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 13 2002 6 TO 10 DAY OUTLOOK FOR MAY 19 - 23 2002 . . . . . . . . MODEL COMPARISONS: MODELS ARE IN REASONABLY GOOD AGREEMENT TODAY OVER THE NORTH AMERICAN SECTOR. THE KEY LARGE-SCALE FEATURES OF THE 500 HPA CIRCULA- TION INCLUDE A MEAN RIDGE OVER THE EASTERN PACIFIC AND GULF OF ALASKA REGION ...A TROUGH ALONG THE U.S. WEST COAST...WEAK RIDGING OVER THE NATIONS HEART- LAND...A TROUGH OVER THE NORTHEASTERN U.S. AND CANADIAN MARITIMES REGION... AND HIGH LATITUDE BLOCKING FROM ALASKA TO GREENLAND. A WELL DEFINED NEGATIVE PHASE OF THE NORTH ATLANTIC OSCILLATION (NAO) IS ALSO FORECAST...WITH WELL ABOVE NORMAL HEIGHTS OVER GREENLAND AND AN UNDERCUTTING ZONE OF BELOW NORMAL HEIGHTS OVER THE MID-TO-HIGH LATITUDE ATLANTIC. CONFIDENCE TODAY IS RATED AS ABOVE AVERAGE...4 ON A SCALE OF 1 TO 5. THE OFFICIAL 500-HPA HEIGHT FORECAST FOR THE 6 TO 10 DAY PERIOD IS COMPOSED OF 35 PERCENT OF THE ENSEMBLE MEAN CENTERED ON DAY 8... 35 PERCENT OF TODAYS DAVA RUN CENTERED ON DAY 8... 15 PERCENT OF TODAYS MRF CENTERED ON DAY 8... AND 15 PERCENT OF TODAYS ECMWF SOLUTION CENTERED ON DAY 7. MODEL OF THE DAY: MRF ENSEMBLE MEAN AND DAVA THE TEMPERATURE PROG IS BASED ON KLEIN AND NEURAL NET SPECIFICATIONS FROM THE OFFICIAL 500 HPA HEIGHT PROG...THE ANALOGS FROM THE MRF ENSEMBLE MEAN AND DAVA...MOS OUTPUT FROM THE ENSEMBLES...AND A SUBJECTIVE INTERPRETATION OF THE DAILY MRF MAPS OF SURFACE FEATURES. THE PRECIPITATION PROG IS BASED ON MRF MODEL PRECIPITATION...THE NEURAL NET SPECIFICATIONS FROM THE OFFICIAL HEIGHT PROG...AND ANALOGS FROM THE VARIOUS MODELS. . . . . . . . . 8 TO 14 DAY OUTLOOK FOR MAY 21 - 27 2002 MODEL COMPARISONS: FOR THIS PERIOD...THE MRF AND ENSEMBLE MEAN D+11 CIRCULA- TION FORECASTS FAVOR A MERIDIONAL PATTERN OVER NORTH AMERICA...WHILE THE DAVA TAKES A MORE ZONAL APPROACH. THE GULF OF ALASKA RIDGE IS PERSISTED BY ALL THREE MODEL SOLUTIONS...AND SHOULD KEEP MOST OF ALASKA ON THE WARM SIDE. THE CONSENSUS OF THESE THREE NUMERICAL SOLUTIONS FAVORS SOME ENERGY FROM THE U.S. WEST COAST TROUGH TO PUSH INLAND ACROSS THE SOUTHWESTERN DESERTS...WHILE THE NORTHEASTERN TROUGH GRADUALLY LIFTS OUT TOWARDS THE SOUTHERN MARITIMES. CONFIDENCE IS SLIGHTLY BELOW AVERAGE FOR A WEEK TWO FORECAST AT THIS TIME OF YEAR...RATED 2 ON A SCALE FROM 1 TO 5. THE OFFICIAL 500 MB HEIGHT FORECAST FOR THE 8 TO 14 DAY PERIOD IS COMPOSED OF 40 PERCENT OF THE ENSEMBLE MEAN CENTERED ON DAY 11... 40 PERCENT OF TODAYS DAVA SOLUTION CENTERED ON DAY 11...AND 20 PERCENT OF TODAYS MRF CENTERED ON DAY 11. THE TEMPERATURE OUTLOOK IS BASED ON THE KLEIN AND NEURAL NET SPECIFICATIONS FROM THE OFFICIAL HEIGHT PROG...AND ANALOGS FROM THE MRF ENSEMBLE MEAN AND DAVA MODELS. THE PRECIPITATION FORECAST IS BASED ON SPECIFICATIONS FROM THE NEURAL NET FROM THE OFFICIAL HEIGHT PROG...AND ANALOGS TO THE ENSEMBLE MEAN AND DAVA RUNS. FORECASTER: A. ARTUSA . . . . . . . . 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 A OREGON B A NRN CALIF B A SRN CALIF B N IDAHO N A NEVADA B A W MONTANA B A E MONTANA N A WYOMING N N UTAH N B ARIZONA N B COLORADO N B NEW MEXICO A B N DAKOTA B A S DAKOTA N A NEBRASKA N A KANSAS N A OKLAHOMA N A N TEXAS A A S TEXAS A N W TEXAS A N MINNESOTA B N IOWA N A MISSOURI N A ARKANSAS N A LOUISIANA A N WISCONSIN B N ILLINOIS B N MISSISSIPPI A A MICHIGAN B N INDIANA B N OHIO B N KENTUCKY N N TENNESSEE N A ALABAMA A A NEW YORK B B VERMONT B N NEW HAMP B N MAINE B A MASS B B CONN B B RHODE ISL B B PENN B B NEW JERSEY B B W VIRGINIA B B MARYLAND B B DELAWARE B B VIRGINIA B B N CAROLINA N N S CAROLINA N N GEORGIA N A FL PNHDL A N FL PENIN A N AK N SLOPE A B AK ALEUTIAN A A AK WESTERN A A AK INT BSN A B AK S INT A N AK S COAST A N AK PNHDL A B 8 to 14 day Outlook Table STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN WASHINGTON B A OREGON B A NRN CALIF B A SRN CALIF B N IDAHO B A NEVADA B N W MONTANA B A E MONTANA B A WYOMING N N UTAH N N ARIZONA N B COLORADO N B NEW MEXICO N B N DAKOTA B A S DAKOTA N N NEBRASKA N N KANSAS N N OKLAHOMA A B N TEXAS A B S TEXAS A B W TEXAS A B MINNESOTA N A IOWA N N MISSOURI N N ARKANSAS N B LOUISIANA A B WISCONSIN N A ILLINOIS N A MISSISSIPPI A B MICHIGAN N A INDIANA N A OHIO N A KENTUCKY N N TENNESSEE N N 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 B N NEW JERSEY B N W VIRGINIA N N MARYLAND B N DELAWARE B N VIRGINIA N N N CAROLINA N N S CAROLINA N B GEORGIA N B FL PNHDL A B FL PENIN N B AK N SLOPE A N AK ALEUTIAN A A AK WESTERN A A AK INT BSN A N AK S INT A N AK S COAST A N AK PNHDL A B LEGEND TEMPS WITH RESPECT TO NORMAL PCPN WITH RESPECT TO MEDIAN A - ABOVE N - NEAR NORMAL A - ABOVE N - NEAR MEDIAN N - NEAR NORMAL 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