MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1259 AM EDT FRI SEP 16 2016 VALID SEP 16/0000 UTC THRU SEP 19/1200 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 00Z NAM/GFS EVALUATION INCLUDING PRELIMINARY PREFERENCES ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ LOW PRESSURE OVER THE DAKOTAS/MINNESOTA TODAY WITH TRAILING COLD FRONT INTO THE SRN PLAINS ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 00Z GFS / 12Z ECMWF BLEND CONFIDENCE: AVERAGE THE GFS/ECMWF ARE CLOSEST TO THE LATEST ENSEMBLE MEANS REGARDING THE UPPER TROUGH...SURFACE LOW AND FRONTAL POSITIONS THROUGH 12Z/19. THE 12Z UKMET IS FLATTER WHILE THE 12Z CMC IS STRONGER THAN THE CONSENSUS. TROPICAL CYCLONE JULIA ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 12Z ECMWF CLOSEST TO NHC TRACK CONFIDENCE: REFER TO NHC JULIA HAS BEEN HOVERING BETWEEN A TROPICAL STORM AND TROPICAL DEPRESSION OVER THE PAST 24 HOURS AND WHILE THE 03Z NHC ADVISORY LISTED JULIA AS A TROPICAL STORM...IT IS FORECAST TO GO BACK TO DEPRESSION STATUS LATER TODAY. WHILE NO MODEL MATCHES THE NHC TRACK FOR ALL FORECAST HOURS THROUGH 12Z/19...THE 12Z ECMWF IS PROBABLY THE CLOSEST MATCH. MID-UPPER LEVEL LOW OFF OF THE SOUTHWESTERN U.S. COAST THIS WEEKEND ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GENERAL MODEL COMPROMISE CONFIDENCE: SLIGHTLY ABOVE AVERAGE THE MODELS SHOW SIMILARLY WITH THIS SYSTEM. FIRST UPPER TROUGH AXIS AND COLD FRONT ENTERING THE NORTHWEST SAT ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 00Z GFS...12Z ECMWF...12Z UKMET BLEND CONFIDENCE: SLIGHTLY BELOW AVERAGE WITH A FAST ZONAL FLOW UPSTREAM...AND MINOR AMPLITUDE/TIMING SPREAD IN THE LATEST ENSEMBLES...CONFIDENCE IS A BIT BELOW AVERAGE OVERALL...AND MUCH BELOW AVERAGE WITH THE TIMING OF INDIVIDUAL VORTICITY MAXIMA WITHIN THE LARGER SCALE TROUGH. CONSIDERING THE LATEST ENSEMBLE AND DETERMINISTIC CLUSTERING...THE 00Z GFS...12Z ECMWF AND 12Z UKMET ARE CLOSEST TO THE MIDDLE. SECOND UPPER TROUGH AXIS NEAR THE PACIFIC NORTHWEST MON MORNING ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 12Z ECMWF MEAN OR 00Z GFS / 12Z ECMWF BLEND CONFIDENCE: BELOW AVERAGE SIMILAR TO THE PREVIOUS SYSTEM...FAST ZONAL FLOW LEAVES ROOM FOR ADJUSTMENTS WITH FUTURE MODEL RUNS...EVIDENCED BY POOR RUN TO RUN CONTINUITY. HOWEVER...THE LATEST ENSEMBLE DATA FROM THE 12Z/15 CYCLE SHOWED SOME CONVERGENCE OFFSHORE OF THE PACIFIC NORTHWEST WITH THE 500 MB FLOW. THE 12Z ECMWF MEAN IS DOWN THE MIDDLE OF THE ECMWF/GEFS/CMC MEMBERS...WITH IS BEST REPRESENTED BY A MORE AMPLIFIED 00Z GFS AND FLATTER 12Z ECMWF THROUGH 12Z/18. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... OTTO