MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 132 AM EST FRI FEB 26 2016 VALID FEB 26/0000 UTC THRU FEB 29/1200 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 00Z MODEL EVALUATION WITH PREFERENCES/CONFIDENCE ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ NAM/GFS INITIALIZATION ERRORS DO NOT SEEM TO DEGRADE THEIR SHORT RANGE FORECASTS. SHORTWAVE MOVING INTO THE WEST SUNDAY/MONDAY ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GFS/ECMWF COMPROMISE CONFIDENCE: AVERAGE THE NEXT SYSTEM RIPPLING THROUGH THE QUASI-ZONAL FLOW PATTERN IN THE LOWER 48 MAKES LANDFALL SUNDAY NIGHT. THE 00Z GFS IS THE SLOWEST PIECE OF GUIDANCE WHILE THE 00Z CANADIAN IS THE QUICKEST. COMPLICATING MATTERS IS THAT THIS SYSTEM IS UNDERCUTTING A NORTHERN STREAM RIDGE ACROSS WESTERN CANADA, WHICH COULD ALLOW THE SYSTEM TO CLOSE OFF IN THE MID-LEVELS. THIS IDEA ELIMINATES THE 00Z NAM/00Z CANADIAN FROM CONSIDERATION, WHICH WERE THE FLATTEST ALOFT, THOUGH THE CANADIAN SHOWS A STRONGER SOLUTION WITH THIS SYSTEM THAN SEEN ON ITS 12Z RUN. THE ENSEMBLE MEANS ARE EQUALLY FLAT DUE TO THE DISPERSION OF THEIR ENSEMBLE MEMBERS. OVERALL, THE 00Z ECMWF/00Z GFS FIT THE FLOW PATTERN BEST SO A COMPROMISE OF THE TWO IS PREFERRED WITH AVERAGE CONFIDENCE. SHORTWAVE MOVING THROUGH SOUTH-CENTRAL CANADA SUN/MON FRONT DROPPING INTO THE NORTHERN PLAINS SUN NIGHT/MON ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: NAM/ECMWF COMPROMISE CONFIDENCE: AVERAGE SHORTWAVE DIFFERENCES IN CANADA LEAD TO FRONTAL TIMING ISSUES, WITH THE 00Z GFS THE QUICKEST AND THE 00Z CANADIAN THE SLOWEST. THE 12Z ECMWF/18Z GEFS MEANS ARE SLIGHTLY OUT OF SYNC, WHICH DOES NOT HELP MATTERS. THE 00Z NAM/00Z ECMWF SPLIT THE DIFFERENCES SEEN IN THE GUIDANCE, WHICH IS PREFERRED WITH AVERAGE CONFIDENCE. SHORTWAVE CROSSING THE MIDWEST SUNDAY ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: SLIGHTLY QUICKER THAN THE ECMWF/CANADIAN CONFIDENCE: SLIGHTLY BELOW AVERAGE THE 00Z GFS/00Z NAM OUTRACE THE OTHER GUIDANCE WITH THIS SYSTEM -- A BIAS SOMETIMES SEEN WITH THE GFS -- WHILE THE 00Z UKMET IS THE SLOWEST/DEEPEST. THE SYSTEM IS MOVING THROUGH QUICK FLOW UNDER THE BASE OF A BROAD TROUGH IN EASTERN/CENTRAL CANADA, WHICH SHOULD RULE OUT ANYTHING OVERLY SHARP/DEEP SUCH AS THE ECMWF IS PORTRAYING. HOWEVER, SHORTWAVE MOVING AROUND THE CANADIAN MID-LEVEL CYCLONE IS IMPORTANT IN THIS SYSTEM'S EVOLUTION AS DIFFERENCES WITH THIS SHORTWAVE HAVE PARTIALLY CAUSED THESE PROGRESSION ISSUES. THE 12Z ECMWF/00Z GEFS MEANS SHOW DISPARATE SOLUTIONS GENERALLY SUPPORTING THEIR OPERATIONAL RUNS. A COMPROMISE OF THE TWO EXTREMES, SIMILAR TO A SOLUTION SOMEWHAT QUICKER THAN THE 00Z ECMWF/00Z CANADIAN, IS THE PRUDENT CHOICE FOR NOW. THIS SOLUTION IS PREFERRED WITH SLIGHTLY BELOW AVERAGE CONFIDENCE. FRONT MOVING INTO NEW ENGLAND EARLY SUNDAY SHORTWAVE MOVING THROUGH THE SOUTHEAST SATURDAY ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ THE GUIDANCE SHOWS GOOD AGREEMENT WITH THIS SYSTEMS, SO PREFER A GENERAL MODEL COMPROMISE WITH ABOVE AVERAGE CONFIDENCE. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... ROTH