MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1143 PM EST SUN MAR 05 2017 VALID MAR 06/0000 UTC THRU MAR 09/1200 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 SEEM TO DEGRADE THEIR SHORT RANGE FORECASTS. DEEP CYCLONE MOVING BY THE CENTRAL U.S./CANADA BORDER MONDAY EVE COLD FRONT MOVING THROUGH THE PLAINS AND EAST MON TO WED ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: HALFWAY BETWEEN THE 00Z GFS AND 12Z ECMWF CONFIDENCE: AVERAGE ENSEMBLE SPAGHETTI HEIGHTS CONTINUE TO SHOW THE GFS AS FASTER AND THE ECMWF AS SLOWER WITH THIS SYSTEM. THIS HAS BEEN THE CASE FOR THE PAST FEW DAYS AND WHILE THERE HAS BEEN SOME CONVERGENCE IN THE 500 MB LOW STRENGTH AND TIMING AS WELL AS FRONTAL TIMING DOWNSTREAM ACROSS THE GREAT LAKES...THE DIFFERENCES REMAIN. THE IDEA HAS BEEN TO STAY IN THE MIDDLE OF THE EDGES OF THE ENSEMBLE DISTRIBUTION WHICH IS CURRENTLY BETWEEN THE 00Z GFS AND 12Z ECMWF. THE ENSEMBLES DO NOT SUPPORT THE SHAPE/POSITION OF THE 12Z CMC OR 00Z NAM AT 500 MB. THE 12Z UKMET 500 LOW IS A BIT SOUTH OF THE LATEST ENSEMBLE MEANS VALID 12Z/07. BEYOND 12Z/07...THE TIMING DIFFERENCES BETWEEN THE 00Z GFS AND 12Z ECMWF SHRINK WITH ONLY THE NAM SHOWING SIGNIFICANTLY SLOWER WITH THE COLD FRONT ACROSS THE LOWER MISSISSIPPI VALLEY. ZONAL FLOW INTO THE PACIFIC NORTHWEST TUE/WED SURFACE LOW REACHING THE PACIFIC NORTHWEST ON TUESDAY ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 00Z GFS/12Z ECMWF BLEND CONFIDENCE: ABOVE AVERAGE THE 12Z UKMET AND 12Z CMC SHOW AS NEAR OUTLIERS WITHIN THE 12Z/05 ENSEMBLE DISTRIBUTION OFF OF THE PACIFIC NORTHWEST. THIS LEAVES THE 00Z NAM WHICH IS ON THE DEEPER/SOUTH SIDE WITH TROUGHING OFF OF THE PACIFIC NORTHWEST COAST BY WED...AND THE 00Z GFS AND 12Z ECMWF WITH THE 12Z ECMWF FARTHEST NORTH. THE DIFFERENCE STEMS FROM...AT LEAST IN PART...THE DEGREE OF ENERGY THAT KICKS OUT FROM A CLOSED LOW FORECAST NEAR 35N 165W. RUN TO RUN CONTINUITY HAS BEEN POOR IN THE ENSEMBLES AND THE LATEST GEFS/ECMWF MEANS SHOW BETWEEN THE 00Z GFS AND 12Z ECMWF. THEREFORE...A BLEND BETWEEN THE GFS/ECMWF IS PREFERRED...AT LEAST UNTIL 12Z/09...THE END OF THE SHORT RANGE PERIOD...WHEN DIFFERENCES ARE WITHIN TOLERANCE. UPPER LEVEL SYSTEM SHEARING THROUGH THE SOUTHEAST EARLY TODAY ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GENERAL MODEL COMPROMISE CONFIDENCE: ABOVE AVERAGE THE MODELS SHOW SIMILARLY WITH THIS SYSTEM. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... OTTO