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 25 2002 6 TO 10 DAY OUTLOOK FOR JAN 31 - FEB 04 2002 . . . . . . . . MODEL COMPARISONS: MRF... MRF ENSEMBLE MEAN... ECMWF AND DAVA ARE NOT IN QUITE AS MUCH DISAGREEMENT AS YESTERDAY... BUT WE STILL HAVE TO DISPOSE OF AN ARCTIC OUTBREAK THAT NOW OCCURS MAINLY IN THE 3-5 DAY PERIOD. MOST OF THE CORE OF THE ARCTIC AIR SEEMS TO BE SHUNTED RAPIDLY EAST... FOLLOWED BY MORE COLD AIR BUT NOT THE COLD CORE OF THE ARCTIC AIR. THE MRF AND MRF-BASED ENSEMBLE MEAN ARE IN FAIRLY GOOD AGREEMENT TODAY. THEY RESEMBLE YESTERDAYS MRF WEEKLY MEAN PROG FOR THE WEEK TWO PERIOD... WHICH IS A STRONG INDICATION THAT THE ATMOSPHERE IS UNDERGOING A RAPID CHANGE OF PATTERN THAT THE MODELS ARE CONSIDERABLY TOO SLOW IN PREDICTING. THE ECMWF SOLUTION HAS A HUGE AMPLIFIED TROUGH-RIDGE-TROUGH PATTERN ACROSS THE PACIFIC... WITH THE DOWNSTREAM TROUGH JUST OFF THE U.S. WEST COAST. OVER THE REST OF NORTH AMERICA AND THE ATLANTIC VERY FAST ZONAL FLOW PREVAILS AT MIDDLE LATITUDES. THE DAVA PROG WAS ROUGHLY SIMILAR IN PHASE TO THE ECMWF... BUT LESS AMPLIFIED. AGAIN TODAY THE TEMPERATURE SPECIFICATIONS ON THE MRF DO NOT LOOK AS COLD AS THE MRF DAILY MAPS DO... PERHAPS BECAUSE THE KLEINS DO NOT HANDLE SHALLOW ARCTIC AIR VERY WELL (NOT COLD ENOUGH) AND THE NEURAL NET IS AWARE THAT HEIGHTS ARE FALLING RAPIDLY OVER ALASKA AND THE NORTH PACIFIC... REDUCING THE UPSTREAM POTENTIAL SOURCE AND STEERING FOR ARCTIC AIR. THE MOS TEMPERATURES AND COMPOSITE ANALOGS WERE SOMEWHAT COLDER LOOKING. THE ANOMALY CORRELATION SCORES BETWEEN THE MODEL SOLUTIONS FOR THE 6-10 DAY PERIOD AND THE BEST ANALOG COMPOSITES WERE RATHER LOW... FROM THE 70S TO THE MID 80S AT BEST... AGAIN WARNING OF CONSIDERABLE UNCERTAINTY AND THE LIKELIHOOD THAT THE PREDICTED PATTERNS ARE PROBABLY TRANSITIONAL. . . . . . . . . CONFIDENCE IN TODAYS FORECAST REMAINS DOWNGRADED TO BELOW AVERAGE... 2 ON A 1-5 SCALE... DUE MAINLY TO UNCERTAINTY IN TIMING OF PATTERN CHANGES. THE OFFICIAL 500 HPA HEIGHT FORECAST FOR THE 6 TO 10 DAY PERIOD USES 60 PERCENT OF TODAYS MRF ENSEMBLE MEAN CENTERED ON DAY 8... 15 PERCENT OF TODAYS OPERATIONAL MRF CENTERED ON DAY 8... 10 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 AND THE NEURAL NET TEMPERATURE SPECIFICATIONS FROM THE 500 HPA BLEND... COMPOSITES OF THE PAST OBSERVED BEST ANALOGS TO THE BLEND... AND THE MODEL OUTPUT STATISTICAL (MOS) TEMPERATURE SPECIFICATION BASED ON THE MRF. 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 BEST PAST OBSERVED ANALOGS TO THE HEIGHT FORECAST. 