MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 135 AM EST TUE DEC 02 2014 VALID DEC 02/0000 UTC THRU DEC 05/1200 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 00Z MODEL EVALUATION WITH PREFERENCES ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ NAM/GFS INITIALIZATION ERRORS DO NOT SEEM TO DEGRADE THEIR SHORT RANGE FORECASTS. UPPER TROUGH/CYCLONE MOVING TOWARDS THE WEST COAST FRI ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: NON-GFS COMPROMISE CONFIDENCE: AVERAGE THERE IS A BIT OF UNCERTAINTY WITH THE NEXT PACIFIC SYSTEM APPROACHING THE WEST COAST, WITH THE GFS MORE SOUTHERLY AND THE CANADIAN/UKMET/NAM/ECMWF MORE TO THE NORTH. THE APEX OF THE RIDGE TO ITS NORTH APPEARS TO BE IMPORTANT, AND THE VARIOUS PIECES OF GUIDANCE ARE INTERNALLY CONSISTENT IN KEEPING THE CORE OF THE MID-LEVEL ENERGY ~20 DEGREES SOUTH OF THE RIDGE'S APEX IN NORTHWEST CANADA. THE CONSENSUS HAS STRENGTHENED WITH THE 00Z GUIDANCE, WHICH INCLUDES THE 00Z CANADIAN/00Z UKMET/00Z ECMWF/21Z SREF MEAN. A COMPROMISE OF THE NON-GFS GUIDANCE IS PREFERRED, WITH AVERAGE CONFIDENCE DUE TO THE GROWING CONSENSUS. SYSTEM MOVING THROUGH SOUTH-CENTRAL CANADA THU/FRI ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GFS/ECMWF COMPROMISE CONFIDENCE: AVERAGE THE 00Z ECMWF IS MORE AMPLIFIED WITH THIS SYSTEM THAN THE OTHER GUIDANCE, WHILE THE 00Z UKMET IS THE QUICKEST. THIS SYSTEM IS MOVING UNDER THE BASE OF A VERY BROAD UPPER LEVEL TROUGH, FAVORING A QUICKER/BROADER SOLUTION ALOFT, IMPLYING A SOLUTION WEAKER THAN THE ECMWF. A COMPROMISE OF THE 00Z GFS/00Z ECMWF SHOULD DEAL WITH THE ECMWF'S STRENGTH ISSUE AND THE SPREAD SEEN IN THE GUIDANCE, WHICH IS PREFERRED WITH AVERAGE CONFIDENCE. WEAKENING SYSTEM MOVING NORTH ALONG THE WEST COAST WED/THU ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GFS/ECMWF COMPROMISE CONFIDENCE: SLIGHTLY ABOVE AVERAGE THE 00Z NAM IS ON THE WEAK SIDE OF THE ENVELOPE OF SOLUTIONS WITH THIS SYSTEM WHILE THE 00Z CANADIAN IS ON THE STRONG SIDE, ALLOWING THIS SYSTEM TO IMPACT THE EVOLUTION OF A SEPARATE NORTHERN STREAM SYSTEM MOVING ACROSS SOUTHWEST CANADA. OVERALL, A 00Z GFS/00Z ECMWF COMPROMISE BEST REFLECT THE 12Z ECMWF/00Z GEFS/21Z SREF MEAN SOLUTIONS. SHORTWAVE MOVING THROUGH THE CENTRAL PLAINS THU NIGHT ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: CLOSEST TO THE ECMWF CONFIDENCE: SLIGHTLY ABOVE AVERAGE THE 00Z GFS/00Z CANADIAN ARE SLOW WITH THIS SYSTEM WHILE THE 00Z UKMET IS THE QUICKEST. THIS SYSTEM IS MOVING THROUGH LOW-AMPLITUDE, QUASI-ZONAL FLOW, WHICH ELIMINATES THE GFS/CANADIAN FROM THE START. HOWEVER, THE ECMWF IS SLIGHTLY WEAKER THAN ITS 12Z ENSEMBLE MEAN SOLUTION WHICH APPEARS TO BE CAUSED BY ITS STRONGER SHORTWAVE MOVING ACROSS SOUTHERN CANADA. THE 00Z ECMWF IS CLOSE TO THE 12Z ECMWF/00Z GEFS/21Z SREF MEAN SOLUTIONS, AND IS PREFERRED WITH SLIGHTLY ABOVE AVERAGE CONFIDENCE. SHORTWAVE TROUGH/FRONTS MOVING THROUGH NEW ENGLAND WED/THU ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: NON-NAM COMPROMISE CONFIDENCE: ABOVE AVERAGE THE NON-NAM GUIDANCE SHOWS GREATER PROGRESSION WITH THIS SYSTEM, WHICH BEFITS THE INCREASINGLY ZONAL FLOW PATTERN IN WHICH THE SYSTEM BECOMES EMBEDDED AND PLAYS INTO KNOWN NAM BIASES. A COMPROMISE OF THE 00Z GFS/00Z ECMWF/00Z UKMET/00Z CANADIAN APPEARS BEST HERE WITH ABOVE AVERAGE CONFIDENCE. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... ROTH