MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 131 PM EST WED FEB 05 2014 VALID FEB 05/1200 UTC THRU FEB 09/0000 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 12Z MODEL EVALUATION WITH PREFERENCES ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ NAM/GFS INITIALIZATION ERRORS DO NOT SEEM TO DEGRADE THEIR SHORT RANGE FORECASTS. CYCLONES MOVING INTO CA/OR BETWEEN LATE WED AND SAT ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GFS/UKMET/ECMWF COMPROMISE CONFIDENCE: AVERAGE THE FLOW IN WHICH THESE SYSTEMS ARE EMBEDDED WITHIN IS ONE OF LOW AMPLIFICATION WITH BROAD SHORTWAVES. THE GUIDANCE IS AGREEABLE WITH THE FIRST COUPLE LOWS MOVING TOWARDS SOUTHWEST OREGON/NORTHWEST CALIFORNIA. THE 12Z CANADIAN BRINGS A THIRD LOW TOWARDS THE CENTRAL OR COAST SATURDAY AFTERNOON. WHILE THE 00Z GLOBAL ENSEMBLE MEMBERS BRING ANOTHER LOW TOWARDS OREGON, THEY ARE NEARLY A DAY SLOWER. ALL THINGS CONSIDERED, A COMPROMISE OF THE 12Z UKMET/12Z GFS/12Z ECMWF LOOKS BEST IN THIS PROGRESSIVE FLOW REGIME, WITH AVERAGE CONFIDENCE CONSIDERING SYSTEM PROGRESSION. ENERGY IN THE NORTHWEST EJECTING INTO THE PLAINS SAT ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: UKMET/GFS COMPROMISE CONFIDENCE: AVERAGE THE 12Z ECMWF/12Z CANADIAN/12Z NAM ARE STRONGER THAN THE OTHER GUIDANCE WITH THIS SHORTWAVE. THE FLOW IN WHICH THE SYSTEM IS EMBEDDED WITHIN IS ONE OF LOW AMPLIFICATION WITH BROAD SHORTWAVES, ARGUING AGAINST A STRONGER SOLUTION ALOFT. IN ADDITION, THE AVAILABLE ENSEMBLE MEAN SOLUTIONS PREFER A SOLUTION SLOWER THAN THE CANADIAN/ECMWF. A COMPROMISE OF THE 12Z GFS/12Z UKMET IS PREFERRED HERE WITH AVERAGE CONFIDENCE CONSIDERING THE SYSTEM'S PROGRESSIVE NATURE. SHORTWAVE MOVING THROUGH TX FRI/SOUTHEAST SAT LOW FORMING OFFSHORE THE SOUTHEAST SAT ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: CANADIAN/UKMET COMPROMISE CONFIDENCE: AVERAGE DUE TO THE ECMWF'S FASTER-MOVING SYSTEM MOVING INTO THE NORTHERN PLAINS, IT STREAKS THIS SHORTWAVE AND DEVELOPING SURFACE LOW FASTER THAN THE OTHER GUIDANCE, LEADING TO A MORE NORTHEASTERLY SOLUTION OFFSHORE THE SOUTHEAST THAN SEEN IN THE OTHER DETERMINISTIC GUIDANCE. THE 00Z GLOBAL ENSEMBLE LOW PRESSURE CENTER SPREAD SHOWS THE 12Z ECMWF ON THE NORTHEAST FRINGE OF THE GUIDANCE, AND REVEALS THE 00Z ECMWF ENSEMBLE MEAN ITSELF IS BEING STRONGLY WEIGHTED BY SEVEN OF ITS 50 MEMBERS. DUE TO PREFERENCES UPSTREAM, A COMPROMISE OF THE AVAILABLE GUIDANCE, SHOWING A SLOWER TIMING THAN THE ECMWF -- CLOSEST TO 12Z CANADIAN/12Z UKMET -- IS PREFERRED WITH AVERAGE CONFIDENCE CONSIDERING ITS PROGRESSIVE NATURE. SYSTEM/LOW MOVING THROUGH THE NORTHERN MID ATLANTIC/NORTHEAST COAST ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: NON-NAM COMPROMISE CONFIDENCE: ABOVE AVERAGE THE 12Z NAM CONTINUES BEING THE STRONGEST PIECE OF GUIDANCE WITH THIS SYSTEM. AS THE SYSTEM IS SHEARING OUT ALOFT ON THE SOUTHERN FRINGE OF THE POLAR VORTEX LATER TODAY, WILL SIDE THE WITH WEAKER NON-NAM CONSENSUS WITH ABOVE AVERAGE CONFIDENCE CONSIDERING THE NAM'S TRADITIONAL STRONG BIAS WITH SYSTEMS IN THE WESTERLIES. www.wpc.ncep.noaa.gov/html/model2.shtml... ROTH