MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1203 AM EST WED NOV 23 2016 VALID NOV 23/0000 UTC THRU NOV 26/1200 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 00Z NAM/GFS EVALUATION INCLUDING PRELIMINARY MODEL PREFERENCES ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ LOW PRESSURE DEPARTING FROM NEW ENGLAND TODAY ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GENERAL MODEL BLEND CONFIDENCE: ABOVE AVERAGE ONLY MINOR DIFFERENCES EXIST WITH THE LATEST GUIDANCE SUCH THAT A GENERAL MODEL BLEND IS PREFERRED TO SMOOTH OUT SMALLER SCALE DIFFERENCES. SHORTWAVE TROUGH CROSSING THE MISSISSIPPI VALLEY TODAY WITH THE ACCOMPANYING SURFACE LOW MOVING TOWARD THE GREAT LAKES TONIGHT ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 12Z ECMWF/00Z NAM BLEND CONFIDENCE: ABOVE AVERAGE THE 00Z GFS STILL APPEARS A TAD FAST WITH THE LEADING EDGE OF THE UPPER TROUGH NEARING THE EAST COAST THU MORNING. THE NAM/ECMWF SHOW BETTER AGREEMENT TO EACH OTHER AND THE ENSEMBLE MEANS. UPPER TROUGH REACHING THE CENTRAL PLAINS THU AND BROADENING OVER THE GREAT LAKES BY LATE FRIDAY ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 70% 12Z ECMWF / 30% 00Z NAM CONFIDENCE: AVERAGE THE 00Z GFS AND EVEN THE 00Z NAM ARE TOWARD THE SLOWER/DEEPER SIDE WITH THE UPPER TROUGH AS IT REACHES THE CNTRL PLAINS ON THU. THE ECMWF/UKMET AND MANY OF THE ENSEMBLES HAVE TRENDED FLATTER/FASTER WITH THIS FEATURE COMPARED TO YESTERDAY. WHILE A MIDDLE GROUND IS LIKELY BEST HERE...PROBLEMS ARISE IN THE 00Z GFS DOWNSTREAM ACROSS THE GREAT LAKES AND NORTHEAST WITH A LIKELY MISHANDLING OF A VORT MAX DROPPING DOWN FROM THE UPPER MISSISSIPPI VALLEY. THE 00Z GFS TRENDED SLOWER WITH THIS FEATURE DURING THE DAY ON FRI WHICH IMPACTS ITS TIMING TOWARD THE EAST COAST FRI NIGHT. THE 00Z GFS STANDS OUT AS AN OUTLIER HERE FROM THE REMAINING MODELS AND ITS PREVIOUS RUNS...WITH THE 00Z NAM AND 12Z ECMWF LOOKING BETTER IN TERMS OF SHAPE AND POSITION OF THE UPPER TROUGH. MORE WEIGHT IS PREFERRED TO THE 12Z ECMWF AS THE 00Z NAM APPEARS A BIT TOO STRONG ALOFT WITH LITTLE ENSEMBLE SUPPORT FOR THE NAM STRENGTH. AMPLIFYING TROF OFF THE WEST COAST FRIDAY (INCLUDING LEAD S/W & SFC LOW CLIPPING NW ON THURS NIGHT/FRIDAY MORNING) ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 12Z ECMWF...12Z EC MEAN CONFIDENCE: BELOW AVERAGE COMPLEX SETUP AND COMPLICATED INTERACTIONS WITH NUMEROUS VORTICITY MAXIMA MAKE FOR A CHALLENGING FORECAST. THE 00Z GFS IS AN OUTLIER OF THE DETERMINISTIC GUIDANCE WITH ITS HANDLING OF A VORT MAX WITHIN THE CLOSED LOW THAT DEVELOPS WEST OF BRITISH COLUMBIA...WITH THE LATEST ENSEMBLES SUPPORTING THE POSITION OF A NON-GFS COMPROMISE HERE. HOWEVER...LATER IN THE FORECAST...THE GFS HAS HELD THE BEST RUN TO RUN CONTINUITY WITH THE TIMING OF THE UPPER TROUGH OFF OF THE WEST COAST FRI INTO SAT AND THE ECMWF HAS BEEN TRENDING SLOWER TOWARD THE GFS. THE ECMWF APPEARS A BIT FAST WITH A PIECE OF THIS TROUGH...OR WITH SHORTWAVE ENERGY ENTERING THE WEST COAST FRI NIGHT...BUT THE ECMWF SEEMS OKAY WITH TIMING OF THE UPSTREAM TROUGH AXIS. GIVEN THE COMPLEXITY AND AGREEMENT OF THE LATEST ENSEMBLE MEANS...WILL WEIGHT THE PREFERENCE TOWARD THE MEANS...WITH THE 12Z ECMWF LIKELY THE CLOSEST DETERMINISTIC MODEL OF THE GROUP. SOUTHERN STREAM JET ENERGY ACROSS THE SRN U.S. AND MOISTURE RETURN INTO TEXAS FOR FRI/SAT ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 12Z UKMET/12Z EC MEAN BLEND CONFIDENCE: BELOW AVERAGE ENSEMBLE SPAGHETTI HEIGHT CONTOURS SHOW A FAR DEGREE OF SPREAD WITH SMALL PERTURBATIONS CONTAINED WITHIN THE SRN STREAM JET AXIS AIMED FROM NRN BAJA INTO TEXAS ON FRI. THE 12Z ECMWF HAS A STRONGER WAVE WITHIN THE JET AXIS OVER TEXAS BY SAT MORNING...ALLOWING FOR A WEAKER 850 MB RIDGE OVER THE LONE STAR STATE AND GREATER MOISTURE RETURN INTO THE REGION. THE ECMWF IS ON THE MORE AGGRESSIVE SIDE OF THE LATEST DETERMINISTIC MODELS WITH THIS SCENARIO...AND WOULD PREFER TO BE LESS EXTREME THAN THE 12Z ECMWF. DESPITE ITS LIKELY ISSUES UPSTREAM...THE 12Z UKMET IS AN OKAY MIDDLE GROUND MODEL ACROSS TEXAS ALONG WITH THE DAMPENED 12Z ECMWF MEAN. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... OTTO