PROGNOSTIC DISCUSSIONS FOR 6 TO 10 AND 8 TO 14 DAY OUTLOOKS NWS CLIMATE PREDICTION CENTER CAMP SPRINGS MD 300 PM EDT MON MAY 19 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 25 - 29 2003 . . . . . . . THE CIRCULATION MODELS FOR THE UPCOMING 6-10 DAY PERIOD ARE ONLY IN FAIR AGREEMENT TODAY OVER THE NORTH AMERICAN SECTOR...WITH THE MOST SIGNIFICANT DIFFERENCES BEING LOCATED OVER THE EASTERN HALF OF THE LOWER 48. TODAYS 0Z GFS ENSEMBLE MEAN ... AND THE 0Z AND 6Z GFS MODELS...ARE SIMILAR IN THEIR DEPICTION OF A MODERATELY INTENSE TROUGH OVER THE EASTERN U.S...AND A LARGE AREA OF RIDGING FLANKING THIS TROUGH TO THE WEST AND TO THE NORTH. THE PRIMARY DIFFERENCES ARE THAT THE 0Z AND 6Z GFS RUNS ARE MORE INTENSE ON THESE FEATURES THAN IS THE ENSEMBLE MEAN...WITH THE 0Z GFS ALSO BEING QUITE A BIT SLOWER. A LARGE AREA OF BELOW AVERAGE 500 HPA HEIGHTS EXTENDS FROM ALASKA SOUTHWARD ACROSS THE GULF OF ALASKA...WITH A GENERAL CONSEN- SUS OF A NEGATIVE CENTER POSITIONED SOMEWHERE NEAR 42N/150W. THE ECMWF AND DAVA D+8 SOLUTIONS ARE PREDICTING MUCH LESS OF A TROUGH ACROSS THE EAST...WITH THE ECMWF BEING THE MOST BULLISH ON RIDGING SPREADING INTO THAT AREA. WITH THESE TWO MODELS...THE WEAK NEGATIVE ANOMALY CENTER ASSOCIATED WITH THE EASTERN TROUGH IS MUCH FURTHER SOUTH...EITHER OVER THE GULF COAST STATES OR OUT OVER THE OPEN GULF. THE NCEP SPAGHETTI MAPS STRONGLY FAVOR A TROUGH OVER THE EAST...AND THE LATEST GFS MODEL BIASES SHOW THAT THE GFS HAS UNDERESTIMATED THE TROUGHING AND COOL WEATHER ACROSS THE NORTHEAST. IT DOES LOOK AS IF THE NORTH AMERICAN WAVETRAIN MAY BE LOCKING IN AND AMPLIFYING DURING THIS TIME. MODEL OF THE DAY: GFS ENSEMBLE MEAN FORECAST CONFIDENCE FOR THE 6 TO 10 DAY PERIOD IS RATED NEAR AVE- RAGE TODAY...3 ON A SCALE FROM 1 TO 5. THE OFFICIAL HEIGHT PROG FOR TODAY IS BASED ON 10 PERCENT OF TODAYS ECMWF CENTERED ON DAY 7...40 PERCENT OF TODAYS 0Z GFS ENSEMBLE MEAN CENTERED ON DAY 8...30 PERCENT OF TODAYS 0Z OPERATIONAL GFS RUN CENTERED ON DAY 8 AND 20 PERCENT OF TODAYS DAVA RUN CENTERED ON DAY 8. THE TEMPERATURE PROG IS BASED ON THE KLEIN SPECIFICATIONS FROM THE OFFICIAL 500-HPA HEIGHT PROG...THE 0Z GFS BIAS-CORRECTED 850-HPA TEMPERATURES...AND MOS TEMPERATURE SPECIFICATIONS FROM THE ENSEMBLE MEMBERS. THE PRECIPITATION PROG IS BASED ON THE NEURAL NET SPECIFICATIONS FROM THE OFFICIAL 500-HPA HEIGHT PROG...ACCUMULATED - AND BIAS CORRECTED PRECIPITATION FROM THE GFS RUNS. . . . . . . . 