MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 117 PM EDT TUE JUN 02 2015 VALID JUN 02/1200 UTC THRU JUN 06/0000 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 12Z NAM/GFS EVALUATION...INCLUDING PRELIMINARY PREFERENCES ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ WELL DEVELOPED NORTHERN STREAM UPPER LOW ROLLING ACROSS NEW ENGLAND SURFACE LOW PASSING JUST OFF NOVA SCOTIA ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: BLEND OF OPERATIONAL MODELS CONFIDENCE: ABOVE AVERAGE NO SIGNIFICANT MODEL DIFFERENCES WERE NOTED...ABOVE AVERAGE CONFIDENCE EXITS GIVEN THE SHORT TERM NATURE OF THE FORECAST AND VERY GOOD AGREEMENT AMONG THE LATEST GUIDANCE. CLOSED LOW FORECAST TO WEAKEN EWD ACROSS THE SRN APPALACHIANS THROUGH THE END OF THE WORK WEEK ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: BLEND OF 00Z ECMWF/UKMET CONFIDENCE: SLIGHTLY ABOVE AVERAGE THE 12Z NAM/GFS HAVE BOTH TRENDED A BIT FASTER WITH THE EWD PROGRESSION OF THE MID-LEVEL CLOSED LOW TRACKING EAST ACROSS THE SRN APPALACHIANS BY THU EVENING. THE NAM IS THE FASTEST...FOLLOWED BY THE GFS...WITH THE 00Z ECMWF/UKMET LAGGING SLIGHTLY BEHIND BY THU EVENING. THE 00Z CMC IS SLOWEST WITH THE PROGRESSION BY FRI EVENING. ALTHOUGH TRENDS IN MUCH OF THE GUIDANCE HAVE BEEN FASTER...THE ENSEMBLE MEANS...INCLUDING THE 09Z SREF...STILL SUPPORT A PROGRESSION SIMILAR TO THE 00Z ECMWF/UKMET. GIVEN THE SLOW PROGRESSION OF THIS TROUGH TO DATE...AND THE PRESENCE OF RIDGING ACROSS THE WRN ATLANTIC...PREFER TO NOT JUMP ON THE FASTEST SOLUTIONS AT THIS TIME. SHORTWAVE SHEARING OUT ALONG U.S./CANADIAN BOARDER NORTHERN HIGH PLAINS CYCLOGENESIS SOUTHERN STREAM SHORTWAVE EJECTING INTO CENTRAL PLAINS THURSDAY ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: NEAR THE 00Z ECMWF 12Z GFS SECONDARY PREFERENCE AFTER 12Z FRI CONFIDENCE: SLIGHTLY BELOW AVERAGE A COMPLEX SITUATION FORECAST ACROSS THE PLAINS WITHIN SOUTHWEST FLOW ALOFT AND WEAK IMPULSES EJECTING OUT FROM THE WESTERN CONUS. CONVECTIVE DETAILS MUDDLE THE FORECAST AND FEATURES ARE DIFFICULT TO TRACK GIVEN RELIANCE ON YET TO BE SEEN CONVECTIVELY DRIVEN VORTICITY MAXIMA. HOWEVER...THE NAM REMAINS A STRONGER OUTLIER WITH SHORTWAVE ENERGY REACHING THE UPPER MIDWEST EARLY THU MORNING WITH THE GFS FLATTEST OF THE DETERMINISTIC GUIDANCE. THE 00Z ECMWF/UKMET SEEM TO BE IN AGREEMENT WITH EACH OTHER AND THE ENSEMBLE MEANS HERE...BUT THE UKMET APPEARS TO DEVELOP CONVECTIVE FEEDBACK ACROSS THE CNTRL HIGH PLAINS THU MORNING WHICH CONTAMINATES THE FORECAST INTO FRI. THE WEAKER SOLUTION ALOFT IN THE 12Z GFS MAY BE CAUSING THE FRONTAL BOUNDARY ACROSS THE PLAINS TO BE TOO FAR NORTH. OFTEN TIMES IT SEEMS THE MODELS CAN BE TOO FAR NORTH WITH FRONTS/CONVECTION IN THESE TYPES OF SETUPS ACROSS THE PLAINS. THE 00Z ECMWF APPEARS TO BE THE MOST RELIABLE MODEL FROM TODAY THROUGH FRI EVENING...WITH THE 12Z GFS A SECOND CHOICE FOR FRI ACROSS THE PLAINS AS EARLIER DIFFERENCES ARE NO LONGER AN ISSUE BACK ACROSS THE PLAINS. UPPER TROUGH RELOADING OVER THE WEST BY WED/THU ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: NON 00Z UKMET BLEND CONFIDENCE: ABOVE AVERAGE ONLY MINOR PLACEMENT/TIMING DIFFERENCES EXIST WITH A CLOSED LOW FORECAST TO FORM OVER CALIFORNIA BY MID-DAY THURSDAY. THE 00Z UKMET DOES STAND OUT ENOUGH BY FRI EVENING HOWEVER...WITH A SOMEWHAT MORE OPEN AND NEWD PROGRESSION. GIVEN GOOD AGREEMENT OUTSIDE OF THE 00Z UKMET...THE PREFERENCE IS FOR A NON 00Z UKMET BLEND OF MODELS. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... OTTO