MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 302 AM EDT SUN SEP 11 2016 VALID SEP 11/0000 UTC THRU SEP 14/1200 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... ...SHARP BAND OF HEIGHT FALLS LIFTING THROUGH THE INTERIOR NORTHEAST SUNDAY MORNING... ...ACCOMPANYING DEEP SURFACE CYCLONE/COLD FRONT... FINAL PREFERENCE: A NON-00Z NAM MODEL CONSENSUS FORECAST CONFIDENCE: ABOVE AVERAGE WATER VAPOR IMAGERY SHOWED A SHORTWAVE TROUGH ACCELERATING THROUGH THE GREAT LAKES/OH VALLEY REGION WITH A DEEPENING SURFACE LOW TRACKING ALONG THE ONTARIO/QUEBEC BORDER. WHILE MODEL SOLUTIONS AGREE ON THE UPPER TROUGH POSITION...THE 00Z NAM APPEARS TO BE A TAD SLOWER WITH THE FRONTAL PROGRESSION OFF THE EASTERN SEABOARD. A NON-00Z NAM MODEL CONSENSUS APPEARS REASONABLE HERE. ...VORTICITY CENTERS APPROACHING THE EASTERN FL PENINSULA FROM THE BAHAMAS REGION... FINAL PREFERENCE: BLEND OF THE 00Z GFS/ECMWF FORECAST CONFIDENCE: AVERAGE THE NATIONAL HURRICANE CENTER CONTINUES TO MONITOR AN AREA OF DISTURBED WEATHER JUST EAST OF THE BAHAMAS. HOWEVER...THEIR LATEST TROPICAL OUTLOOK ONLY SUGGESTS A 10 PERCENT CHANCE OF DEVELOPMENT DURING THE NEXT 48 HOURS. REGARDLESS...MODELS SHOW AN AXIS OF MID-LEVEL VORTICITY TRACKING WESTWARD REACHING THE EASTERN FL PENINSULA BY 13/0600Z. THERE ARE SOME RATHER ROBUST SOLUTIONS INCLUDING THE 00Z NAM/CMC/UKMET. WILL STICK WITH A MORE CONSERVATIVE APPROACH FAVORING A COMBINATION OF THE 00Z GFS/ECMWF. ...PERSISTENT TUTT CELL MEANDERING ABOUT THE WESTERN/CENTRAL GULF COASTS. FINAL PREFERENCE: NON-00Z NAM MODEL COMPROMISE FORECAST CONFIDENCE: SLIGHTLY ABOVE AVERAGE A WEAK TUTT CELL REMAINS ALONG THE UPPER TX COAST WITH THIS FEATURE GENERALLY MEANDERING ABOUT THE GULF COAST THE NEXT COUPLE OF DAYS. IT APPEARS THIS CIRCULATION WILL DRIFT EASTWARD DURING THE NEXT 24 HOURS BEFORE NOSING SOUTHWARD AGAIN. THE MOST EXTREME SOLUTION IS THE 00Z NAM WITH AN EXPANSIVE UPPER LOW SPINNING OVER THE CENTRAL GULF OF MX FROM MONDAY ONWARD. WILL REJECT THIS FORECAST AND FAVOR A NON-00Z MODEL COMPROMISE. ...INITIAL WEAK HEIGHT FALLS TRACKING ALONG THE NORTHERN TIER STATES ON MONDAY... ...REINFORCING SHORTWAVE ENERGY CROSSING THE GREAT LAKES BY MID-WEEK... ...ATTENDANT COLD FRONT... FINAL PREFERENCE: BLEND OF THE 00Z ECMWF/UKMET WITH THE 12Z ECMWF/UKMET FORECAST CONFIDENCE: SLIGHTLY BELOW AVERAGE PERSISTENT UPPER TROUGHING WILL HELP DRAW ANOTHER SYSTEM OR TWO INTO THE PICTURE DURING THE NEXT FEW DAYS. THE INITIAL POSITIVELY-TILTED TROUGH CURRENTLY OVER BRITISH COLUMBIA/ALBERTA WILL DRIVE SOUTH AND EAST SPREADING WEAK HEIGHT FALLS ACROSS THE NORTHERN TIER OF THE COUNTRY. THE 00Z GFS SEEMS TO BE ON THE QUICKER SIDE OF THE SPREAD WITH A BIT MORE ENSEMBLE SUPPORT FOR THE 00Z/12Z ECMWF/UKMET. THEREAFTER...ADDITIONAL SHORTWAVE ENERGY SURGES DOWN FROM CENTRAL CANADA REACHING THE UPPER MIDWEST/GREAT LAKES BY LATE TUESDAY/EARLY WEDNESDAY. THIS LEADS TO FURTHER SPREAD IN THE GUIDANCE WITH SOME RUN-TO-RUN DIFFERENCES WHEN COMPARING THE LATEST 00Z MODEL SUITE TO THE PREVIOUS CYCLE. MOST NOTABLY...THE 00Z ECMWF/UKMET TRENDED QUICKER ON DAY 3 WITH THE NEXT SHORTWAVE RACING THROUGH THE GREAT LAKES. FEEL THERE WILL CONTINUE TO BE WAFFLING BETWEEN MODEL RUNS SO PLAN ON AVERAGING THE TWO AT THIS POINT. ...QUASI-STATIONARY UPPER LOW LINGERING OFF THE SOUTHERN CA COAST EARLY ON... ...EXPANSIVE CLOSED LOW SPLITTING OFF OVER THE SOUTHWESTERN STATES EARLY/MID-NEXT WEEK... FINAL PREFERENCE: A NON-00Z/12Z UKMET MODEL COMPROMISE FORECAST CONFIDENCE: ABOVE AVERAGE A PERSISTENT CIRCULATION LOOMS OFF THE COAST OF SOUTHERN CA WITH THE ONLY NOTABLE SENSIBLE WEATHER IMPACT IS PERHAPS AN INCREASE IN CLOUD COVER NORTHEAST OF THIS FEATURE. IN ADVANCE OF A STRONG BAND OF HEIGHT FALLS DROPPING DOWN FROM THE PACIFIC NORTHWEST...THIS CLOSED LOW EVENTUALLY OPENS UP AND WEAKENS WHILE MOVING INTO SOUTHERN UT BY 13/0000Z. THEN THE ATTENTION TURNS TO THE UPPER TROUGH SLIDING DOWN THE INTERIOR WEST WITH AN EVENTUAL TRANSITION TO A BROAD UPPER LOW ENCOMPASSING MUCH OF THE SOUTHWESTERN STATES. BY 14/0000Z...THE 00Z/12Z UKMET ARE DISPLACED EAST OF THE STRONGER CONSENSUS. THEY SEEM TO REMAIN THE MOST OUTLYING SOLUTIONS SO WILL ELIMINATE THEM FROM CONSIDERATION AT THIS TIME AND FAVOR THE BETTER CLUSTERING. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... RUBIN-OSTER