MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1103 AM EST FRI NOV 21 2014 VALID NOV 21/1200 UTC THRU NOV 25/0000 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 12Z GFS/NAM EVALUATION WITH PRELIMINARY MODEL PREFERENCES ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ GFS/NAM INITIALIZATION ERRORS DO NOT SEEM TO DEGRADE THIS SHORT RANGE FORECASTS. SHORTWAVES MOVING THROUGH THE NORTHWEST & THEIR CONTRIBUTION TO THE MIDWEST TROUGH ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GFS/ECMWF COMPROMISE CONFIDENCE: ABOVE AVERAGE SUBTLE DIFFERENCES WITH A WAVE OF LOW PRESSURE AND ITS PARENT SHORTWAVE MOVING TOWARDS THE PACIFIC NORTHWEST SATURDAY ARE EASILY RESOLVED WITH AN ECMWF/GFS COMPROMISE, CONSIDERING THE SPLIT SEEN IN THE GEFS/CANADIAN AND ECMWF ENSEMBLE MEMBER CAMPS. OTHERWISE, THE SOUTHERN STREAM COMPONENT OF THE MIDWEST TROUGH IS SHARPER ALOFT WITHIN THE 12Z NAM/12Z GFS GUIDANCE THAN THE OTHER AVAILABLE GUIDANCE. THE BEST 00Z ENSEMBLE LOW CLUSTERING WITH THE LOW LIFTING UP TOWARDS THE GREAT LAKES RULES OUT THE 12Z NAM/00Z UKMET/00Z CANADIAN FROM CONSIDERATION. ALOFT, THE NORTHERN STREAM COMPONENT OF THE MIDWEST TROUGH APPEARS TOO WEAK IN THE 00Z ECMWF. UTILIZING A COMPROMISE OF THE 00Z ECMWF/12Z GFS DEALS WITH THIS ISSUE EFFECTIVELY. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... ROTH