MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1124 PM EST SAT NOV 29 2014 VALID NOV 30/0000 UTC THRU DEC 03/1200 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 00Z NAM/GFS EVALUATION WITH PRELIMINARY MODEL PREFERENCES ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ NAM/GFS INITIALIZATION ERRORS DO NOT SEEM TO DEGRADE THEIR SHORT RANGE FORECASTS. DEEP CYCLONE APPROACHING CALIFORNIA ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: NON-CANADIAN COMPROMISE CONFIDENCE: ABOVE AVERAGE THE GUIDANCE SHOWS RELATIVELY GOOD AGREEMENT WITH THIS FEATURE. THE ONE THAT DOES NOT BELONG IS THE 12Z CANADIAN, WHICH IS SLOWER WITH PROGRESSING THE SYSTEM EASTWARD, ONE OF ITS USUAL BIASES. A COMPROMISE OF THE 00Z NAM/00Z GFS/12Z UKMET/12Z ECMWF WOULD BE IDEAL HERE, WHICH MATCH WELL WITH THE 12Z ECMWF/18Z GEFS MEANS. UPPER TROUGH TRYING TO DIG TOWARDS THE GREAT LAKES WED ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GFS/ECMWF/CANADIAN COMPROMISE CONFIDENCE: SLIGHTLY ABOVE AVERAGE THE 12Z UKMET IS FAIRLY SHARP WITH THIS FEATURE MOVING ACROSS THE NORTHERN STATES, WHICH DOESN'T MAKE MUCH SENSE CONSIDERING HOW BROAD THE UPPER TROUGH IS ACROSS MUCH OF CANADA TUESDAY INTO WEDNESDAY. THE 00Z NAM IS THE SLOWEST WITH ITS PROGRESSION -- ITS USUAL BIAS -- THOUGH IT IS ALSO THE SHALLOWEST DESPITE STRONGER UPSTREAM RIDGING ACROSS WESTERN CANADA (WHICH DOES NOT FOLLOW). A COMPROMISE OF THE 00Z GFS/12Z ECMWF/12Z CANADIAN FITS THE 12Z ECMWF/18Z GEFS MEAN SOLUTIONS THE BEST, AND IS PREFERRED WITH SLIGHTLY ABOVE AVERAGE CONFIDENCE. SYSTEM MOVING BY NEW ENGLAND SUNDAY NIGHT ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: ECMWF/NAM/UKMET COMPROMISE CONFIDENCE: ABOVE AVERAGE THERE IS SLIGHT TIMING DIFFERENCE WITH THE UPPER TROUGH AND ASSOCIATED COLD FRONT, WITH THE 00Z GFS/18Z GEFS MEAN SLIGHTLY OUTPACING THE REMAINDER OF THE GUIDANCE, AND THE 12Z CANADIAN THE SLOWEST -- BOTH FITTING THEIR USUAL BIASES. A COMPROMISE OF THE 12Z ECMWF/00Z NAM/12Z UKMET WILL OFFSET THE ABOVE MODEL BIASES, AND IS PREFERRED WITH ABOVE AVERAGE CONFIDENCE. BAHAMIAN MID-LEVEL LOW/TUTT CELL WED AM ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GFS/ECMWF COMPROMISE CONFIDENCE: ABOVE AVERAGE SHORTWAVE ENERGY FROM THE SOUTHERN STREAM OF THE WESTERLIES ACROSS THE SOUTHERN STATES ATTEMPTS TO FORM AN UPPER LEVEL LOW OVER THE BAHAMAS LATE TUESDAY/EARLY WEDNESDAY. THE 00Z NAM IS THE STRONGEST -- ITS USUAL BIAS -- WHILE THE 12Z UKMET/12Z CANADIAN ARE THE WEAKEST WITH THIS FEATURE. CONSIDERING HOW FAR NORTH THE POLAR JET STREAM IS AT THIS TIME, IT MAKES SENSE THAT AN UPPER LOW WOULD TRY TO DEVELOP OFFSHORE FLORIDA, WHICH IS ADVERTISED BY THE 12Z ECMWF/18Z GEFS MEAN SOLUTIONS. A COMPROMISE OF THE 00Z GFS/12Z ECMWF IS PREFERRED WITH ABOVE AVERAGE CONFIDENCE. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... ROTH