PROGNOSTIC DISCUSSIONS FOR 6 TO 10 AND 8 TO 14 DAY OUTLOOKS NWS CLIMATE PREDICTION CENTER CAMP SPRINGS MD 300 PM EST THURS APR 3 2003 6 TO 10 DAY OUTLOOK FOR APR 9 - 13 2003 . . . . . . . THE MAIN MODELS ARE IN REASONABLE AGREEMENT THROUGH DAY 3 TODAY...BUT DIFFERENCES IN TIMING AND INTENSITY OF THE SHORT WAVES BECOME APPARENT BY DAY 4. BUT AGAIN TODAY ALL THE MAIN MODELS FORECAST AN ACTIVE BUT PROGRESSIVE PATTERN OF MODERATE TO LARGE AMPLITUDE SHORT WAVES OVER NORTH AMERICA AND NEARBY OCEANIC REGIONS...WITH THE 0Z GFS AND THE ECMWF DEFINING THE EXTREMES OF SHORT WAVE DIFFERENCES. BY DAY 6 THE GFS IS MORE PROGRESSIVE AND A BIT MORE AMPLIFIED IN THE SOUTHERN STREAM THAN THE ECMWF...BUT THE MRF AND ECMWF ENSEMBLE MEANS ARE CLOSER IN THE SOUTHERN STREAM. THE DIFFERENCES IN THE OPERATIONAL 0Z GFS AND ECMWF CONTINUE INTO THE MEAN PATTERNS PREDICTED FOR THE 6 TO 10 DAY PERIOD...WITH THE ECMWF HAVING A MUCH MORE AMPLIFIED PATTERN OVER NORTH AMERICA THAN ANY OF THE GFS-BASED 500-HPA MEAN FIELDS. AGAIN TODAY THE GFS RUNS APPEAR TO BE PLAYING CATCH-UP WITH THE ECMWF IN THIS REGARD AS TODAYS GFS RUNS ARE MORE AMPLIFIED THAN YESTERDAYS. THE ECMWF HAS A PRONOUNCED SPLIT FLOW...WITH A STRONG RIDGE DOMINATING THE WESTERN HALF OF THE CONTINENT AND A POSITIVELY TILTED MEAN TROUGH FROM NORTHERN MEXICO TO THE GREAT LAKES. THE GFS ENSEMBLE MEAN...18Z GFS...AND THE DAVA HAVE BASICALLY ZONAL FLOW WITH LOW AMPLITUDE WAVES IN THE MEAN FIELD OVER NORTH AMERICA...WITH SOME HINT OF SPLIT FLOW. THE 0Z...6Z...AND TO SOME EXTENT YESTERDAYS 12Z GFS FIELDS HAVE HIGHER AMPLITUDE THAN THE OTHER GFS SOLUTIONS BUT HAVE A MORE NEUTRALLY TILTED MEAN TROUGH OVER THE EASTERN U.S. IN THE VICINITY OF ALASKA ABOUT HALF THE MODELS HAVE STRONG SOUTHERLY TO SOUTHWESTERLY 500-HPA FLOW INTO THE SOUTH COAST AND ESPECIALLY THE PANHANDLE WHILE OTHERS HAVE A CLOSED LOW OVER THE GULF OF ALASKA BUT NO STRONG FLOW INTO THE COAST. ENSEMBLE MEMBERS SHOW A TYPICAL AMOUNT OF SPREAD DURING THE 6 TO 10 DAY PERIOD. THE MRF AND ECMWF ENSEMBLE MEANS ARE PHASED SIMILARLY THROUGH ABOUT DAY 8...WITH THE MRF ENSEMBLE MEAN HAVING HIGHER AMPLITUDE AGAIN TODAY. BY DAY 10 THE MEANS HAVE SHIFTED TO BEING OUT OF PHASE THOUGH...BUT BY THEN THE SPREAD IS LARGE ENOUGH THAT ALMOST ANY PHASE IS REPRESENTED BY SOME ENSEMBLE MEMBER. THE OFFICIAL 500-HPA HEIGHT FORECAST FOR THE 6 TO 10 DAY PERIOD USES 30 PERCENT OF THE ECMWF MODEL CENTERED ON DAY 7...40 PERCENT OF THE GFS ENSEMBLE MEAN CENTERED ON DAY 8...AND 30 PERCENT OF THE 