MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1233 PM EDT MON SEP 19 2016 VALID SEP 19/1200 UTC THRU SEP 23/0000 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 12Z MODEL EVALUATION...INCLUDING THE NAM AND GFS ...SHORTWAVE OVER TN/MS/AL THIS MORNING... ...CLOSED LOW DEVELOPMENT OVER THE SOUTHEAST... ...POST-TROPICAL REMNANTS OF JULIA NEAR SOUTHEAST NC... PREFERENCE: BLEND OF THE 06Z GEFS MEAN AND 00Z ECENS MEAN CONFIDENCE: SLIGHTLY BELOW AVERAGE A SHORTWAVE TROUGH MOVING TOWARD THE SOUTHERN APPALACHIANS WILL AMPLIFY AND CLOSE OFF OVER THE SOUTHEAST OVER THE NEXT COUPLE OF DAYS...AND IN THE PROCESS WILL BE ABSORBING THE REMNANTS OF POST-TROPICAL CYCLONE JULIA EAST OF THE CAROLINAS. THE GUIDANCE SUPPORTS A WEAK FRONTAL ZONE ACROSS THE MID-ATLANTIC COASTAL PLAIN ALONG WITH A WEAK AREA OF LOW PRESSURE FOCUSED NEAR THE COAST THROUGH THE PERIOD. THE 12Z NAM TENDS TO BE A BIT STRONGER WITH THE HEIGHT FALLS AND ALSO WANTS TO RETROGRADE THE UPPER LOW BACK TO THE WEST MORE THAN ANY OTHER MODEL TOWARD THE END OF THE PERIOD. THE 00Z ECMWF ALSO RETROGRADES THE SYSTEM A BIT MORE TO THE WEST...AT LEAST RELATIVE TO THE 12Z GFS/00Z UKMET AND 00Z CMC. THE 06Z GEFS MEAN AND 00Z ECENS MEAN BOTH CLUSTER TOWARD ESSENTIALLY THE MODEL CONSENSUS...AND WILL PREFER A BLEND OF THESE SOLUTIONS FOR NOW. ...HURRICANE PAINE SOUTHWEST OF BAJA CALIFORNIA... PREFERENCE: PLEASE CONSULT THE LATEST NHC FORECAST ADVISORY THE 12Z NAM/00Z CMC AND 00Z ECMWF ARE ALL GENERALLY A LITTLE SLOWER AND LEFT OF THE NHC TRACK OF HURRICANE PAINE. THE 12Z GFS IS CLOSEST TO THE NHC FORECAST...AND OFFICIALLY THE FORECAST CALLS FOR PAINE TO BECOME A REMNANT LOW BY 48 HOURS AS IT APPROACHES THE NORTHERN PORTIONS OF THE BAJA PENINSULA. AS THE SYSTEM WEAKENS...IT IS EXPECTED THAT MID AND HIGH LEVEL MOISTURE WILL SHEAR OFF TO THE NORTHEAST AND ADVANCE INTO THE SOUTHWEST U.S. WHICH WILL INCREASE THE POTENTIAL FOR SOME LOCALLY HEAVY RAINS. PLEASE CONSULT THE LATEST NHC FORECAST ADVISORY FOR MORE DETAILS ON PAINE. ...MID-UPPER LEVEL LOW SOUTHWEST OF CA... ...TRACKING INTO THE SOUTHWEST TUES... ...ENERGY REACHING THE CENTRAL PLAINS WED... PREFERENCE: 00Z GFS/ECMWF BLEND CONFIDENCE: SLIGHTLY ABOVE AVERAGE THE BIGGEST DIFFERENCES COME WITH THE LEAD VORT ENERGY TRACKING NORTH THROUGH THE GULF OF CA AND THEN SHEARING NORTHEAST AHEAD OF THE REMAINS OF THE WEAKENING UPPER LOW PRESENTLY SOUTHWEST OF CA. THE 12Z NAM IS A SLOW OUTLIER WITH THIS INITIAL SYSTEM. REGARDING THE WEAKENING UPPER LOW...THE 00Z CMC IS A TAD WEAKER THAN THE MODEL CONSENSUS. STRONGER MODEL CLUSTERING TENDS TO RESIDE WITH THE 12Z GFS AND 00Z ECMWF AND A BLEND OF THESE SOLUTIONS WILL BE PREFERRED. ...SHORTWAVE TROUGH CROSSING ONTARIO TODAY... ...ENERGY CROSSING THE GREAT LAKES/NORTHERN NEW ENGLAND THROUGH TUES... PREFERENCE: NON-NAM CONSENSUS CONFIDENCE: ABOVE AVERAGE THE 12Z NAM IS A TAD STRONGER THAN THE WELL CLUSTERED GLOBAL MODELS. WILL THEREFORE PREFER A NON-NAM CONSENSUS. ...UPPER TROUGH AND CLOSED LOW DEVELOPMENT OVER THE NORTHWEST BY WED... PREFERENCE: BLEND OF THE 12Z GFS AND 00Z ECMWF CONFIDENCE: SLIGHTLY ABOVE AVERAGE THE 12Z NAM CONTINUES TO BE A TAD TOO WEAK IT APPEARS WITH THE HEIGHT FALLS...WITH THE REMAINING GLOBAL MODELS A BIT STRONGER. THE 12Z GFS AND 00Z ECMWF CLUSTER TOGETHER GENERALLY RATHER WELL AND HAVE GOOD ENSEMBLE SUPPORT...SO WILL PREFER A GFS/ECMWF BLEND. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... ORRISON