MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1258 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 NAM/GFS ALONG WITH PRELIMINARY PREFERENCES/FORECAST CONFIDENCE... ...MID-LEVEL CIRCULATION REACHING THE EASTERN FL PENINSULA BY 13/1200Z... PRELIMINARY PREFERENCE: BLEND OF THE 12Z ECMWF/ECMWF ENSEMBLE MEAN 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. DESPITE THIS BEING A SHORT-TERM FORECAST...THERE ACTUALLY ARE SOME NORTH/SOUTH DIFFERENCES WITH WHERE THE BEST MID-LEVEL ENERGETICS ARE LOCATED. AS HAS BEEN ITS THEME...THE 00Z NAM IS WELL TO THE NORTH WITH THE 00Z GFS SOMEWHAT JOINING IT. MOST OTHER SOLUTIONS CLUSTER TO THE SOUTH WHICH IS WHERE A MAJORITY OF THE NON-NAM FORECASTS HAD BEEN RESIDING IN RECENT DAYS. PLAN ON STICKING WITH THIS SOUTHERN SOLUTION ALTHOUGH WILL NOT INCORPORATE THE 12Z UKMET GIVEN ITS CONTINUED MORE ROBUST NATURE. A COMBINATION OF THE 12Z ECMWF/ECMWF ENSEMBLE MEAN IS RECOMMENDED HERE. ...PERSISTENT TUTT CELL LINGERING OVER THE GULF OF MX... PRELIMINARY 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... PRELIMINARY PREFERENCE: BLEND OF THE 18Z GEFS/21Z SREF MEANS 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. BY 15/0000Z...THE 00Z NAM AND 12Z ECMWF/CMC ARE SLOWER AS SUPPORTED BY THE 12Z ECMWF ENSEMBLE MEAN. ON THE FASTER SIDE ARE THE 00Z GFS/12Z UKMET WITH THE 18Z GEFS/21Z SREF MEANS SANDWICHED IN THE MIDDLE SOMEWHERE. INTERESTINGLY...THERE ARE STILL PLENTY OF SLOWER GEFS MEMBERS AS NOTED ON THE 570-DM SPAGHETTI PLOT. FOR NOW...WILL BLEND THE 18Z GEFS/21Z SREF MEAN SOLUTIONS. ...CLOSED LOW INITIALLY OVER THE SOUTHWESTERN U.S... ...SLOW-MOVING LONGWAVE TROUGH REACHING THE NORTHERN PLAINS/UPPER MIDWEST BY 16/1200Z... PRELIMINARY PREFERENCE: BLEND OF THE 00Z GFS/12Z 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 MOVES SLOWLY TOWARD THE ROCKIES/HIGH PLAINS REGION. EVENTUALLY THE 12Z UKMET BECOMES A BIT SLOWER THAN THE CONSENSUS. EVEN BY 16/1200Z...ENSEMBLE LOW PLOTS GENERALLY ARE CONSISTENT WITH A SURFACE CYCLONE SOMEWHERE OVER THE UPPER MIDWEST. UTILIZING A BLEND OF THE 00Z GFS/12Z 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