0Z OPERATIONAL GFS CENTERED ON DAY 8. MODEL OF THE DAY: GFS ENSEMBLE MEAN FORECAST CONFIDENCE IS RATED AS ABOUT AVERAGE TODAY...3 ON A SCALE FROM 1 TO 5. THE TEMPERATURE PROG IS BASED ON THE KLEIN AND NEURAL NET SPECIFICATIONS FROM THE 500-HPA BLEND FIELD AND THE MOS FORECAST BASED ON THE ENSEMBLE MEMBERS. THE PRECIPITATION PROG IS BASED ON THE NEURAL NET SPECIFICATIONS FROM THE OFFICIAL 500-HPA HEIGHT PROG...THE CALIBRATED PRECIPITATION FORECAST FROM THE OPERATIONAL 0Z GFS RUN...AND FROM ANALOGS TO THE GFS ENSEMBLE MEAN...0Z GFS...AND ECMWF 500-HPA HEIGHT PROGS. . . . . . . . 8 TO 14 DAY OUTLOOK FOR APR 11 - 17 2003 FOR THE WEEK 2 PERIOD THE OVERALL FLOW PATTERNS PREDICTED BY THE GFS- BASED SOLUTIONS ARE IN UNUSUALLY GOOD AGREEMENT...EXCEPT FOR THE DAVA WHICH AS OFTEN HAPPENS HAS A RELATIVE LACK OF STRONG FEATURES. THE GFS MODEL SOLUTIONS ALL HAVE A STRONG POSITIVE ANOMALY FORECAST IN THE VICINITY OF THE GREAT LAKES AND A NEGATIVE ANOMALY IN THE VICINITY OF THE WEST COAST. CONFIDENCE IN THE WEEK 2 FORECAST IS ABOUT AVERAGE...3 ON A SCALE FROM 1 TO 5. THE OFFICIAL 500-HPA HEIGHT FORECAST FOR THE 8 TO 14 DAY PERIOD USES 50 PERCENT OF THE GFS ENSEMBLE MEAN CENTERED ON DAY 11...25 PERCENT OF THE 0Z GFS CENTERED ON DAY 11...AND 25 PERCENT OF THE GFS ENSEMBLE MEAN CENTERED ON DAY 7. THE TEMPERATURE PROG IS BASED ON THE NEURAL NETWORK AND KLEIN SPECIFICATIONS FROM THE OFFICIAL D+11 HEIGHT PROG. THE PRECIPITATION PROG IS BASED ON NEURAL NET FORECASTS FROM THE OFFICIAL 500-HPA HEIGHT PROG...CALIBRATED PRECIPITATION FROM THE 0Z RUN OF THE GFS MODEL...AND FROM ANALOGS TO THE ENSEMBLE MEAN 500-HPA FIELD. FORECASTER: R. MARTIN . . . . . . . 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:--------------------------------------------- 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. ANALOG (NATURAL ANALOG) - A WEATHER MAP THAT RESEMBLES ANOTHER WEATHER MAP - USUALLY FROM DIFFERENT YEARS BUT THE SAME SEASON IN THE HISTORICAL RECORD. THE CRITERION FOR SELECTING AN ANALOG IS OFTEN THE PATTERN CORRELATION BETWEEN THE MAPS. TWO MAPS WILL JUST BEGIN TO RESEMBLE EACH OTHER TO THE HUMAN EYE AT A PATTERN CORRELATION OF ABOUT 40%. TO BE USEFUL - ANALOGS NEED TO HAVE MUCH HIGHER CORRELATIONS TO THE ORIGINAL MAP THAN THAT - 80% OR MORE. ANALOGS ARE INCREASINGLY DIFFICULT TO FIND AS THE GEOGRAPHIC REGION BEING STUDIED INCREASES IN SIZE. PERFECT ANALOGS TO THE ENTIRE NORTHERN HEMISPHERE SIMPLY DO NO EXIST - FOR PRACTICAL PURPOSES. THIS IS WHY SIMPLE NATURAL ANALOG FORECAST METHODS DO NOT WORK VERY WELL. 