PROGNOSTIC DISCUSSIONS FOR 6 TO 10 AND 8 TO 14 DAY OUTLOOKS CLIMATE PREDICTION CENTER NCEP NATIONAL WEATHER SERVICE WASHINGTON DC 3 PM EST MON JAN 21 2002 6 TO 10 DAY OUTLOOK FOR JAN 27 - 31 2002 . . . . . . . . MODEL COMPARISONS: MRF... MRF ENSEMBLE MEAN... ECMWF AND DAVA ALL ARE IN GOOD AGREEMENT AND PREDICT A STRONGLY AMPLIFIED PATTERN WITH A 500 HPA NEGATIVE ANOMALY OVER THE WESTERN U.S. AND A POSITIVE ANOMALY OVER THE EAST. THE ENSEMBLE MEAN IS THE LEAST AMPLIFIED AS USUAL AND THE ECMWF HAS THE STRONGEST ANOMALIES. ALL MODELS NOW PREDICT A NORTHWARD CONTRACTION OF THE JET IN THE NORTHERN NORTH PACIFIC WITH POSITIVE ANOMALIES COVERING ALL THE MIDDLE LATITUDES. THE MODELS ALSO SHOW A SMALL AREA OF BLOCKING AROUND BAFFIN ISLAND AND NORTHERN GREENLAND BUT IT IS NOT EXTENSIVE ENOUGH TO PUSH THE POLAR VORTEX FURTHER SOUTH THAN NORTH-CENTRAL CANADA... AND THE COLDEST AIR REMAINS IN CENTRAL AND SOUTHERN CANADA MOST OF THE IIME WITH ONLY BRIEF EXCURSIONS INTO AND ACROSS THE NORTH-CENTRAL PART OF THE CONUS. . . . . . . . . CONFIDENCE IN TODAYS FORECAST IS WELL ABOVE AVERAGE... 5 ON A 1-5 SCALE. THE OFFICIAL 500 HPA HEIGHT FORECAST FOR THE 6 TO 10 DAY PERIOD USES 50 PERCENT OF TODAYS MRF ENSEMBLE MEAN CENTERED ON DAY 8... 15 PERCENT OF TODAYS OPERATIONAL MRF CENTERED ON DAY 8... 20 PERCENT OF TODAYS DAVA CENTERED ON DAY 8... AND 15 PERCENT OF TODAYS ECMWF CENTERED ON DAY 7. . . . . . . . . MODEL OF THE DAY: MRF ENSEMBLE MEAN THE TEMPERATURE PROG IS BASED PRIMARILY ON THE KLEIN AMD THE MEURAL NET TEMPERATURE SPECIFICATIONS FROM THE 500 HPA BLEND. THE PRECIPITATION PROG IS BASED MOSTLY ON THE NEURAL NET FROM THE OFFICIAL 500 HPA BLEND... MODEL OUTPUT CORRECTED FOR RECENT MEAN ERRORS... AND COMPOSITE PATTERNS OF THE PAST BEST ANALOGS TO THE HEIGHT FORECAST. 8 TO 14 DAY OUTLOOK FOR JAN 29 - FEB 04 2002 MODEL COMPARISONS: MRF... MRF ENSEMBLE AND DAVA FORECASTS ARE SIMILAR TO DE-AMPLIFIED VERSIONS OF THE 6-10 DAY FORECASTS. MODELS... ESPECIALLY THE ENSEMBLE MEAN... PREDICT SOME PROGRESSION OF THE PATTERN WITH THE TROUGH MOVING FROM THE WEST INTO THE HIGH PLAINS. THIS WOULD ALLOW ARCTIC AIR TO ENTER THE MIDDLE OF THE COUNTRY MORE EMPHATICALLY... AND THE DAILY MRF FORECAST MAPS AT THIS RANGE AGREE THAT SOME OF THE ARCTIC AIR IS LIKELY TO SIGNIFICANTLY AFFECT AT LEAST MOST OF THE GREAT PLAINS AND MISSISSIPPI VALLEY. . . . . . . . . CONFIDENCE IN TODAYS FORECAST IS ABOVE AVERAGE FOR THIS RANGE... RATED 4 ON A SCALE OF 1-5. THE OFFICIAL 500 HPA HEIGHT FORECAST FOR THE 8 TO 14 DAY PERIOD USES 40 PERCENT OF TODAYS MRF ENSEMBLE MEAN CENTERED ON DAY 11... 