MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 317 PM EDT THU SEP 18 2014 VALID SEP 18/1200 UTC THRU SEP 22/0000 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... ============================================== 12Z MODEL EVALUATION AND PREFERENCES ============================================== NAM/GFS INITIALIZATION ERRORS DO NOT APPEAR TO SIGNIFICANTLY AFFECT THEIR LARGE SCALE OUTPUT. ============================================== ...REMNANTS OF ODILE... PREFERENCE: BLEND OF 12Z NAM/GFS/ECMWF/UKMET CONFIDENCE: SLIGHTLY ABOVE AVERAGE THE 12Z CANADIAN STRAYS FAR FROM CONSENSUS WITH RESPECT TO QPF. THE NAM/GFS/ECMWF APPEAR CONSISTENT WITH ONE ANOTHER. VIEWING THE FULL 12Z SUITE...THE UKMET WAS SIMILAR ENOUGH IN THE MID LEVEL MASS FIELDS AND IN QPF...TO INCLUDE IN OUR PREFERENCE. ...DEEP UPPER TROUGH/CLOSED LOW AFFECTING THE WESTERN STATES THROUGH SAT... PREFERENCE: BLEND OF THE 12Z GFS/ECMWF/UKMET/CANADIAN CONFIDENCE: ABOVE AVERAGE FEW MODEL DIFFERENCES EXIST HERE. THE MOST NOTICEABLE EXCEPTION IS THE 12Z NAM...WHICH IS MUCH SLOWER TO BRING A SHORTWAVE AROUND THE BASE OF THE LOW AND SWING THE LARGER SCALE LOW INTO A NEGATIVE TILT AROUND 21/00Z. THE GLOBAL MODELS...HOWEVER...SHOW STRONG AGREEMENT. ...UPPER TROUGH DIGGING INTO THE EASTERN U.S THIS WEEKEND... ...SURFACE LOW DEVELOPING OFF THE SOUTHEAST UNITED STATES COAST FRI/SAT... PREFERENCE: BLEND OF 12Z GEFS MEAN WITH 12Z ECMWF CONFIDENCE: AVERAGE A NUMBER OF PIECES OF GUIDANCE...ESPECIALLY THE GFS AND UKMET...HAVE TRENDED FASTER WITH A NORTHERN STREAM TROUGH DIGGING INTO THE MIDWEST/GREAT LAKES. THE 12Z GFS MAY DO SO A LITTLE TOO AGGRESSIVELY...AND ITS SURFACE LOW POSITION OVER SOUTHERN QUEBEC AT 22/00Z HAS RELATIVELY LITTLE SUPPORT. IT APPEARS THE 12Z GEFS MEAN DOES A GOOD JOB OF DISPLAYING THE TREND WHILE DEPICTING A BETTER SUPPORTED SURFACE PATTERN...BOTH IN QUEBEC AND OFF THE SOUTHERN ATLANTIC COAST. THE ECMWF TRENDED SLOWER OFF THE ATLANTIC COAST...BUT WE ARE STILL COMFORTABLE BLENDING THE GEFS MEAN WITH THE 12Z ECMWF TO REPRESENT WPC CONTINUITY WITH A NUDGE TOWARD TRENDS. ...LEAD SHORTWAVE INTO THE PACIFIC NORTHWEST THIS WEEKEND... PREFERENCE: BLEND OF THE OPERATIONAL MODELS CONFIDENCE: ABOVE AVERAGE A DEEP LONGWAVE TROUGH OFFSHORE SHOULD HAVE LITTLE IMPACT THROUGH SUNDAY...BUT MODELS DO BRUSH THE PACIFIC NW COAST WITH LOW PRESSURE ASSOCIATED WITH A LEAD SHORTWAVE THIS WEEKEND. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... BURKE