MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1255 AM EDT TUE APR 22 2014 VALID APR 22/0000 UTC THRU APR 25/1200 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 00Z NAM/GFS EVALUATION AND PRELIMINARY PREFERENCES ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ NAM/GFS INITIALIZATION ERRORS DO NOT APPEAR TO SIGNIFICANTLY AFFECT THEIR LARGE SCALE OUTPUT. COLD FRONT MOVING THROUGH THE EAST TODAY CLOSED MID-LEVEL LOW FORMING NEAR NEW ENGLAND MID TO LATE WEEK ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GENERAL MODEL CONSENSUS CONFIDENCE: SLIGHTLY ABOVE AVERAGE THE LATEST MODEL RUNS CONTINUE TO CONVERGE UPON A COMMON SOLUTION...ALTHOUGH SMALLER DETAIL DIFFERENCES REMAIN. THE 12Z ECMWF AND CMC ARE BOTH A BIT MORE POTENT WITH A BALL OF MID-LEVEL VORTICITY JUST OFF OF THE NEW ENGLAND COAST ON WED...BUT NOT UNREASONABLY SO. THE OVERALL TREND HAS BEEN SLIGHTLY SLOWER/WEST WITH THE CLOSED LOW THAT FORMS LATER THIS WEEK OFF OF THE COAST...BUT THE MODELS ARE WITHIN THE GLOBAL ENSEMBLE SPREAD WHICH IS RELATIVELY TIGHTLY CLUSTERED. THE 00Z GFS AND 12Z ECMWF ARE LIKELY CLOSEST TO THE MIDDLE OF THE REMAINING MODEL SPREAD...BUT THIS SPREAD IS SMALL ENOUGH THAT IT IS DIFFICULT TO REMOVE ONE MODEL FROM THE PREFERENCE. LARGE TROUGH AFFECTING THE WEST TODAY...AND THE PLAINS ON WED ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: BLEND OF 00Z NAM...00Z GFS...12Z ECMWF CONFIDENCE: AVERAGE THE MODELS SHOW SOME WOBBLING ABOUT A COMMON SOLUTION GOING BACK THROUGH THE PAST FEW RUNS...REGARDING THE UPPER TROUGH ADVANCING OUT INTO THE PLAINS ON WED...AND DEVELOPING LOW PRESSURE AT THE SURFACE. THE 00Z NAM...GFS..AND 12Z ECMWF SHOW SIMILAR EVOLUTIONS...WITH THE 00Z NAM A BIT EAST OF THE GFS/ECMWF WITH THE SURFACE / 850 MB LOW ACROSS S-CNTRL CANADA THU MORNING. THE 12Z UKMET/CMC ARE FARTHER SOUTH...NOT IN AGREEMENT WITH THE ENSEMBLE MEANS...AND ARE FARTHER WEST BY FRI MORNING. THE BETTER ENSEMBLE SUPPORT IS WITH THE NAM/GFS/ECMWF. BROAD TROUGH REACHING THE PACIFIC NORTHWEST THURSDAY ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GENERAL MODEL CONSENSUS CONFIDENCE: SLIGHTLY ABOVE AVERAGE MODELS CONTINUE IN GOOD AGREEMENT ON THE LARGE SCALE. SMALL DETAIL DIFFERENCES WILL CONTINUE TO EXIST WITH THE SMALLER SCALE SHORTWAVE PLACEMENT DETAILS...BUT THERE IS DECENT AGREEMENT ON THE LARGE SCALE EVOLUTION ACROSS THE WEST BY FRI MORNING. A GENERAL MODEL COMPROMISE CAN BE USED TO IRON OUT LINGERING DETAIL DIFFERENCES. www.wpc.ncep.noaa.gov/html/model2.shtml... OTTO