10 PERCENT OF TODAYS OPERATIONAL MRF CENTERED ON DAY 11... 20 PERCENT OF TODAYS DAVA CENTERED ON DAY 11... AND 10 PERCENT EACH OF TODAYS ECMWF 5 DAY MEAN CENTERED ON DAY 7... TODAYS MRF WEEKLY MEAN CENTERED ON DAY 7... AND TODAYS WEEKLY ENSEMBLE MEAN CENTERED ON DAY 7. THE TEMPERATURE OUTLOOK IS BASED MAINLY ON A CONSENSUS OF THE KLEIN AND NEURAL NET SPECIFICATIONS FROM THE OFFICIAL BLEND. THE PRECIPITATION FORECAST IS BASED PRIMARILY ON THE BAIS CORRECTED ACCUMULATED MRF ENSEMBLE OUTPUT... THE NERUAL NET FROM THE 500 HPA BLEND... AND COMPOSITE PATTERNS OF THE PAST BEST ANALOGS TO THE OFFICIAL HEIGHT FORECAST. 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 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. 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. 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 JANUARY 17. 6 to 10 day Outlook Table STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN WASHINGTON B A OREGON B A NRN CALIF B N SRN CALIF B B IDAHO B A NEVADA B N W MONTANA N A E MONTANA N N WYOMING N N UTAH B N ARIZONA B B COLORADO N N NEW MEXICO N B N DAKOTA N N S DAKOTA N N NEBRASKA N N KANSAS A N OKLAHOMA A N N TEXAS A N S TEXAS A N W TEXAS N B MINNESOTA N N IOWA A N MISSOURI A N ARKANSAS A A LOUISIANA A A WISCONSIN A N ILLINOIS A N MISSISSIPPI A A MICHIGAN A N INDIANA A N OHIO A N KENTUCKY A N TENNESSEE A A ALABAMA A A NEW YORK A N VERMONT N N NEW HAMP N N MAINE N N MASS N A CONN N A RHODE ISL N A PENN A N NEW JERSEY A A W VIRGINIA A A MARYLAND A A DELAWARE A A VIRGINIA A A N CAROLINA A A S CAROLINA A A GEORGIA A A FL PNHDL A A FL PENIN A A AK N SLOPE B N AK ALEUTIAN B N AK WESTERN B N AK INT BSN B N AK S INT B N AK S COAST B B AK PNHDL B 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 B IDAHO B A NEVADA B N W MONTANA N A E MONTANA N N WYOMING N N UTAH N N ARIZONA B B COLORADO N B NEW MEXICO N B N DAKOTA N N S DAKOTA N N NEBRASKA A B KANSAS A B OKLAHOMA A A N TEXAS A A S TEXAS A N W TEXAS A B MINNESOTA N N IOWA N B MISSOURI A B ARKANSAS A A LOUISIANA A A WISCONSIN N N ILLINOIS A B MISSISSIPPI A A MICHIGAN N N INDIANA A B OHIO A N KENTUCKY A N TENNESSEE A A ALABAMA A A NEW YORK N N VERMONT N N NEW HAMP N A MAINE B N MASS N A CONN N A RHODE ISL N A PENN A A NEW JERSEY A A W VIRGINIA A A MARYLAND A A DELAWARE A A VIRGINIA A A N CAROLINA A A S CAROLINA A A GEORGIA A A FL PNHDL A A FL PENIN A N AK N SLOPE B N AK ALEUTIAN B N AK WESTERN B N AK INT BSN B N AK S INT B N AK S COAST B N 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 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