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. AO - ARCTIC OSCILLATION - A MEASURE OF THE DIFFERENCE BETWEEN THE MEAN MID-TROPOSPHERIC HEIGHT OR SEA LEVEL PRESSURE ANOMALY OVER THE POLAR BASIN AND THE CORRESPONDING AVERAGE ANOMALY IN A RING SURROUNDING THE POLAR BASIN AT MIDDLE LATITUDES. THE AO IS CONSIDERED TO BE THE LEADING MODE OF CLIMATE VARIABILITY OF THE EXTRATROPICAL NORTHERN HEMISPHERE. THE AO CAN ALSO BE CONSIDERED TO INCLUDE THE NAO (NORTH ATLANTIC OSCILLATION) WITH WHICH IT IS POSITIVELY CORRELATED - BUT NOT IDENTICAL. THE PHASE OF THE AO IS CONSIDERED TO BE POSITIVE WHEN HEIGHTS OR PRESSURES ARE BELOW NORMAL OVER THE ARCTIC BASIN AND ABOVE NORMAL OVER SURROUNDING MID- LATITUDES - AND IS NEGATIVE FOR THE REVERSE ANOMALY PATTERN. 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 - CONTERMINOUS 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. 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. GFS - GLOBAL FORECAST SYSTEM. THIS REFERS TO ANY OF THE GLOBAL MODELS RUN AT NCEP FOUR TIMES A DAY THAT USED TO BE REFERRED TO AS THE MRF AND AVN MODELS. THE MODEL RUN INITIATED AT 00Z (00 GMT) IS CURRENTLY THE ONLY ONE USED BY CPC IN ITS OFFICIAL BLEND FORECAST - ALTHOUGH THE OTHERS CAN BE CONSIDERED BY THE FORECASTER IN FORMULATING THE TEMPERATURE AND PRECIPITATION FORECASTS. GFS ENSEMBLE - A SET OF GFS FORECASTS WHICH ARE ALL VALID AT THE SAME TIME BUT WHOSE STARTING CONDITIONS DIFFER BY SMALL AMOUNTS. THERE ARE CURRENTLY 25 MEMBERS IN THE GFS ENSEMBLE. THE AVERAGE OF THESE IS THE GFS ENSEMBLE MEAN. 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 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 SURFACE 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. MJO - MADDEN-JULIAN OSCILLATION - ALSO CALLED TROPICAL INTRA-SEASONAL OSCILLATION - A SERIES OF WAVES WITH A PERIOD AVERAGING 50 DAYS THAT MOVES SLOWLY EASTWARD NEAR THE EQUATOR ALTERNATELY ENHANCING AND SUPRESSING PRECIPITATION. NAO - NORTH ATLANTIC OSCILLATION TELECONNECTION PATTERN. IT CAN ALSO BE VIEWED AS THE ATLANTIC HALF OF THE AO (ARCTIC OSCILLATION) TELECONNECTION PATTERN - STRONGLY INFLUENCES TEMPERATURES OVER EUROPE AND MUCH OF NORTH AMERICA - ESPECIALLY DURING THE COLD SEASONS - AND DETERMINES THE MEAN LATITUDE OF THE PREVAILING STORM TRACKS ACROSS THE NORTH ATLANTIC. THE PHASE OF THE NAO IS CONSIDERED POSITIVE WHEN PRESSURES AND HEIGHTS ARE BELOW NORMAL OVER GREENLAND AND ICELAND (STRONG ICELANDIC LOW) AND