MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1241 AM EDT WED OCT 29 2014 VALID OCT 29/0000 UTC THRU NOV 01/1200 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 00Z NAM/GFS EVALUATION WITH PRELIMINARY MODEL PREFERENCES ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ NAM/GFS INITIALIZATION ERRORS DO NOT SEEM TO DEGRADE THEIR SHORT RANGE FORECASTS. AMPLIFIED TROUGH APPROACHING WESTERN NORTH AMERICA ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: CLOSE TO THE 00Z GFS CONFIDENCE: ABOVE AVERAGE THE 00Z NAM IS SLOW WITH THIS SYSTEM -- ITS USUAL BIAS -- WHILE THE 12Z UKMET IS QUICK WITH THIS SYSTEM -- ITS USUAL BIAS. THE 00Z GFS LIES IN THE MIDDLE OF THE GUIDANCE SPREAD AND IS CLOSE TO THE 12Z ECMWF/18Z GEFS ENSEMBLE MEANS. TROUGH AMPLIFYING ACROSS EASTERN NORTH AMERICA CLOSED LOW POTENTIALLY DROPPING INTO THE CAROLINAS ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: SREF MEAN/ECMWF/GFS/GEFS MEAN COMPROMISE CONFIDENCE: BELOW AVERAGE TRENDS WITH THIS SYSTEM ARE MORE AMPLIFIED DUE TO THE AMPLIFYING RIDGE ACROSS THE PLAINS AND AMPLIFYING TROUGH NEAR THE WEST COAST. THE 00Z NAM IS THE FARTHEST SOUTHWEST BY SATURDAY MORNING -- ITS USUAL BIAS -- WHILE THE 12Z UKMET IS THE FARTHEST NORTHEAST, NEAR THE 12Z ECMWF ENSEMBLE MEAN SOLUTION. THE 18Z GEFS MEAN/00Z GFS/12Z ECMWF/21Z SREF MEAN ARE IN RELATIVELY GOOD AGREEMENT WITH THEIR FORECASTS. THE MAIN PROBLEM IS HOW ANOMALOUS THIS PATTERN BECOMES BY SATURDAY MORNING. THE 12Z ECMWF SHOWS 500 HPA HEIGHT ANOMALIES OF 5.5 SIGMAS BELOW AVERAGE, WHICH IS ROUGHLY A ONCE IN A 50 YEAR EVENT. THE ST. LOUIS UNIVERSITY CIPS ANALOGS INDICATE THAT THE OCT 26 1990 (BONNER BRIDGE STORM), DEC 6 2003, DEC 6 1985, DEC 4 1987, NOV 6 2010, AND NOV 18 2008 PATTERNS ARE THE CLOSEST MATCHES ALOFT TO WHAT IS FORECAST. WITH A FORECAST THIS EXTREME, CONFIDENCE IN ANY OF THE GUIDANCE/MODEL CHOICE IS BELOW AVERAGE. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... ROTH