MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1229 PM EDT WED APR 16 2014 VALID APR 16/1200 UTC THRU APR 20/0000 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 12Z NAM/GFS EVALUATION WITH PRELIMINARY MODEL PREFERENCES ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ NAM/GFS INITIALIZATION ERRORS DO NOT SEEM TO DEGRADE THEIR SHORT RANGE FORECASTS. SYSTEM APPROACHING THE PACIFIC NORTHWEST SAT SYSTEM MOVING ACROSS SOUTHERN CANADA FRI/SAT SYSTEM MOVING ACROSS THE SOUTHWEST FRI/SAT ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GENERAL MODEL COMPROMISE CONFIDENCE: ABOVE AVERAGE THE GUIDANCE SHOWS MINIMAL ISSUES WITH THE PROGRESSION AND DEPTH OF THESE SYSTEMS, AT THE SURFACE OR ALOFT. A GENERAL MODEL COMPROMISE IS PREFERRED WITH ABOVE AVERAGE CONFIDENCE CONSIDERING THE GOOD MODEL AGREEMENT. CLOSED LOW DEVELOPING NEAR FL FRI NIGHT/SAT ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GFS/ECMWF COMPROMISE CONFIDENCE: AVERAGE THE SYNOPTIC PATTERN FEATURES A NORTHERN STREAM SLOWLY SHIFTING NORTHWARD IN ADVANCE OF A SYSTEM APPROACHING WESTERN NORTH AMERICA SATURDAY. THIS CHANGE IN THE NORTHERN STREAM ALLOWS THE POSSIBILITY OF CLOSED SYSTEMS ALOFT IN THE SOUTHERN STREAM, AND THE AVAILABLE GUIDANCE BEARS THIS OUT. THIS SOUTHEASTERN SYSTEM HAS A CHANCE TO DIG/AMPLIFY INTO FRIDAY NIGHT BEFORE THE UPSTREAM SYSTEM IN THE SOUTHWEST WEAKENS. BOTH THE 00Z ECMWF/06Z GEFS MEANS IMPLY A MORE SOUTHERN SOLUTION IS ADVISED, SIMILAR TO THEIR OPERATIONAL RUNS, WHICH FAVORS THE ABOVE IDEA. THE 12Z NAM IS MORE SOUTHERLY WHILE THE 00Z CANADIAN/00Z UKMET ARE MORE NORTHERLY. THE 12Z GFS IS BEING CONTAMINATED BY GRIDSCALE FEEDBACK, AS A PARTICULARLY STRONG BULL'S EYE MOVES INTO FL'S BIG BEND INTO THE WESTERN SUBTROPICAL ATLANTIC MIDDAY FRIDAY, WHICH ACTS TO OPEN UP THE GFS SOLUTION AT THE 500 HPA AND 700 HPA LEVELS FRIDAY AFTERNOON. THIS IS LEADING TO A QUICKER SOLUTION AND MORE DELAYED CLOSURE OF THE 500 HPA AND 700 HPA LOWS. THE SYSTEM SHOULD MAINTAIN SOME PROGRESSION DUE TO MOVEMENT UPSTREAM ACROSS SOUTHWEST/SOUTHERN ROCKIES, BUT THE GFS IS LIKELY TOO QUICK. TO ACCOUNT FOR THIS, FAVOR A COMPROMISE OF THE 12Z GFS/00Z ECMWF WITH CONFIDENCE NO BETTER THAN AVERAGE CONSIDERING THE EXISTING MODEL SPREAD. SYSTEM MOVING BY NEW ENGLAND FRI NIGHT/SAT MORNING ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GENERAL MODEL COMPROMISE CONFIDENCE: AVERAGE THERE ARE SLIGHT ISSUES ALOFT WITH THE SYSTEM'S PROGRESSION AND SHARPNESS, BUT FOR THE MOST PART, THE MASS FIELD ISSUES ARE QUITE SMALL. A GENERAL MODEL COMPROMISE IS PREFERRED HERE WITH AVERAGE CONFIDENCE CONSIDERING THE EXISTING MODEL SPREAD AND ITS PROGRESSIVE NATURE. www.wpc.ncep.noaa.gov/html/model2.shtml... ROTH