PROGNOSTIC DISCUSSIONS FOR 6 TO 10 AND 8 TO 14 DAY OUTLOOKS NWS CLIMATE PREDICTION CENTER CAMP SPRINGS MD 300 PM EDT FRI MAY 2 2003 SEE 6-10 DAY SERVICE CHANGE PROPOSAL AT /LOWER CASE/ HTTP://WWW.CPC.NCEP.NOAA.GOV/PRODUCTS/PREDICTIONS/610DAY/ SERVICE_CHANGE.HTML 6 TO 10 DAY OUTLOOK FOR MAY 8 - 12 2003 . . . . . . . TODAY THERE IS MUCH BETTER AGREEMENT AMONG THE VARIOUS MODELS ON THE 6 TO 10 DAY MEAN 500-HPA CIRCULATION PATTERN AFFECTING NORTH AMERICA ... BUT THERE IS NOT VERY GOOD CONTINUITY OR CONSISTENCY WITH MANY OF THE SOLUTIONS SEEN YESTERDAY. NONE OF THE MODELS ARE BUILDING A STRONG RIDGE NEAR THE WEST COAST AS THE ECMWF DID YESTERDAY... BUT THE ECMWF IS BUILDING A STRONG ZONALLY ORIENTED MID-LATITUDE RIDGE FARTHER TO THE WEST OVER THE CENTRAL PACIFIC. IN SPITE OF THE GOOD AGREEMENT OVER NORTH AMERICA... THERE ARE CONSIDERABLE DIFFERENCES OVER THE PACIFIC... MAINLY ON THE LOCATION AND STRENGTH OF INDICATED MID-LATITUDE RIDGING AND HOW STRONG A TROUGH WOULD BE LEFT NEAR THE U.S. WEST COAST. MODEL OF THE DAY: ENSEMBLE MEAN FORECAST CONFIDENCE FOR THE 6 TO 10 DAY PERIOD IS RATED AS AVERAGE TODAY... 3 ON A SCALE FROM 1 TO 5...DUE PRIMARILY TO GOOD MODEL AGREEMENT TODAY OVER THE U.S. BALANCED BY POOR CONSISTENCY AND CONTINUITY FROM MANY OF YESTERDAYS SOLUTIONS. THE OFFICIAL HEIGHT PROG FOR TODAY IS BASED ON 30 PERCENT OF TODAYS ECMWF CENTERED ON DAY 7... 40 PERCENT OF TODAYS 0Z GFS ENSEMBLE MEAN CENTERED ON DAY 8... AND 20 PERCENT OF TODAYS OPERATIONAL 0Z GFS CENTERED ON DAY 8... AND 10 PERCENT OF TODAYS DAVA CENTERED ON DAY 8. THE TEMPERATURE PROG IS BASED MAINLY ON THE KLEIN AND NEURAL NET SPECIFICATIONS FROM THE OFFICIAL 500-HPA BLEND FIELD... WHICH WERE IN BETTER AGREEMENT AND HAD BETTER DEFINED PATTERNS THAN EARLIER IN THE WEEK. MEAN 850-HPA GFS TEMPERATURE ERRORS FOR THE PAST WEEK AND MONTH... AS WELL AS ANALOGS TO THE MODELS WERE ALSO CONSIDERED. THE ANALOGS WERE IN QUITE GOOD AGREEMENT TODAY WITH THE IMPROVED MODEL AGREEMENT. THE MOS MODEL OUTPUT WAS ALSO IN GOOD AGREEMENT. THE PRECIPITATION PROG IS BASED ON THE NEURAL NET SPECIFICATIONS FROM THE OFFICIAL 500-HPA HEIGHT PROG... THE CALIBRATED AND BIAS-CORRECTED PRECIPITATION FORECASTS FROM THE OPERATIONAL 00Z GFS RUN... AND ANA- LOGS FROM THE VARIOUS MODELS. THERE IS MUCH BETTER AGREEMENT AMONG THE ANALOG PATTERNS TO THE VARIOUS MODELS TODAY THAN YESTERDAY. . . . . . . . 8 TO 14 DAY OUTLOOK FOR MAY 10 - 16 2003 MOST MODELS HAD FAIRLY GOOD AGREEMENT ON THE GENERAL CHARACTER OF THE 8 TO 14 DAY MEAN CIRCULATION PATTERN... EXCEPT FOR THE DAVA AND THE 12Z GFS... THE LATTER OF WHICH STILL HAD A TROUGH JUST OFF THE EAST COAST. THERE IS AN INCREASING TREND TOWARDS A MORE ZONAL FLOW IN ALL SECTORS EXCEPT THE ASIAN... WHERE THE BLOCK INITIALLY OVER ALASKA IS PREDICTED TO RETROGRADE TO BY THE 8-14 DAY PERIOD. THE MAIN DIF- FERENCES IN THE MODELS OF INTEREST TO THE U.S. FORECAST IS HOW MUCH TROUGH MAY COME INLAND IN THE MEAN AND HOW FAR EAST IT WILL BE BY THE WEEK TWO PERIOD. THE 00Z AND 06Z GFS RUNS HAVE IT FARTHEST INLAND AND STRONGEST... AND SINCE THEY ARE THE LATEST GFS RUNS AVAILABLE AT THE TIME THE BLEND WAS MADE.. AND THE ECWMF SOLUTION FOR THE 6-10 DAY PERIOD WAS ALREADY HINTING AT SHORT WAVE ENERGY COMING INLAND IN FAST WESTERLY FLOW... THE FASTER SOLUTIONS WERE FAVORED. FASTER PROGRESS- ION IS ALSO CONSISTENT WITH THE TREND TOWARDS A MORE ZONAL PATTERN DEPICTED BY NEARLY ALL OF THE MODELS. CONFIDENCE IN THE WEEK 2 FORECAST IS AVERAGE FOR THIS TIME FRAME... 