PROGNOSTIC DISCUSSIONS FOR 6 TO 10 AND 8 TO 14 DAY OUTLOOKS CLIMATE PREDICTION CENTER NCEP NATIONAL WEATHER SERVICE WASHINGTON DC 3 PM EST FRI JAN 4 2002 6 TO 10 DAY OUTLOOK FOR JAN 10 - 14 2002 . . . . . . . . MODEL COMPARISONS: THE MAIN FORECAST CHALLENGE TODAY INVOLVES RESOLVING SEVERAL MEDIUM WAVELENGTH TROUGHS EMBEDDED WITHIN A BROAD MEAN TROUGH FROM SIBERIA TO EXTREME WESTERN ALASKA. THERE IS INCREASING AGREEMENT AMONGST THE MODEL GUIDANCE FOR A RE- ESTABLISHED PRESENCE OF THE BERING SEA TROUGH WHICH WILL LIKELY REINFORCE THE TENDENCY FOR COLD OVER AT LEAST FAR WESTERN PORTIONS OF ALASKA...AND POSSIBLY INTO THE CENTRAL THIRD OF THE STATE. THE DAVA SOLUTION IS THE MOST BULLISH ON THIS TROUGH WHEN COMPARED TO THE OTHER PRINCIPAL MODELS. AS FOR THE LOWER 48...THE PRINCIPAL ASSORTMENT OF MODEL SOLUTIONS TODAY CON- TINUE TO BE IN GOOD AGREEMENT ON AN AMPLIFIED MEAN RIDGE ALONG THE WEST COAST OF NORTH AMERICA...AND A TROUGH CENTERED OVER THE EASTERN U.S. THIS POSITIVELY PHASED PNA (PACIFIC NORTH AMERICAN) PATTERN IS SUPPORTED BY THE HIGH RESOLUTION MRF - THE ENSEMBLE AVERAGE - THE DAVA (DIVERGENT ANOMALY VORTICITY ADVECTION) MODEL - AND THE ECMWF SOLUTION...WITH THE DAVA STILL PREDICTING A MORE POSI- TIVELY SLOPED TROUGH FROM THE EASTERN GREAT LAKES REGION SOUTHWESTWARD INTO THE SOUTHERN PLAINS/SOUTHERN ROCKIES. . . . . . . . . CONFIDENCE IN TODAYS FORECAST IS RATED AS ABOVE AVERAGE... 4 ON A 1-5 SCALE... LARGELY DUE TO GOOD NUMERICAL MODEL AGREEMENT AND DAY-TO-DAY CONTINUITY...BUT SOMEWHAT REDUCED OVER THE ALASKAN SECTOR. THE OFFICIAL 500 HPA HEIGHT FORECAST FOR THE 6 TO 10 DAY PERIOD USES 30 PERCENT OF TODAYS MRF ENSEMBLE MEAN CENTERED ON DAY 8... 30 PERCENT OF TODAYS DAVA SOL- UTION CENTERED ON DAY 8... 20 PERCENT OF TODAYS HIGH RESOLUTION MRF CENTERED ON DAY 8... AND 20 PERCENT OF TODAYS ECMWF MODEL CENTERED ON DAY 7. . . . . . . . . MODEL OF THE DAY: MRF ENSEMBLE AND DAVA THE TEMPERATURE PROG IS BASED PRIMARILY ON A CONSENSUS BETWEEN THE KLEIN OBJEC- TIVE SPECIFICATIONS FROM THE BLEND...AND ALSO FROM THE DAVA - THE MRF - AND ECMWF MODELS. THE ANOMALOUS WARMTH EXPECTED OVER MUCH OF THE NORTHEAST U.S. IS ATTRIBUTED TO EASTERLY ANOMALOUS FLOW OF MODIFIED ATLANTIC AIR. THE LACK OF BITTER COLD DRY AIR...ALONG WITH THE INCREASED MOISTURE CONTENT FROM THE ATLANTIC...SHOULD PRIMARILY CONTRIBUTE TO ELEVATED OVERNIGHT MINIMUM TEMPERA- TURES. THE PRECIPITATION PROG IS BASED MOSTLY ON THE ACCUMULATED MRF MODEL PRECIPITA- TION CORRECTED FOR RECENT BIASES...AND IS CONSISTENT WITH THE PREDICTED STORM TRACKS SHOWN BY THE MRF. 8 TO 14 DAY OUTLOOK FOR JAN 12 - 18 2002 . . . . . . . . TODAYS WEEK 2 MRF AND ENSEMBLE MEAN ARE IN REASONABLY GOOD AGREEMENT...THOUGH THE MRF SOLUTION IS NOW SUGGESTING THAT THE WESTERN U.S. RIDGE MAY MOVE SLIGHT- LY EASTWARD ESPECIALLY AT HIGHER LATITUDES...WHILE THE MID-LATITUDE PORTION OF THE RIDGE ACTUALLY RETROGRADES. THE 500 HPA HEIGHTS ARE EXPECTED TO LOWER OVER MUCH OF THE WEST...WHICH WOULD RESULT IN COOLER TEMPERATURES ACROSS THIS REG- ION. OVER THE EASTERN STATES...THE ENSEMBLE MEAN STEADFASTLY MAINTAINS THE TROUGH AXIS NEAR THE APPALACHIANS...WHILE THE SINGLE MRF RUN TRIES TO ADVANCE IT TO THE ATLANTIC COAST. CONFIDENCE IS THOUGHT TO BE NEAR AVERAGE TODAY...RATED 3 ON A SCALE OF 1-5. THE BLENDED 500 HPA HEIGHT PATTERN USES 60 PERCENT OF TODAYS MRF ENSEMBLE MEAN CENTERED ON DAY 11... AND 40 PERCENT OF TODAYS MRF