MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1130 AM EST TUE NOV 11 2014 VALID NOV 11/1200 UTC THRU NOV 15/0000 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 12Z NAM/GFS EVALUATION WITH PRELIMINARY MODEL PREFERENCES ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ NAM/GFS INITIALIZATION ERRORS DO NOT SEEM TO DEGRADE THEIR SHORT RANGE FORECASTS. TROUGH NEAR THE WESTERN US/CANADIAN BORDER ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GFS/UKMET COMPROMISE CONFIDENCE: ABOVE AVERAGE THE 00Z ECMWF IS QUICKER IN SWINGING THIS SYSTEM SOUTH TO SOUTHEASTWARD INTO THE NORTHERN CONTINENTAL DIVIDE, WHILE THE 00Z CANADIAN IS THE LEAST PROGRESSIVE TO THE SOUTH -- ONE OF ITS BIASES. THERE IS NO OBVIOUS KICKER SHORTWAVE UPSTREAM, SO PLACED MINIMAL WEIGHT ON THE 00Z ECMWF. A COMPROMISE OF THE 00Z UKMET/12Z GFS NAM APPEARS BEST WITHIN THE 500 HPA AND 700 HPA PATTERN, WITHIN 5400 METER 500 HPA HEIGHT GLOBAL ENSEMBLE SPAGHETTI PLOTS, AND MATCHES UP WELL WITH THE 00Z ECMWF/06Z GEFS/09Z SREF ENSEMBLE MEANS. SHORTWAVE MOVING THROUGH THE SOUTHWEST FRIDAY ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: NON-NAM COMPROMISE CONFIDENCE: ABOVE AVERAGE AS IT MOVES INLAND NEAR THE OR/CA BORDER, THE 12Z NAM/00Z UKMET ARE AMONGST THE STRONGER GUIDANCE. ULTIMATELY, THE 12Z NAM BECOMES A SLOW OUTLIER WITH THIS SYSTEM ON FRIDAY -- ITS USUAL BIAS. SINCE THE FLOW PATTERN IT IS EMBEDDED WITHIN IS QUASI-ZONAL, PREFER THE QUICKER AND WEAKER GFS/ECMWF/CANADIAN/UKMET GUIDANCE WITH THIS SYSTEM. EASTERN UNITED STATES ~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: NON-CANADIAN COMPROMISE CONFIDENCE: ABOVE AVERAGE THE 00Z CANADIAN IS SLIGHTLY DEEPER WITH THE SHORTWAVE MOVING THROUGH SOUTHEAST CANADA FRIDAY, WHICH CAUSES CYCLOGENESIS OFF THE MID-ATLANTIC STATES THURSDAY PRIOR TO THE REMAINDER OF THE GUIDANCE, AND THEN EJECTS THE LOW MUCH MORE TO THE NORTHEAST, LYING ON THE NORTHEAST FRINGE OF THE 00Z ENSEMBLE LOW ENVELOPE. THE GFS/NAM/ECMWF/UKMET SHOW GOOD AGREEMENT WITH THE ENSEMBLE MEANS/BEST LOW CLUSTERING WITH THIS SYSTEM. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... ROTH