MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 101 AM EDT THU APR 06 2017 VALID APR 06/0000 UTC THRU APR 09/1200 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 00Z NAM/GFS EVALUATION WITH PRELIMINARY PREFERENCES ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 00Z NAM/GFS ANALYSES OF PRECIPITABLE WATER VALUES APPEAR REASONABLE GIVEN THE LATEST OBSERVATIONS FROM 00Z RAOB DATA ACROSS THE LOWER 48...LIKELY RESOLVING ANY ISSUES SEEN WITH THE 12Z NAM FROM WEDNESDAY. DEEP CYCLONE MOVING INTO THE NORTHEAST LATE THURSDAY ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GENERAL MODEL COMPROMISE CONFIDENCE: AVERAGE ALL THE GUIDANCE HANDLES THE MASS FIELDS OF THIS STRONG SYSTEM RATHER SIMILARLY WITH ONLY SMALL DIFFERENCES WITH STRENGTH/POSITION/SHAPE OF THE UPPER TROUGH. A GENERAL MODEL COMPROMISE IS RECOMMENDED TO SMOOTH OUT SMALLER SCALE DIFFERENCES. ...SURFACE LOW MOVING JUST OFFSHORE THE NORTHWEST EARLY THIS MORNING... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: NON 12Z CMC BLEND CONFIDENCE: SLIGHTLY ABOVE AVERAGE ENSEMBLE SCATTER LOW PLOT TRENDS HAVE BEEN FASTER OVER THE PAST 3 CYCLES...WITH A DECENT CONSENSUS SHOWN IN THE LATEST CYCLE AGREEING WITH THE 00Z NAM/GFS AND THE 12Z ECMWF/UKMET. HOWEVER...THE 12Z CMC STANDS OUT AS SLOWER AND DEEPER THAN THE REMAINING CONSENSUS AND SLOWER WITH RESPECT TO THE ENSEMBLES. GIVEN THE CMC TENDS TO BE A LESS RELIABLE MODEL REGARDING MASS FIELDS...AND ITS LACK OF SUPPORT AND THE SHORT TERM NATURE OF THIS FORECAST...A NON 12Z CMC BLEND IS PREFERRED. ...DEEP CYCLONE MOVING OFFSHORE OF THE NORTHWEST FRIDAY WITH SURFACE LOW MOVING NEAR U.S./CANADIAN BORDER FRIDAY/SATURDAY... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: NON 12Z CMC BLEND CONFIDENCE: AVERAGE ONLY THE 12Z CMC SHOWS SIGNIFICANTLY DIFFERENT WITH THIS SYSTEM WITH A SLOWER 500 MB/SURFACE TRACK TOWARD THE PACIFIC NORTHWEST. BETTER ENSEMBLE AND REMAINING DETERMINISTIC SUPPORT EXISTS FOR A NON 12Z CMC MODEL BLEND. ...SYSTEM MOVING INTO CALIFORNIA FRIDAY NIGHT... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 00Z NAM CONFIDENCE: BELOW AVERAGE ENSEMBLE SPAGHETTI HEIGHTS SHOW A GREAT DEAL OF SPREAD LOWERING CONFIDENCE. HOWEVER...THERE IS ENOUGH AGREEMENT IN THE ENSEMBLES TO STRAY AWAY FROM THE 12Z ECMWF WHICH APPEARS TO BE ON THE FAR SRN EDGE OF THE GUIDANCE WITH RESPECT TO THE 500 MB TROUGH AS IT ENTERS THE WEST COAST EARLY SAT. THE 12Z ECMWF MEAN HEDGES A BIT WEAKER WITH THE TROUGH...TOWARD THE REMAINING MODEL CONSENSUS. THE 12Z UKMET IS ON THE OTHER SIDE OF THE SPECTRUM WITH A MUCH FLATTER TROUGH. THE 00Z NAM ACTUALLY APPEARS TO BE A DECENT MIDDLE GROUND AND NOT ON THE EDGES OF THE ENSEMBLE GUIDANCE WHICH IS WHERE THE PREFERENCE WILL LEAN FOR NOW. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... OTTO