MODEL CENTERED ON DAY 11. THE TEMPERATURE OUTLOOK IS BASED MAINLY ON A CONSENSUS OF THE KLEIN AND NEURAL NET SPECIFICATIONS FROM THE OFFICIAL HEIGHT PROG...AND ALSO FROM THE KLEINS OPERATING OFF THE MRF AND ENSEMBLE MEAN MODELS. THE PRECIPITATION FORECAST IS BASED PRIMARILY ON THE ACCUMULATED MRF MODEL PRECIPITATION OUTPUT CORRECTED FOR RECENT BIASES...AND IS GENERALLY CONSISTENT WITH THE EXPECTED STORM TRACKS. IF THE ENSEMBLE MEAN IS CORRECT IN HOLDING THE TROUGH BACK OVER THE APPALACHIANS...THEN THE ATLANTIC COASTAL AREAS MAY HAVE TO CONTEND WITH WINTRY PRECIPITATION DURING THIS PERIOD. IF THE MRF IS CORRECT...ANY POTENTIAL WINTER STORMS WOULD KEEP MOST...IF NOT ALL...OF THEIR ATTENDANT PRECIPITATION OUT TO SEA. 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. AVN - THE RUN OF THE MRF MODEL INITIATED AT 12 UTC. BLEND - A WEIGHTED AVERAGE OF FORECAST MODEL 500 HPA HEIGHT FORECAST MAPS. 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. 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 NON-DIVERGENT 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. EASTERLY WIND - WIND BLOWING FROM EAST TO WEST. 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. 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 LARGE SOUTHERLY AND NORTHERLY FLOW. MJO - MADDEN-JULIAN OSCILLATION - ALSO CALLED TROPICAL INTRA-SEASONAL OSCILLATION. 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. NAO - NORTH ATLANTIC OSCILLATION TELECONNECTION PATTERN. NORTHERLY WIND - WIND BLOWING FROM NORTH TO SOUTH 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. SOUTHERLY WIND - WIND BLOWING FROM SOUTH TO NORTH. 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. 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 A N OREGON N B NRN CALIF A B SRN CALIF A B IDAHO A B NEVADA N B W MONTANA A B E MONTANA A B WYOMING A B UTAH N B ARIZONA A B COLORADO A B NEW MEXICO N B N DAKOTA A N S DAKOTA A B NEBRASKA A B KANSAS A B OKLAHOMA A B N TEXAS A B S TEXAS N B W TEXAS N B MINNESOTA A N IOWA A N MISSOURI A N ARKANSAS N B LOUISIANA N B WISCONSIN A N ILLINOIS A N MISSISSIPPI N B MICHIGAN A N INDIANA N N OHIO A N KENTUCKY N N TENNESSEE N N ALABAMA B B NEW YORK A N VERMONT A A NEW HAMP A A MAINE A A MASS A A CONN A N RHODE ISL A A PENN A N NEW JERSEY A N W VIRGINIA N N MARYLAND N N DELAWARE N N VIRGINIA N N N CAROLINA N B S CAROLINA B B GEORGIA B B FL PNHDL B B FL PENIN B N AK N SLOPE N B AK ALEUTIAN B A AK WESTERN B A AK INT BSN N B AK S INT A N AK S COAST A A AK PNHDL A N 8 to 14 day Outlook Table STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN WASHINGTON N N OREGON B B NRN CALIF B B SRN CALIF B B IDAHO N B NEVADA B B W MONTANA N B E MONTANA A B WYOMING N B UTAH N B ARIZONA N N COLORADO N B NEW MEXICO N A N DAKOTA A N S DAKOTA A B NEBRASKA N B KANSAS N B OKLAHOMA N B N TEXAS N B S TEXAS N B W TEXAS N B MINNESOTA A A IOWA N N MISSOURI N B ARKANSAS N B LOUISIANA B N WISCONSIN N A ILLINOIS N B MISSISSIPPI B B MICHIGAN N N INDIANA B B OHIO B B KENTUCKY B B TENNESSEE B B ALABAMA B B NEW YORK N N VERMONT A A NEW HAMP A A MAINE A A MASS N N CONN N N RHODE ISL N N PENN B B NEW JERSEY B N W VIRGINIA B B MARYLAND B B DELAWARE B B VIRGINIA B B N CAROLINA B B S CAROLINA B B GEORGIA B B FL PNHDL B B FL PENIN B B AK N SLOPE N B AK ALEUTIAN B A AK WESTERN B N AK INT BSN N N AK S INT A A AK S COAST A A AK PNHDL A N 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