMERICA. 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...20 PERCENT OF THE OPERATIONAL MRF CENTERED ON DAY 11...10 PERCENT OF THE YESTERDAYS MRF ENSEMBLE MEAN CENTERED ON DAY 10...10 PERCENT OF THE ECMWF CENTERED ON DAY 7...AND 20 PERCENT OF THE DAVA CENTERED ON DAY 11. THE TEMPERATURE OUTLOOK IS BASED ON THE KLEIN AND NEURAL NET SPECIFICATIONS FROM THE OFFICIAL HEIGHT PROG. THE PRECIPITATION FORECAST IS BASED ON SPECIFICATIONS FROM THE NEURAL NET FROM 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 N SRN CALIF B N IDAHO B N NEVADA N N W MONTANA B N E MONTANA B N WYOMING N A UTAH N A ARIZONA N N COLORADO N N NEW MEXICO A N N DAKOTA B N S DAKOTA N A NEBRASKA N N KANSAS N N OKLAHOMA A N N TEXAS A N S TEXAS A B W TEXAS A N MINNESOTA B A IOWA N A MISSOURI N A ARKANSAS A A LOUISIANA A B WISCONSIN N A ILLINOIS N A MISSISSIPPI A N MICHIGAN B A INDIANA N A OHIO N A KENTUCKY N A TENNESSEE A A ALABAMA A N NEW YORK N N VERMONT B N NEW HAMP B N MAINE B N MASS N N CONN N N RHODE ISL N N PENN N N NEW JERSEY N 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 A AK INT BSN B A AK S INT B B AK S COAST N B AK PNHDL B B 8 to 14 day Outlook Table STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN WASHINGTON B B OREGON B B NRN CALIF B N SRN CALIF B N IDAHO N B NEVADA N N W MONTANA B B E MONTANA B N WYOMING N B UTAH N B ARIZONA N N COLORADO N N NEW MEXICO A N N DAKOTA B N S DAKOTA B N NEBRASKA N N KANSAS N N OKLAHOMA A A N TEXAS A A S TEXAS A N W TEXAS A N MINNESOTA B N IOWA B A MISSOURI N A ARKANSAS A A LOUISIANA A A WISCONSIN B A ILLINOIS N A MISSISSIPPI A A MICHIGAN B N INDIANA N A OHIO N N KENTUCKY N N TENNESSEE N N ALABAMA A N NEW YORK B N VERMONT B N NEW HAMP B N MAINE B N MASS B B CONN B B RHODE ISL B B PENN B N NEW JERSEY B B W VIRGINIA N N MARYLAND N B DELAWARE N B VIRGINIA N N N CAROLINA N N S CAROLINA N N GEORGIA A N FL PNHDL A N FL PENIN A N AK N SLOPE N A AK ALEUTIAN A B AK WESTERN N N AK INT BSN B A AK S INT B B AK S COAST N 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