MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1225 PM EDT SUN SEP 18 2016 VALID SEP 18/1200 UTC THRU SEP 22/0000 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 12Z MODEL EVALUATION...INCLUDING THE NAM AND GFS ...COLD FRONT OVER THE OHIO VALLEY TODAY... ...WEAKENING AS IT REACHES THE EAST COAST... PREFERENCE: GENERAL MODEL COMPROMISE CONFIDENCE: ABOVE AVERAGE NOT CONSIDERING THE LIKELY INTERACTION WITH T.D. JULIA IN A COUPLE DAYS OVER THE SOUTHERN MID-ATLANTIC REGION...THE MODELS SHOW RATHER GOOD AGREEMENT WITH THE EVOLUTION OF THE FRONT AS IT MOVES TOWARD THE EAST COAST. ...T.D. JULIA OFF THE SOUTHEAST COAST... PREFERENCE: SEE LATEST NHC FORECAST ADVISORY THE 15Z NHC ADVISORY FOR JULIA SHOWS THIS SYSTEM BECOMING A REMNANT LOW BY 72 HOURS OR 12Z/21...WITH THE SYSTEM EXPECTED TO ALSO BECOME ABSORBED BY THE APPROACH OF THE AFOREMENTIONED FRONT AND A WELL-DEFINED SHORTWAVE TROUGH THAT WILL MOVE PROGRESSIVELY EAST OUT OF THE MID MS VALLEY AND INTO THE MID-ATLANTIC REGION TUES AND WED. THE ENERGY IS EXPECTED TO MERGE WITH JULIA...RESULTING IN A CLOSED MID LEVEL LOW CENTER OVER THE SOUTHERN MID-ATLANTIC REGION. THE LATEST NHC FORECAST IS CLOSE TO THE GLOBAL MODEL CONSENSUS...WITH THE 00Z ECMWF A BIT FARTHER SOUTH AND SLOWER...AND THE 12Z GFS AND 00Z UKMET FARTHER NORTH AND FASTER AND SUGGESTING MORE SIGNIFICANT IMPACTS ON EASTERN NC. THE 12Z NAM IS A LITTLE LEFT OF THE GLOBAL MODEL CONSENSUS...WITH THE 00Z CMC MUCH FARTHER TO THE RIGHT AND FASTER TO TAKE JULIA AWAY FROM THE EAST COAST. PLEASE CONSULT THE LATEST NHC FORECAST ADVISORY FOR MORE DETAILS. ...T.S. PAINE SOUTH OF BAJA CALIFORNIA... PREFERENCE: SEE LATEST NHC FORECAST ADVISORY THE 00Z ECMWF IS FARTHEST LEFT WITH THE TRACK OF T.S. PAINE OVER THE NEXT 2 TO 3 DAYS. THE NHC TRACK IS CLOSEST TO A BLEND OF THE 12Z GFS AND 00Z UKMET WHICH IS A BIT FARTHER EAST AND RELATIVELY CLOSER TO THE BAJA PENINSULA. THE 12Z NAM APPEARS TO BE TOO SLOW AND POSSIBLY TOO FAR TO THE LEFT JUST LIKE THE ECMWF SOLUTION. THE NHC FORECAST CALLS FOR PAINE TO BECOME A REMNANT LOW AT 72 HOURS OR 12Z/21. PLEASE CONSULT THE LATEST NHC FORECAST ADVISORY FOR MORE DETAILS. ...SHORTWAVE OVER THE CENTRAL PLAINS/MID MS VALLEY... ...ENERGY REACHING THE MID-ATLANTIC ON MON... PREFERENCE: BLEND OF THE 12Z GFS AND 00Z ECMWF CONFIDENCE: AVERAGE SHORTWAVE ENERGY EJECTING EAST FROM THE CENTRAL PLAINS AND MID MS VALLEY WILL MOVE EAST INTO THE MID-ATLANTIC REGION ON MON AND AS MENTIONED BEFORE WILL BEGIN TO INTERACT WITH A FRONTAL ZONE AND T.D. JULIA. REGARDING THE SHORTWAVE ENERGY...THE BETTER MODEL CLUSTERING RESIDES WITH THE 12Z GFS AND 00Z ECMWF....AND THUS A BLEND OF THESE SOLUTIONS WILL BE PREFERRED. ...WEAK MID-LEVEL LOW SOUTH OF LOUISIANA THIS MORNING... PREFERENCE: GENERAL MODEL COMPROMISE CONFIDENCE: ABOVE AVERAGE THIS SYSTEM IS EXPECTED TO DROP SLOWLY SOUTHWARD OVER THE NEXT COUPLE OF DAYS AND WILL WEAKEN. ALL OF THE MODELS AGREE IN THIS SCENARIO AND THUS A GENERAL MODEL COMPROMISE WILL BE PREFERRED. ...MID-UPPER LEVEL LOW SOUTH OF CA... ...ENERGY WEAKENING AND TRACKING INTO THE SOUTHWEST BY TUES... PREFERENCE: GENERAL MODEL COMPROMISE CONFIDENCE: SLIGHTLY ABOVE AVERAGE DESPITE SOME MINOR MASS FIELD DIFFERENCES...THE MODELS COMPARE RATHER WELL WITH THIS SYSTEM. ...SHORTWAVE TROUGH CROSSING THE NORTHERN PLAINS TODAY... ...ENERGY CROSSING THE GREAT LAKES/NORTHERN NEW ENGLAND THROUGH TUES... PREFERENCE: GENERAL MODEL COMPROMISE CONFIDENCE: AVERAGE THE MODELS ARE IN GOOD AGREEMENT WITH THIS SYSTEM...AND SO A GENERAL MODEL COMPROMISE WILL BE PREFERRED WITH THIS SYSTEM. ...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 00Z CMC IN PARTICULAR STANDS OUT AS AN OUTLIER FROM THE REMAINING MODELS WITH A SLOWER AND DEEPER SOLUTION REGARDING THIS FEATURE. THE 12Z NAM IS ALSO A LITTLE SLOWER WITH ENERGY DIGGING SOUTHEAST INTO THE WEST COAST. STRONGER MODEL CLUSTERING RESIDES OVERALL WITH THE 12Z GFS AND 00Z ECMWF...AND THUS A BLEND OF THESE SOLUTIONS WILL BE PREFERRED. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... ORRISON