MODEL DIAGNOSTIC DISCUSSION...AMENDED NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1125 AM EST THU FEB 26 2015 VALID FEB 26/1200 UTC THRU MAR 02/0000 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 12Z NAM/GFS EVALUATION AND PRELIMINARY MODEL PREFERENCES ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ NAM/GFS INITIALIZATION ERRORS DO NOT SEEM TO DEGRADE THEIR SHORT RANGE FORECASTS. UPPER LOW DEVELOPING NEAR L.A. LATE SUNDAY ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GFS/ECMWF COMPROMISE CONFIDENCE: ABOVE AVERAGE THE 00Z CANADIAN/00Z UKMET LOOK SLOW WITH THIS SYSTEM'S PROGRESSION WHEN COMPARED TO THE OTHER GUIDANCE, INCLUDING THE 00Z ECMWF/06Z GEFS/09Z SREF MEANS. THE 12Z NAM LOOKS MUCH TOO SHARP WITH THIS SYSTEM OFFSHORE AS THE OVERALL APPEARANCE OF THE UPPER TROUGH WOULD FAVOR A SOLUTION WHICH IS SOMEWHAT BROAD. THE 00Z ECMWF/06Z GEFS/09Z SREF MEANS SUPPORT A COMPROMISE OF THE 00Z ECMWF/12Z GFS, WHICH IS FAVORED WITH ABOVE AVERAGE CONFIDENCE. BOUNDARY IN THE SOUTHERN PLAINS LATE SUNDAY ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: ECMWF/UKMET COMPROMISE CONFIDENCE: SLIGHTLY ABOVE AVERAGE WHILE THE NON-CANADIAN GUIDANCE AGREES ON THE PROGRESSION OF A SMALL PIECE OF HIGH PRESSURE MOVING IN FROM WESTERN CANADA, THERE IS SIGNIFICANT DISAGREEMENT AT THE SURFACE, WITH THE 12Z GFS MUCH MORE NORTHWESTERLY WITH A FRONT/SURFACE TROUGH ACROSS THE SOUTHERN PLAINS. THE MORE DEPRESSED NON-GFS COMPROMISE FITS THE IDEA OF THE HIGH BEING THE SOURCE OF A SHALLOW COLD AIRMASS. PREFER A COMPROMISE OF THE 00Z ECMWF/12Z UKMET GUIDANCE HERE, WHICH SPLITS THE DIFFERENCES SEEN IN THE NON-GFS GUIDANCE, WITH SLIGHTLY ABOVE AVERAGE CONFIDENCE. SHORTWAVE/FRONT NEAR THE GREAT LAKES LATE SUN ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: ECMWF/UKMET COMPROMISE CONFIDENCE: AVERAGE THIS SYSTEM ALOFT IS EMBEDDED WITHIN A QUICK FLOW REGIME WITHIN THE NORTHERN STREAM OF THE WESTERLIES, WHICH ELIMINATED THE COMPLETE RULING OUT OF THE 12Z NAM/00Z CANADIAN IDEA. WHILE THE 12Z GFS/12Z NAM/00Z ECMWF LOOK SLOWER ALOFT, BEFITTING THE 00Z ECMWF/09Z SREF MEANS, THERE REMAIN PROGRESSION ISSUES AT THE SURFACE IN RELATION TO THIS FEATURE. UNTIL THE REMAINDER OF THE 12Z GUIDANCE SUITE BECOMES AVAILABLE, THE INTERMEDIATE ECMWF/UKMET SOLUTIONS ARE PREFERRED WITH AVERAGE CONFIDENCE. SHORTWAVE CROSSING THE MID-SOUTH/EAST SAT ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: NON-GFS COMPROMISE CONFIDENCE: ABOVE AVERAGE THE 12Z GFS IS STRONGER/SLOWER WITH THIS SHORTWAVE, WHICH IS EMBEDDED WITHIN A ZONAL/QUICK FLOW REGIME. SINCE THIS REGIME FAVORS SHORTWAVES THAT ARE QUICKER AND WITH LESS AMPLITUDE, FAVOR A NON-GFS COMPROMISE WITH ABOVE AVERAGE CONFIDENCE. TROUGH MOVING THROUGH THE NORTHEAST FRI ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GENERAL MODEL COMPROMISE CONFIDENCE: ABOVE AVERAGE THE GUIDANCE SHOWS GOOD AGREEMENT WITH THESE FEATURES. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... ROTH