MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1127 AM EST FRI FEB 27 2015 VALID FEB 27/1200 UTC THRU MAR 03/0000 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. UPPER LOW/TROUGH DRIFTING THROUGH CA SAT-MON SHORTWAVE APPROACHING THE NRN CONTINENTAL DIVIDE MON ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GFS/UKMET COMPROMISE CONFIDENCE: SLIGHTLY ABOVE AVERAGE THE 12Z NAM/00Z CANADIAN ARE QUICKER TO MOVE THE UPPER TROUGH EASTWARD, WHILE THE 00Z UKMET IS ON THE SLOW SIDE. BELIEVE THE UKMET AND NAM ARE TOO FAST HERE SINCE ENERGY KEEPS TRYING TO DIG INTO THE BACKSIDE OF THE TROUGH, KEEPING IT SLOW-MOVING. HOWEVER, THE 00Z ECMWF TRIES TO PHASE THE ENTIRE UPPER TROUGH LATE MONDAY, WHICH IS A MISTAKE OCCASIONALLY SEEN IN THE GUIDANCE. FOR NOW, PREFER AN IDEA OF TWO SEPARATE STREAMS OF THE WESTERLIES, WHICH IS BEST REFLECTED IN A COMPROMISE OF THE 12Z GFS AND 00Z UKMET SOLUTIONS. BOUNDARY IN THE SOUTHERN PLAINS ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GFS/UKMET/ECMWF COMPROMISE CONFIDENCE: AVERAGE LINGERING DETAIL ISSUES CONTINUE WITH THE PLACEMENT OF A FRONTAL BOUNDARY IN TX SUNDAY. THE 00Z CANADIAN IS THE FARTHEST SOUTH DUE TO ITS QUICKER FRONTAL PROGRESSION ACROSS THE MIDWEST/MISSISSIPPI VALLEY, WHICH WAS NOT PREFERRED UP NORTH. THE REMAINDER OF THE GUIDANCE SHOW PLAUSIBLE SOLUTIONS, WITH THE GFS FARTHER SOUTH THAN SEEN IN ITS RUN FROM THIS TIME YESTERDAY. TAKING THE CONVERGING GUIDANCE AS A GUIDE, PREFER A COMPROMISE OF THE GFS/UKMET/ECMWF WITH AVERAGE CONFIDENCE. NORTHERN STREAM SHORTWAVE CROSSING NEW ENGLAND MON ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: ECMWF/UKMET COMPROMISE CONFIDENCE: SLIGHTLY ABOVE AVERAGE THE 12Z GFS WAS ON THE SLOW SIDE OF THE GUIDANCE WITH THIS SYSTEM, WHILE THE 12Z NAM/00Z CANADIAN WERE QUICK -- SIMILAR TO THE GUIDANCE DISTRIBUTION THIS TIME YESTERDAY. THE 00Z ECMWF/06Z GEFS/09Z SREF MEANS PREFERRED AN INTERMEDIATE TIMING, ALONG THE LINES OF THE 00Z ECMWF AND 00Z UKMET. THIS PREFERENCE IS PREFERRED WITH SLIGHTLY ABOVE AVERAGE CONFIDENCE. SHORTWAVE MOVING ACROSS PA LATE SATURDAY ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GENERAL MODEL COMPROMISE CONFIDENCE: ABOVE AVERAGE THE GUIDANCE SHOWS GOOD AGREEMENT WITH THIS SYSTEM. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... ROTH