MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 228 PM EDT TUE MAY 24 2016 VALID MAY 24/1200 UTC THRU MAY 28/0000 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 12Z MODEL EVALUATION WITH PREFERENCES/CONFIDENCE LEVELS ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ NAM/GFS INITIALIZATION ERRORS DO NOT APPEAR TO DEGRADE THEIR SHORT RANGE FORECASTS. SOUTHWEST TO CENTRAL PLAINS UPPER LOW SYSTEM DIVING INTO THE PACIFIC NORTHWEST FRIDAY CLOSED LOW LIFTING INTO THE NORTHEAST TUE/WED ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ THE GUIDANCE SHOWS REASONABLE AGREEMENT WITH THESE SYSTEMS. TO DEAL WITH LINGERING DETAIL ISSUES, PREFER A COMPROMISE OF THE AVAILABLE DETERMINISTIC GUIDANCE WITH ABOVE AVERAGE CONFIDENCE. PAIR OF UPPER LOWS ALONG CENTRAL US/CANADIAN BORDER ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: NON-UKMET COMPROMISE CONFIDENCE: ABOVE AVERAGE THE 00Z/12Z UKMET WERE DEEP OUTLIERS WITH THE FIRST SYSTEM, WHICH IS MOST NOTICEABLE AT 700 HPA. OTHERWISE, IT BECOMES TOO RETROGRESSIVE THE SECOND/WESTERN SYSTEM, A BIAS SOMETIMES DISPLAYED IN ALL THE MODEL GUIDANCE. PREFER A COMPROMISE OF THE 12Z GFS/12Z NAM/00Z CANADIAN/00Z ECMWF WITH ABOVE AVERAGE CONFIDENCE. UPPER LOW DRIFTING ABOUT THE FL STRAITS & ITS CONVECTIVE SURFACE REFLECTION ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: NON-NAM COMPROMISE CONFIDENCE: AVERAGE MOST OF THE GUIDANCE DEVELOPS AN INVERTED TROUGH NEAR AND NORTH OF THE BAHAMAS IN A DIVERGENT AREA ALOFT NORTH OF AN UPPER LOW, A CONVECTIVELY FAVORABLE ENVIRONMENT. WITH THE UPPER LOW ITSELF, THE GUIDANCE SHOWS GOOD AGREEMENT, THOUGH THE 12Z NAM IS A BIT DEEP -- ITS USUAL BIAS AT THIS TIME RANGE. BOTH THE 12Z NAM AND 12Z CANADIAN DEVELOP A SURFACE LOW WITH A CLOSED ISOBAR, THOUGH THE 12Z NAM IS MORE RETROGRESSIVE -- A COMMON MODEL BIAS. AT LEAST ONE-THIRD OF THE 00Z GLOBAL ENSEMBLE MEMBERS DEPICT A LOW NORTH OF THE BAHAMAS FRIDAY MORNING, IN A POSITION WHICH BEST MATCHES THE 00Z/12Z CANADIAN RUNS. IN CASE THE CANADIAN IS TOO STRONG, PREFER A COMPROMISE OF THE 12Z CANADIAN, 12Z GFS, 12Z UKMET, AND 12Z ECMWF HERE WITH AVERAGE CONFIDENCE. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... ROTH