000 FXUS10 KWNH 081847 PMDHMD MODEL DIAGNOSTIC DISCUSSION NWS HYDROMETEOROLOGICAL PREDICTION CENTER CAMP SPRINGS MD 146 PM EST SUN NOV 08 2009 VALID NOV 08/1200 UTC THRU NOV 12/0000 UTC ...SEE NOUS42 KWNO ADMNFD FOR THE STATUS OF THE UPPER AIR INGEST... 12Z MODEL EVALUATION INCLUDING THE NEW ECMWF AND FINAL PREFERENCES INITIALIZATION ERRORS WITH THE NAM/GFS DO NOT APPEAR TO SIGNIFICANTLY IMPACTS THEIR FORECASTS. ...LOW PRESSURE AND ASSOCIATED FRONTAL BOUNDARY CURRENTLY OVER THE CENTRAL PLAINS. PREFERENCE: UKMET/ECMWF THE NAM IS A LITTLE DEEPER WITH THE SURFACE LOW ENTERING QUEBEC...OTHERWISE THE MODELS ARE SIMILAR WITH THE ASSOCIATED FRONTAL SYSTEM THROUGH 00Z TUE. MODEL DIFFERENCES BECOME INCREASINGLY APPARENT AFTER 00Z TUE HOWEVER...WITH THE NAM/GFS REMAINING PROGRESSIVE WITH THE FRONT THROUGH THE NORTHEAST/NEW ENGLAND...BUT WITH THE GFS PHASING ITS ASSOCIATED MID/UPPER TROUGH WITH AN UPPER LOW TO ITS SOUTH...RESULTING IN A DEEPENING SURFACE LOW OVER EASTERN NORTH CAROLINA BY 12Z WED. THE 00Z ECMWF IS SLOWEST WITH THE FRONTAL PASSAGE THROUGH NEW ENGLAND DUE IN PART TO GREATER MID LEVEL TROUGH AMPLIFICATION...INCLUDING A SEPARATE SURFACE LOW FORMING NEAR BOSTON BY TUE NGT. WHILE SOME AMPLIFICATION OF A SHORTWAVE TROUGH IN THE LEE OF THE CANADIAN ROCKIES SEEMS REASONABLE EARLY IN THE PERIOD...WHICH IS WHAT ALLOWS THE TROUGH TO AMPLIFY FURTHER OVER THE GREAT LAKES...THE DEGREE AT WHICH THE GFS/00Z ECMWF AMPLIFY IT IS UNCERTAIN AND CONSIDERED QUESTIONABLE GIVEN THE EXISTING PROGRESSIVE SHORTWAVE PATTERN...INCREASING MID/UPPER LEVEL WIND SPEED WITH LATITUDE...AND RISING MID/UPPER LEVEL HEIGHTS BENEATH THE RIDGE OVER THE SOUTHEAST. THESE CONDITIONS WOULD TEND TO FAVOR LESS AMPLIFICATION OF PROGRESSIVE LOW AMPLITUDE TROUGHS EXITING THE ROCKIES THAN WHAT THE GFS/00Z ECMWF ARE SHOWING. AT THE SAME TIME...THE NAM IS ON THE WEAK/PROGRESSIVE SIDES OF THE GUIDANCE WITH THIS PARTICULAR EVOLUTION ALONG THE NEW ENGLAND COAST...BUT HAS GOOD SUPPORT FROM THE NEW UKMET/NEW ECMWF. THIS APPROACH NEGATES THE OPERATIONAL GFS/00Z ECMWF OVER THE NORTHEAST/NEW ENGLAND/MID-ATLANTIC REGION LATE IN THE PERIOD. ...HURRICANE IDA... ...UPPER LOW OVER N. MEXICO... ...POSSIBLE SURFACE LOW DEVELOPMENT ALONG THE SOUTHEAST/MID-ATLANTIC COAST TUE/WED... PLEASE REFER TO LATEST TPC DISCUSSION/ADVISORY FOR FURTHER INFORMATION REGARDING IDA. MESOSCALE/GLOBAL GUIDANCE CONTINUES TO DISPLAY LARGE SPREAD WITH LOW CONFIDENCE IN ANY PARTICULAR SOLUTION. THE DIFFERENCES APPEAR TO EMANATE FROM HOW THE VARIOUS MODELS ALLOW FOR PHASING OF DIFFERENT STREAMS OF FLOW OVER THE EASTERN CONUS LATE IN THE PERIOD. THE NAM/UKMET/ECMWF SHOW LITTLE OR NO PHASING WITH A MORE NORTHERN STREAM SHORTWAVE TROUGH APPROACHING THE APPALACHIANS...RESULTING IN SLOWER/MORE WESTWARD SURFACE LOW TRACK AS IT MOVES INLAND ALONG THE NORTHERN GULF COAST BEFORE POSSIBLY RECURVING SOUTHEASTWARD...WHILE THE GFS SHOWS CONSIDERABLE PHASING AND THUS NORTHEASTWARD ACCELERATION UP THE SOUTHEAST/MID-ATLANTIC COAST...WITH SUBSEQUENT INTENSIFICATION OVER EASTERN NORTH CAROLINA. THE UKMET IS CLOSEST TO THE TPC OFFICIAL FORECAST THROUGH THE ENTIRE PERIOD INCLUDING SOUTHEASTWARD RECURVATURE...WHILE THE NAM/ECMWF ARE A LITTLE NORTH/NORTHWEST OF THE TPC OFFICIAL FORECAST TRACK BUT ALSO RECURVE THE LOW SOUTHEASTWARD. ...COLD FRONT INFLUENCING THE NORTHWEST MON/MON NGT... ...SHORTWAVE TROUGH AMPLIFICATION OVER THE NORTHWEST TUE/WED... PREFERENCE: GFS/ECMWF THE MODELS SHOW SIMILAR TIMING WITH ARRIVAL OF THE COLD FRONT ALONG THE PACIFIC NORTHWEST COAST BY MONDAY...WITH THE NAM STRONGER THAN THE GFS/ECMWF WITH THE SURFACE LOW ENTERING BRITISH COLUMBIA. THE NAM IS THEN A LITTLE SLOWER THAN THE GFS/ECMWF WITH ARRIVAL OF AN AMPLIFYING SHORTWAVE TROUGH NEARING THE COAST BY LATE WED...WHILE THE NEW UKMET/CANADIAN ARE FASTEST BUT ARE CONSIDERED QUESTIONABLE GIVEN THEIR OCCASIONAL FAST BIAS WITH SYSTEMS ENTERING THE HIGHER LATITUDES OF THE WESTERN NORTH AMERICA. ...MODEL TREND GRAPHICS AT WWW.HPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML... ...500 MB FORECASTS AT WWW.HPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML... JAMES $$