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 11 2002 6 TO 10 DAY OUTLOOK FOR JAN 17 - 21 2002 . . . . . . . . MODEL COMPARISONS: MODELS REMAIN IN FAIRLY GOOD AGREEMENT ON THE MAJOR FEATURES... WITH THE LARGE CYCLONIC VORTEX CENTERED NORTH OF HUDSON BAY AND A FULL-LATITUDE TROUGH EXTENDING SOUTHWARD IN THE CENTRAL U.S. A LARGE RIDGE WILL DOMINATE THE GULF OF ALASKA. THE MODELS DIFFER ON THE DETAILS OF THE STRENGTH OF THESE FEATURES... BUT THE OPERATIONAL MRF IS IN GOOD AGREEMENT WITH THE BULK OF THE MRF ENSEMBLE MEMBERS... PERHAPS DIGGING THE TROUGH TOO DEEPLY INTO THE CENTRAL U.S. NEAR THE START OF THE FORECAST PERIOD... A FRONTAL SYSTEM EXITS THE EAST COAST AS COLD AIR DOMINATES MUCH OF THE NATION. THE NEW 12Z AVNX SHOWS A SHORT WAVE DIVING SOUTHWARD ALONG THE WEST COAST ON JANUARY 17-18... AND THIS COULD TRIGGER A STORM SYSTEM WITH WIDESPREAD RAIN AND SNOW DURING THE NEXT SEVERAL DAYS... ESPECIALLY OVER THE NORTHERN HALF OF THE COUNTRY. OTHER SHORT WAVES ALSO ORIGINATING OVER THE PACIFIC WILL ROTATE AROUND THE MEAN TROUGH AND HAVE THE POTENTIAL TO TRIGGER WET LOW PRESSURE SYSTEMS AT THE SURFACE. AS USUAL... TRYING TO TIME AND LOCATE THE AREAS OF HEAVIEST RAIN OR SNOW BEYOND THE NEXT FEW DAYS IS A CHALLENGE. . . . . . . . . CONFIDENCE IN TODAYS FORECAST IS RATED AS AVERAGE... 3 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... 25 PERCENT OF TODAYS OPERATIONAL MRF CENTERED ON DAY 8... AND 15 PERCENT OF TODAYS DAVA CENTERED ON DAY 8... AND 10 PERCENT OF YESTERDAYS ECMWF CENTERED ON DAY 7. . . . . . . . . MODEL OF THE DAY: OPERATIONAL MRF THE TEMPERATURE PROG IS BASED PRIMARILY ON THE KLEIN SPECIFICATIONS FROM THE 500 HPA BLEND AND THE COMPOSITE ANALOGUE FROM THE MRF ENSEMBLE. THE PRECIPITATION PROG IS BASED MOSTLY ON THE NEURAL NET FROM THE OFFICIAL 500 HPA BLEND AND THE COMPOSITE ANALOGUE. 8 TO 14 DAY OUTLOOK FOR JAN 19 - 25 2002 . . . . . . . . TODAYS WEEK 2 MRF AND ENSEMBLE MEAN SHOW THE CYCLONIC VORTEX PERSISTING NEAR BAFFIN ISLAND AND A MEAN TROUGH EXTENDING SOUTHWARD INTO THE CENTRAL AND EASTERN U.S. SHORT WAVES ROTATING AROUND THE WESTERN EDGE OF THE TROUGH CARVE OUT A VERY LARGE FULL LATITUDE TROUGH ACROSS NORTH AMERICA. THE MRF OPERATIONAL MODEL APPEARS TO OVER-AMPLIFY THE TROUGH OVER THE U.S... SO THE WEAKER DAVA MODEL IS PREFERRED. NEVERTHELESS... THE PATTERN SUGGESTS A STORMY AND COLD PATTERN FOR MUCH OF THE NORTHERN HALF OF THE COUNTRY WITH THE CONTINUING POTENTIAL FOR EAST COAST LOWS TO DEVELOP AND TRACK NORTHWARD. CONFIDENCE IS THOUGHT TO BE BELOW AVERAGE TODAY...RATED 2 ON A SCALE OF 1-5. THE BLENDED 500 HPA HEIGHT PATTERN USES 60 PERCENT OF TODAYS MRF ENSEMBLE MEAN CENTERED ON DAY 11... 30 PERCENT OF TODAYS DAVA MODEL CENTERED ON DAY 11... AND 10 PERCENT OF TODAYS MRF MODEL CENTERED ON DAY 11. THE TEMPERATURE OUTLOOK IS BASED MAINLY ON A CONSENSUS OF THE KLEIN SPECIFICATIONS FROM THE OFFICIAL BLEND AND THE 850 HPA TEMPERATURE FROM THE MRF ENSEMBLE. THE PRECIPITATION FORECAST IS BASED PRIMARILY ON THE ACCUMULATED MRF ENSEMBLE OUTPUT AND THE NERUAL NET FROM THE 500 HPA BLEND. FORECASTER: D. LE COMTE . . . . . . . . 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 B B OREGON B B NRN CALIF B B SRN CALIF B B IDAHO B A NEVADA B B W MONTANA B A E MONTANA N A WYOMING B A UTAH B N ARIZONA B N COLORADO B N NEW MEXICO B N N DAKOTA N A S DAKOTA N A NEBRASKA B A KANSAS B N OKLAHOMA B N N TEXAS B N S TEXAS B N W TEXAS B N MINNESOTA N A IOWA B A MISSOURI B N ARKANSAS B N LOUISIANA B N WISCONSIN B A ILLINOIS B N MISSISSIPPI B N MICHIGAN B A INDIANA B N OHIO B N KENTUCKY B N TENNESSEE B N ALABAMA B 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 B N NEW JERSEY N N W VIRGINIA B N MARYLAND B N DELAWARE B N VIRGINIA B N N CAROLINA B N S CAROLINA B N GEORGIA B N FL PNHDL N N FL PENIN N N AK N SLOPE N A AK ALEUTIAN N A AK WESTERN N A AK INT BSN A A AK S INT A A AK S COAST A A AK PNHDL N N 8 to 14 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 B A E MONTANA B A WYOMING B A UTAH B N ARIZONA B B COLORADO N N NEW MEXICO N B N DAKOTA B A S DAKOTA N N NEBRASKA N N KANSAS N N OKLAHOMA N B N TEXAS N B S TEXAS A B W TEXAS N B MINNESOTA B A IOWA B N MISSOURI N N ARKANSAS N N LOUISIANA N N WISCONSIN B A ILLINOIS B N MISSISSIPPI N N MICHIGAN B A INDIANA B A OHIO B A KENTUCKY B N TENNESSEE B N ALABAMA N N NEW YORK B A VERMONT B A NEW HAMP B A MAINE B A MASS B A CONN B A RHODE ISL B A PENN B A NEW JERSEY B A W VIRGINIA B N MARYLAND B N DELAWARE B N VIRGINIA B N N CAROLINA N N S CAROLINA N N GEORGIA N N FL PNHDL N N FL PENIN N N AK N SLOPE B A AK ALEUTIAN N A AK WESTERN B A AK INT BSN B A AK S INT B A AK S COAST B A AK PNHDL B 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