3 ON A SCALE FROM 1 TO 5... DUE TO IMPROVED MODEL AGREEMENT TODAY. THE OFFICIAL 500-HPA HEIGHT BLEND FOR THE 8 TO 14 DAY PERIOD CONSISTS OF 30 PERCENT OF TODAYS ENSEMBLE MEAN CENTERED ON DAY 11... 45 PER- CENT OF THE OPERATIONAL 00Z GFS FOR THE 8 TO 14 DAY PERIOD... AND 25 PERCENT OF THE ECMWF 5-DAY MEAN CENTERED ON DAY 7. THE TEMPERATURE PROG IS BASED ON THE KLEIN AND NEURAL NET SPECIFICA- TIONS FROM THE OFFICIAL 500-HPA HEIGHT PROG... WITH CONSIDERATION OF THE ANALOGS TO THE VARIOUS MODELS. THE PRECIPITATION PROG IS BASED ON NEURAL NET SPECIFICATIONS FROM THE OFFICIAL 500-HPA HEIGHT PROG... BIAS-CORRECTED AND CALIBRATED RAINFALL FROM THE 00Z OPERATIONAL GFS MODEL... AND ANALOGS FROM THE VARIOUS 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:--------------------------------------------- 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 MAY 15 2003. 6 to 10 day Outlook Table STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN WASHINGTON B A OREGON B N NRN CALIF N B SRN CALIF N B IDAHO B B NEVADA N B W MONTANA B N E MONTANA B N WYOMING N B UTAH N B ARIZONA A B COLORADO N N NEW MEXICO N N N DAKOTA N N S DAKOTA N N NEBRASKA N N KANSAS N A OKLAHOMA N A N TEXAS A A S TEXAS A A W TEXAS N A MINNESOTA N N IOWA N N MISSOURI A A ARKANSAS A A LOUISIANA A A WISCONSIN N N ILLINOIS A A MISSISSIPPI A A MICHIGAN A A INDIANA A A OHIO A A KENTUCKY A A TENNESSEE A A ALABAMA A A 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 A NEW JERSEY A N W VIRGINIA A A MARYLAND A N DELAWARE A N VIRGINIA A A N CAROLINA A A S CAROLINA A A GEORGIA A A FL PNHDL A N FL PENIN A N AK N SLOPE B B AK ALEUTIAN A A AK WESTERN A N AK INT BSN B B AK S INT N N AK SO COAST N N AK PNHDL N N 8 to 14 day Outlook Table STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN WASHINGTON N N OREGON N B NRN CALIF N B SRN CALIF A B IDAHO N B NEVADA A B W MONTANA N B E MONTANA N B WYOMING A B UTAH A B ARIZONA A B COLORADO A B NEW MEXICO A N N DAKOTA N B S DAKOTA N N NEBRASKA N N KANSAS N A OKLAHOMA N A N TEXAS N N S TEXAS N N W TEXAS N A MINNESOTA N N IOWA N N MISSOURI N N ARKANSAS A N LOUISIANA A N WISCONSIN N N ILLINOIS A N MISSISSIPPI A N MICHIGAN N N INDIANA A N OHIO A N KENTUCKY A N TENNESSEE A N ALABAMA A N NEW YORK A B VERMONT N B NEW HAMP N B MAINE N N MASS N B CONN N B RHODE IS N B PENN A B NEW JERSEY A B W VIRGINIA A N MARYLAND A B DELAWARE A B VIRGINIA A N N CAROLINA A A S CAROLINA A A GEORGIA A A FL PNHDL A A FL PENIN A N AK N SLOPE B B AK ALEUTIAN N A AK WESTERN B N AK INT BSN B B AK S INT N N AK SO COAST N A AK PNHDL N A 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. $$