ABOVE NORMAL AT MIDDLE AND SUBTROPICAL LATITUDES (STRONG BERMUDA-AZORES HIGH) - AND NEGATIVE FOR THE REVERSE ANOMALIES. PNA - PACIFIC NORTH AMERICAN TELECONNECTION PATTERN. PROG - PROGNOSIS - OR FORECAST. PROGRESSION OR PROGRESSIVE MOTION - THE NORMAL MOVEMENT OF ATMOSPHERIC WEATHER SYSTEMS (HIGHS... LOWS... RIDGES... OR TROUGHS) FROM WEST TO EAST IN THE MIDDLE LATITUDES. RETROGRESSION OR RETROGRADE MOTION - A TYPE OF MOTION SOMETIMES OBSERVED IN WEATHER SYSTEMS WHEN THEY END UP IN POSITIONS FURTHER TO THE WEST THAN THEIR ORIGINAL LOCATIONS - CONTRARY TO THEIR USUAL WEST TO EAST MOTION. 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 THURSDAY APRIL 17 2003. 6 to 10 day Outlook Table STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN WASHINGTON A N OREGON A N NRN CALIF N N SRN CALIF N A IDAHO A B NEVADA A N W MONTANA A B E MONTANA A B WYOMING A B UTAH A B ARIZONA A N COLORADO A B NEW MEXICO N N N DAKOTA A B S DAKOTA A B NEBRASKA A B KANSAS A B OKLAHOMA A B N TEXAS A N S TEXAS N N W TEXAS N N MINNESOTA A B IOWA A B MISSOURI A B ARKANSAS A B LOUISIANA N N WISCONSIN A B ILLINOIS A B MISSISSIPPI N A MICHIGAN A B INDIANA A B OHIO A N KENTUCKY A B TENNESSEE N N ALABAMA N A NEW YORK A N VERMONT A N NEW HAMP A N MAINE N N MASS A N CONN A N RHODE IS A N PENN A N NEW JERSEY A A W VIRGINIA A N MARYLAND A A DELAWARE A A VIRGINIA A A N CAROLINA A A S CAROLINA N A GEORGIA N A FL PNHDL N A FL PENIN N A AK N SLOPE A B AK ALEUTIAN N N AK WESTERN N A AK INT BSN N N AK S INT N N AK SO COAST N A AK PNHDL N N 8 to 14 day Outlook Table STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN WASHINGTON N N OREGON N N NRN CALIF B A SRN CALIF B A IDAHO N N NEVADA N A W MONTANA N N E MONTANA N N WYOMING N N UTAH N N ARIZONA N A COLORADO N A NEW MEXICO N A N DAKOTA A N S DAKOTA A N NEBRASKA A N KANSAS A A OKLAHOMA A A N TEXAS A A S TEXAS A A W TEXAS N A MINNESOTA A B IOWA A B MISSOURI A N ARKANSAS A N LOUISIANA A N WISCONSIN A B ILLINOIS A N MISSISSIPPI A N MICHIGAN A B INDIANA A N OHIO A N KENTUCKY A N TENNESSEE A N ALABAMA A N NEW YORK A N VERMONT A N NEW HAMP A N MAINE A N MASS A N CONN A N RHODE IS A N PENN A N NEW JERSEY A N W VIRGINIA A N MARYLAND A N DELAWARE A N VIRGINIA A N N CAROLINA A N S CAROLINA A N GEORGIA A N FL PNHDL A A FL PENIN A N AK N SLOPE N N AK ALEUTIAN N N AK WESTERN N A AK INT BSN N N AK S INT N N AK SO 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 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 KWBC - ON AWIPS AS PMDMRD. $$