MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1225 PM EDT FRI MAY 08 2015 VALID MAY 08/1200 UTC THRU MAY 12/0000 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 12Z GFS/NAM EVALUATION WITH PRELIMINARY MODEL PREFERENCES ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ NAM/GFS INITIALIZATION ERRORS DO SEEM DEGRADE THEIR SHORT RANGE FORECASTS. CLOSED LOW MOVING INTO THE WEST LATE MONDAY ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: NAM/ECMWF/UKMET COMPROMISE CONFIDENCE: AVERAGE A COMBINATION OF BROAD RIDGING UPSTREAM IN THE PACIFIC ALONG WITH A BLOCKING HIGH ACROSS WESTERN CANADA SHOULD ALLOW THIS SYSTEM TO DIG RATHER THAN NOT, WHICH RULES OUT THE NORTHERN 12Z GFS FROM CONSIDERATION. THE 00Z CANADIAN IS THE MOST SOUTHERLY GUIDANCE -- ITS USUAL BIAS. A COMPROMISE OF THE 12Z NAM/00Z ECMWF/00Z UKMET LOOKS BEST HERE, WHICH IS PREFERRED WITH AVERAGE CONFIDENCE. DEEP CYCLONE MOVING THROUGH THE ROCKIES/PLAINS/MIDWEST ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GFS/ECMWF/CANADIAN COMPROMISE CONFIDENCE: AVERAGE THE 12Z NAM OUTRACES THE REST OF THE GUIDANCE AS THE SYSTEM EMERGES INTO THE HIGH PLAINS LATE SUNDAY WHILE THE 00Z UKMET IS ON THE SRN EDGE OF THE LATEST DETERMINISTIC MODELS. A COMPROMISE OF THE 00Z CANADIAN/12Z GFS/00Z ECMWF REMAINS WITHIN THE BEST 00Z GLOBAL ENSEMBLE LOW CLUSTERING, AND IS PREFERRED WITH AVERAGE CONFIDENCE. SUBTROPICAL STORM ANA ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: CLOSE TO THE 12Z NAM CONFIDENCE: BY DEFAULT/SEE NHC ADVISORIES THE LATEST NHC TRACK IS CLOSE TO A COMPROMISE OF THE 12Z GFS/00Z ECMWF, RESEMBLING THE 12Z NAM THE BEST. FOR THE LATEST INFORMATION ON ANA, SEE NHC ADVISORIES. WEAK FRONTAL WAVE MOVING THROUGH THE GREAT LAKES FRI/SAT ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: NON-GFS COMPROMISE CONFIDENCE: ABOVE AVERAGE THE 12Z GFS CARRIES THE FRONTAL ZONE/WAVE QUICKER THROUGH THE GREAT LAKES FRIDAY NIGHT/SATURDAY THAN THE OTHER GUIDANCE. PREFER THE NON-GFS CONSENSUS HERE WITH ABOVE AVERAGE CONFIDENCE. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... ROTH