MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 147 AM EST SUN FEB 08 2015 VALID FEB 08/0000 UTC THRU FEB 11/1200 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 00Z MODEL EVALUATION INCLUDING PREFERENCES ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ GFS/NAM INITIALIZATION ERRORS DO NOT SEEM TO DEGRADE THEIR SHORT RANGE FORECASTS. TROUGH PROGRESSING INTO THE INTER-MOUNTAIN WEST ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GFS/ECMWF OR UKMET COMPROMISE CONFIDENCE: ABOVE AVERAGE THE 00Z NAM IS SLIGHTLY SLOWER AND DEEPER WITH THIS SYSTEM -- ITS USUAL BIAS. THE 00Z CANADIAN IS QUICKER. THE 00Z UKMET/00Z ECMWF BECOMES MORE POSITIVELY TILTED WITH THIS SYSTEM DUE TO THE INFLUENCE OF ITS STRONGER SHORTWAVE MOVING ACROSS THE PLAINS/MIDWEST/GREAT LAKES. THIS SYSTEM IS ATTEMPTING TO AMPLIFY DUE TO FAIRLY SHARP RIDGING JUST UPSTREAM MOVING INTO THE WEST COAST STRENGTHENING. THE 00Z GFS LOOKS LIKE THE 12Z ECMWF/21Z SREF ENSEMBLE MEANS WHILE THE 12Z ECMWF RESEMBLES THE 00Z GEFS MEAN. TO DEAL WITH THE INCREASING UNCERTAINTY, PREFER A GFS/ECMWF OR UKMET COMPROMISE WITH AVERAGE CONFIDENCE. SHORTWAVE MOVING THROUGH THE NRN PLAINS/GREAT LAKES TUE/WED ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GFS/CANADIAN/ECMWF COMPROMISE CONFIDENCE: AVERAGE THE 00Z UKMET/00Z ECMWF ARE MORE AMPLIFIED THAN THE OTHER GUIDANCE WITH THIS SYSTEM MONDAY NIGHT/TUESDAY MORNING, THOUGH THE ECMWF'S CORRESPONDING SURFACE LOW IS WEAKER/MORE SUPPRESSED THAN THE 00Z UKMET. THE 00Z NAM BEGINS TO LAG THE OTHER GUIDANCE WITH THIS SHORTWAVE'S PROGRESSION TUESDAY NIGHT -- ONE OF ITS KNOWN BIASES. NEITHER THE NAM OR UKMET/ECMWF SOLUTIONS BEFIT THE PATTERN AS THE SYSTEM IS ROUNDING THE NORTHERN SIDE OF A LONG WAVE RIDGE THROUGH QUICK/SUPERGEOSTROPHIC FLOW, WHICH SHOULD LEAD TO LESS AMPLITUDE AND FAVOR GREATER RATHER THAN LESSER PROGRESSION. A COMPROMISE OF THE 00Z CANADIAN/00Z ECMWF/00Z UKMET/00Z GFS IS FAVORED HERE TO DEAL WITH THE INCREASING UNCERTAINTY WITH AVERAGE CONFIDENCE. TROUGH DIGGING THROUGH THE EAST/WRN ATL MONDAY/TUESDAY ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GFS/ECMWF OR UKMET COMPROMISE CONFIDENCE: AVERAGE THE 00Z UKMET/00Z ECMWF BECOMES MORE SOUTHWESTERLY AND AMPLIFIED WITH THIS SYSTEM ACROSS THE SOUTHEAST STARTING LATE MONDAY -- THE UKMET TRENDED NORTHEAST FROM ITS 07/00Z RUN. THE 00Z NAM LOOKS FINE INTO LATE MONDAY BEFORE BECOMING DEEPER/MORE NORTHERLY WITH THE SURFACE LOW THAN THE OTHER GUIDANCE ONCE THE SYSTEM IS OFFSHORE -- ITS USUAL BIAS. A COMPROMISE OF THE 00Z GFS/00Z ECMWF OR 00Z UKMET STAYS TOWARDS THE MIDDLE OF THE DETERMINISTIC AND 12Z GLOBAL ENSEMBLE SPREAD YET ACCOUNTS FOR THE SHIFT IN THE 00Z ECMWF, AND IS PREFERRED WITH AVERAGE CONFIDENCE. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... ROTH