MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1142 PM EST WED NOV 12 2014 VALID NOV 13/0000 UTC THRU NOV 16/1200 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 00Z NAM/GFS EVALUATION WITH PRELIMINARY PREFERENCES ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ NAM/GFS INITIALIZATION ERRORS DO NOT APPEAR TO DEGRADE ITS SHORT RANGE FORECASTS. UPPER TROUGHING ACROSS THE WRN U.S. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 00Z NAM...12Z ECMWF COMPROMISE CONFIDENCE: SLIGHTLY BELOW AVERAGE SPREAD REMAINS WITH THE SOUTHWARD PROGRESSION AND DEPTH OF A VERY POSITIVELY-TILTED UPPER LEVEL TROUGH THROUGH THE REGION. SOME OF THE DIFFERENCES BY SAT ACROSS THE INTERIOR WEST CAN BE TRACED BACK TO A WEAK SHORTWAVE FEATURE CURRENTLY OVER THE ARCTIC OCEAN ON THE NORTH SIDE OF A CLOSED MID-LEVEL RIDGE OVER THE NORTHWEST TERRITORIES. MODEL INITIALIZATION APPEARS REASONABLE WITH THE FLOW ACROSS WRN NORTH AMERICA...AND INDIVIDUAL MODEL TRENDS ARE PRETTY CONSISTENT. ENSEMBLE SPREAD AND THEIR MEANS HELPS MAKE A DECISION FOR THE MIDDLE TOWARD THE NAM/ECMWF. LOW AMPLITUDE SHORTWAVE MOVING INTO THE SRN PLAINS BY SAT MORNING ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GENERAL MODEL COMPROMISE CONFIDENCE: SLIGHTLY ABOVE AVERAGE WHILE THE 12Z UKMET IS A BIT STRONGER/SLOWER WITH A MID-LEVEL SHORTWAVE MOVING THROUGH THE SOUTHWEST U.S....THE DIFFERENCES SMOOTH OUT BY SAT MORNING AS THE FEATURE APPROACHES THE PLAINS. A GENERAL MODEL COMPROMISE IS PREFERRED AS ANY REMAINING DIFFERENCES ARE SMALL. SURFACE LOW FORMING OFF OF THE MID-ATLANTIC COAST AND TRACKING JUST EAST OF THE 40/70 BENCHMARK FRI MORNING ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 00Z GFS / 12Z ECMWF BLEND CONFIDENCE: AVERAGE THERE HAS BEEN A NWWD OR WWD TREND WITH A SURFACE LOW FORECAST TO TRACK JUST EAST OF THE BENCHMARK FRI MORNING SEEN IN THE 12Z/12 ENSEMBLE SCATTER LOW PLOTS AND IN THE DETERMINISTIC GUIDANCE OVER THE PAST 24 HOURS OF RUNS. THE 00Z NAM IS ON THE STRONGER SIDE OF THE SPREAD...EDGE OF THE ENSEMBLES AND CLOSER TO THE COAST COMPARED TO THE REMAINING MODELS. GIVEN THE TRENDS HOWEVER...THE MORE NRN GFS SHOULD BE INCLUDED IN A BLEND...ALONG WITH THE 12Z ECMWF WHICH REMAINS A BIT FARTHER SOUTH/OFFSHORE. DIFFERENCES ALOFT ARE QUITE MINOR. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... OTTO