MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 259 AM EDT TUE SEP 13 2016 VALID SEP 13/0000 UTC THRU SEP 16/1200 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... ...AN EVALUATION OF THE 00Z MODEL GUIDANCE ALONG WITH FINAL PREFERENCES/FORECAST CONFIDENCE... ...MID-LEVEL CIRCULATION REACHING THE EASTERN FL PENINSULA BY 13/1200Z... FINAL PREFERENCE: A NON-00Z NAM MODEL COMPROMISE FORECAST CONFIDENCE: AVERAGE A DISTURBANCE WHICH HAD BEEN OVER THE BAHAMAS IN RECENT DAYS HAS WORKED ITS WAY JUST OFF THE EASTERN FL COAST. THE NATIONAL HURRICANE CENTER HAS BEEN FOLLOWING THIS SYSTEM FOR DAYS BUT THEIR OUTLOOK ONLY SUGGESTS A 10 PERCENT CHANCE FOR TROPICAL DEVELOPMENT. REGARDLESS...THIS BAND OF VORTICITY COUPLED WITH MOISTURE RICH AIR WILL BRING MODERATE/HEAVY RAINFALL TO THE STATE OF FL. AFTER EVALUATING THE AVAILABLE 00Z GUIDANCE...THE CONSENSUS HAS MOVED NORTHWARD WITH THE BEST MID-LEVEL ENERGETICS MOVING THE COASTAL BORDER OF GA/FL BY 14/0600Z. AS THE 00Z NAM STILL REMAINS EVEN NORTH OF THAT...WILL LEAN TOWARD A NON-00Z MODEL COMPROMISE. ...PERSISTENT TUTT CELL LINGERING OVER THE GULF OF MX... FINAL PREFERENCE: A NON-00Z NAM MODEL COMPROMISE FORECAST CONFIDENCE: SLIGHTLY ABOVE AVERAGE WATER VAPOR IMAGERY DEPICTED A WEAK MID-LEVEL LOW/TUTT CELL SPINNING IN THE VICINITY OF THE CENTRAL GULF COAST. THE GUIDANCE GENERALLY WEAKEN THIS FEATURE IN TIME EXCEPT FOR THE 00Z NAM WHICH FORMS A RATHER IMPRESSIVE UPPER LOW OVER THE CENTRAL GULF OF MX. WHILE PERSISTENT IN CREATING IT...THIS ALSO APPEARS UNREASONABLE SO WILL RELY ON OTHER AVAILABLE SOLUTIONS. ...LONGWAVE TROUGH SKIRTING THE CANADIAN INTERNATIONAL BORDER THROUGH WEDNESDAY... ...CORRESPONDING COLD FRONT... FINAL PREFERENCE: BLEND OF THE 00Z GFS/GEFS MEAN WITH THE 00Z ECMWF FORECAST CONFIDENCE: SLIGHTLY BELOW AVERAGE SPLIT FLOW ACROSS THE CONUS WILL BE APPARENT AS PROGRESSIVE FLOW SETTLES OVER THE NORTHERN TIER OF THE COUNTRY WHILE A POSITIVELY-TILTED TROUGH SINKS DOWN TOWARD THE DESERT SOUTHWEST. THE LONGWAVE TROUGH ACCELERATING ALONG THE INTERNATIONAL BORDER WITH CANADA IS CURRENTLY OVER SOUTHERN MANITOBA WITH THE ATTENDANT COLD FRONT STRETCHING FROM THE UPPER GREAT LAKES DOWN INTO THE TX/OK PANHANDLES. THIS UPPER TROUGH AND THE ACCOMPANYING WEAK IMPULSES TO THE SOUTH WILL ALL TRANSLATE EASTWARD IN TIME WITH SOME TIMING DIFFERENCES EVIDENT. THERE HAS BEEN A NOTABLE SHIFT IN THE GUIDANCE THE FASTER SIDE...PARTICULARLY THE 00Z CMC WHICH HAD BEEN SLOWER DURING ITS PAST RUN. WILL NUDGE THE PREFERENCE TOWARD SOMETHING FARTHER EAST TO ACCOMMODATE THESE RECENT TRENDS. THE PREFERENCE WILL BE A BLEND OF THE 00Z GFS/GEFS MEAN BUT INCORPORATING THE 00Z ECMWF WHICH IS A BIT SLOWER IN CASE THE NEXT MODEL CYCLE TRENDS SLOWER. ...CLOSED LOW INITIALLY OVER THE SOUTHWESTERN U.S... ...SLOW-MOVING LONGWAVE TROUGH REACHING THE NORTHERN PLAINS/UPPER MIDWEST BY 16/1200Z... FINAL PREFERENCE: BLEND OF THE 00Z GFS/ECMWF FORECAST CONFIDENCE: SLIGHTLY ABOVE AVERAGE AN INSIDE SLIDER CURRENTLY SINKING SOUTHWARD FROM THE CENTRAL GREAT BASIN TOWARD THE SOUTHWESTERN U.S. WILL GRADUALLY DEVELOP A CLOSED CENTER ACROSS THE SIERRA NEVADA RANGE BEFORE ACCELERATING EASTWARD. THROUGH 15/0000Z...ENSEMBLE SPAGHETTI PLOTS SHOW A LOW AMOUNT OF SPREAD WITH THIS SYSTEM AS IT OPENS UP WHILE MOVING SLOWLY TOWARD THE ROCKIES/HIGH PLAINS REGION. EVEN BY 16/1200Z...ENSEMBLE LOW PLOTS GENERALLY ARE CONSISTENT WITH A SURFACE CYCLONE SOMEWHERE OVER THE UPPER MIDWEST. ONLY THE 00Z NAM DIVERGES FROM THIS SOLUTION BEING OFF TO THE WEST ACROSS THE DAKOTAS. UTILIZING A BLEND OF THE 00Z GFS/ECMWF APPEARS REASONABLE GIVEN THE LOW AMOUNT OF SPREAD EVIDENT. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... RUBIN-OSTER