8 TO 14 DAY OUTLOOK FOR MAY 27 - JUN 2 2003 DURING THE WEEK 2 PERIOD...THE OVERALL CIRCULATION PATTERN IS FORE- CAST TO CHANGE LITTLE...THOUGH SOME DEAMPLIFICATION IS POSSIBLE. THERE ARE TIMING DIFFERENCES REGARDING THE PERSISTENT AND RELOADED EASTERN TROUGH...WITH THE 6Z GFS BEING THE MOST PROGRESSIVE...THE 0Z GFS BEING THE SLOWEST AND MOST INTENSE...AND THE ENSEMBLE MEAN SOME- WHERE INBETWEEN. THE DAVA HAS ABOVE AVERAGE HEIGHTS ACROSS ALL BUT THE SOUTHEASTERN QUARTER OF THE LOWER 48. CONFIDENCE IN THE WEEK 2 FORECAST IS NEAR AVERAGE FOR THIS TIME RANGE ...3 ON A SCALE FROM 1 TO 5. THE OFFICIAL 500-HPA HEIGHT BLEND FOR THE 8 TO 14 DAY PERIOD CONSISTS OF 70 PERCENT OF TODAYS GFS ENSEMBLE MEAN CENTERED ON DAY 11... 10 PERCENT OF TODAYS 0Z OPERATIONAL GFS RUN CENTERED ON DAY 11... AND 20 PERCENT OF TODAYS DAVA CENTERED ON DAY 11. THE TEMPERATURE PROG IS BASED ON THE KLEIN AND NEURAL NET SPECIFICA- TIONS FROM THE OFFICIAL 500-HPA HEIGHT PROG...AND ON THE 0Z GFS BIAS- CORRECTED 850-HPA TEMPERATURES. THE PRECIPITATION PROG IS BASED ON NEURAL NET SPECIFICATIONS FROM THE OFFICIAL 500-HPA HEIGHT PROG...AND ACCUMULATED AND BIAS CORRECT- ED PRECIPITATION FROM THE GFS RUNS. 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:--------------------------------------------- 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 JUN 19 2003. 6 to 10 day Outlook Table STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN WASHINGTON A N OREGON A B NRN CALIF A B SRN CALIF A B IDAHO A B NEVADA A B W MONTANA A B E MONTANA A B WYOMING A B UTAH A B ARIZONA A B COLORADO A N NEW MEXICO A A N DAKOTA A B S DAKOTA A B NEBRASKA A B KANSAS N N OKLAHOMA B A N TEXAS B N S TEXAS B N W TEXAS N N MINNESOTA A B IOWA N N MISSOURI B N ARKANSAS B A LOUISIANA B N WISCONSIN A N ILLINOIS B N MISSISSIPPI B N MICHIGAN N A INDIANA B A OHIO B A KENTUCKY B A TENNESSEE B A ALABAMA B N NEW YORK N A VERMONT N A NEW HAMP N A MAINE A N MASS N A CONN B A RHODE IS B A PENN B A NEW JERSEY B A W VIRGINIA B A MARYLAND B A DELAWARE B A VIRGINIA B A N CAROLINA B A S CAROLINA B N GEORGIA B N FL PNHDL B N FL PENIN B N AK N SLOPE B N AK ALEUTIAN N B AK WESTERN B B AK INT BSN N N AK S INT A B AK SO COAST A B AK PNHDL N A 8 to 14 day Outlook Table STATE TEMP PCPN STATE TEMP PCPN STATE TEMP PCPN WASHINGTON A N OREGON A B NRN CALIF A B SRN CALIF A B IDAHO A B NEVADA A B W MONTANA A N E MONTANA A N WYOMING A B UTAH A B ARIZONA A B COLORADO A B NEW MEXICO A B N DAKOTA A N S DAKOTA A N NEBRASKA N N KANSAS N N OKLAHOMA N N N TEXAS N N S TEXAS N N W TEXAS N B MINNESOTA N N IOWA N N MISSOURI N N ARKANSAS B N LOUISIANA B A WISCONSIN N N ILLINOIS N N MISSISSIPPI B A MICHIGAN N A INDIANA N N OHIO N A KENTUCKY B A TENNESSEE B A ALABAMA B A NEW YORK N A VERMONT N A NEW HAMP N A MAINE N N MASS B A CONN B A RHODE IS B A PENN N A NEW JERSEY B A W VIRGINIA B A MARYLAND B A DELAWARE B A VIRGINIA B A N CAROLINA B A S CAROLINA B A GEORGIA B A FL PNHDL B A FL PENIN B A AK N SLOPE B B AK ALEUTIAN N B AK WESTERN B B AK INT BSN N B AK S INT A N AK SO COAST A N AK PNHDL A B 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. $$