8 TO 14 DAY OUTLOOK FOR FEB 02 - 08 2002 MODEL COMPARISONS: MRF... MRF ENSEMBLE AND DAVA FORECASTS ARE STILL RATHER DIVERGENT BUT IN BETTER AGREEMENT THAN THEY WERE YESTERDAY... WITH DAVA SIMILAR TO ITS 6-10 DAY VERSION WHILE THE MRF AND MRF ENSEMBLE MEANS LOOKED LIKE REASONABLE PROGRESSIONS FROM THEIR 6-10 DAY PATTERNS. THE WEEK TWO PATTERN IS BASICALLY ONE WITH BELOW NORMAL HEIGHTS AT HIGH LATITUDES AND STRONG ZONALLY ORIENTED RIDGES AT MIDDLE LATITUDES AROUND THE HEMISPHERE - A PATTERN THAT GIVES PREDOMINANTLY MILD WEATHER AT MIDDLE LATITUDES IN THE WINTER. . . . . . . . . CONFIDENCE IN TODAYS FORECAST REMAINS SOMEWHAT UNCERTAIN... RATED 2 ON A SCALE OF 1-5... DUE TO SOMEWHAT DIFFERING SOLUTIONS AND ATTENDANT UNCERTAINTIES OF ADJUSTMENTS OF THE SURFACE WEATHER TO A RAPIDLY CHANGING CIRCULATION PATTERN. 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... 20 PERCENT OF TODAYS OPERATIONAL MRF CENTERED ON DAY 11... 10 PERCENT OF TODAYS DAVA CENTERED ON DAY 11... 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... MODIFIED SLIGHTLY FOR CORRECTION OF RECENT BIASES IN THE MRF 850 HPA TEMPERATURE PROGS. THE PRECIPITATION FORECAST IS BASED PRIMARILY ON THE BIAS CORRECTED ACCUMULATED MRF OUTPUT... THE NEURAL NET FROM THE 500 HPA BLEND... AND COMPOSITE PATTERNS OF THE PAST BEST ANALOGS TO THE OFFICIAL HEIGHT FORECAST AND MODELS. 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. 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 FEBRUARY 14. 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 B A NEVADA B A W MONTANA B A E MONTANA N A WYOMING B A UTAH B A ARIZONA B A COLORADO B A NEW MEXICO B A N DAKOTA N A S DAKOTA N A NEBRASKA B A KANSAS B A OKLAHOMA B A N TEXAS N A S TEXAS N A W TEXAS B A MINNESOTA N A IOWA N A MISSOURI N A ARKANSAS N A LOUISIANA A N WISCONSIN N A ILLINOIS N A MISSISSIPPI A N MICHIGAN N A INDIANA N A OHIO N A KENTUCKY N A TENNESSEE N A ALABAMA A N NEW YORK N A VERMONT N A NEW HAMP N A MAINE B A MASS N A CONN N A RHODE ISL N A PENN N A NEW JERSEY A A W VIRGINIA N A MARYLAND A A DELAWARE A A VIRGINIA A N N CAROLINA A N S CAROLINA A N GEORGIA A N FL PNHDL A N FL PENIN A N AK N SLOPE B A AK ALEUTIAN N A AK WESTERN B A AK INT BSN N A AK S INT A A AK S COAST A A AK PNHDL B A 8 to 14 day Outlook Table STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN WASHINGTON N N OREGON B N NRN CALIF N N SRN CALIF B B IDAHO B B NEVADA B B W MONTANA N B E MONTANA A B WYOMING A B UTAH B B ARIZONA N B COLORADO N B NEW MEXICO N B N DAKOTA A B S DAKOTA A B NEBRASKA A B KANSAS N B OKLAHOMA N B N TEXAS N N S TEXAS A N W TEXAS N B MINNESOTA A N IOWA A B MISSOURI B N ARKANSAS B N LOUISIANA A A WISCONSIN A B ILLINOIS A B MISSISSIPPI A N MICHIGAN A N INDIANA N B OHIO N N KENTUCKY N N TENNESSEE N N ALABAMA A A NEW YORK N A VERMONT N A NEW HAMP N A MAINE N N MASS N A CONN N A RHODE ISL N A PENN N A NEW JERSEY N A W VIRGINIA A N 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 A B AK ALEUTIAN B N AK WESTERN N A AK INT BSN A B AK S INT A N AK S COAST N A AK PNHDL N 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