MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1222 AM EDT WED OCT 01 2014 VALID OCT 01/0000 UTC THRU OCT 04/1200 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 00Z MODEL EVALUATION...INCLUDING THE NAM AND GFS ...NEG-TILTING TROUGH/SURFACE LOW LIFTING THROUGH THE NORTHERN PLAINS... PREFERENCE: GENERAL MODEL COMPROMISE CONFIDENCE: ABOVE AVERAGE ALL OF THE MODELS SHOW A NEG-TILTING TROUGH AND ASSOCD CLOSED LOW PIVOTING NWD UP THROUGH THE NRN PLAINS THROUGH WED ALONG WITH A COMPACT AREA OF SFC LOW PRESSURE. THE MODELS SHOW SUFFICIENT LARGE SCALE AGREEMENT SUCH THAT A GENERAL MODEL COMPROMISE CAN BE PREFERRED ATTM TO RESOLVE ANY SMALLER SCALE DIFFS. ...POWERFUL TROUGH/CLOSED LOW EXPECTED TO DEVELOP OVER THE GREAT LAKES/MIDWEST... ...SHEARING SOUTHERN STREAM ENERGY OVER THE SOUTHERN PLAINS... PREFERENCE: BLEND OF THE 00Z GFS/12Z ECMWF AND 12Z UKMET CONFIDENCE: AVERAGE THE MODELS INDICATE A VERY STRONG NORTHERN STREAM TROUGH DIGGING INTO THE NRN PLAINS AND UPR MIDWEST THURS AND FRI WHICH WILL ASSUME SOME NEG TILT AND SHOULD CLOSE OFF. MEANWHILE...A SRN STREAM TROUGH ASSOCD WITH AT LEAST A PERIOD OF SPLIT FLOW OVER THE CNTRL U.S. WILL BE DIGGING ACROSS THE ROCKIES AND DOWN INTO THE SRN PLAINS AND LWR MS VLY BEFORE GRADUALLY BE ABSORBED BY THE MORE DOMINANT NRN STREAM ENERGY. ACROSS THE NRN PLAINS AND UPR MIDWEST...THE TREND HAS BEEN FOR A STRONGER NRN STREAM TROUGH TO DEVELOP...WITH A CLOSED LOW THAT SHOULD DIVE SEWD ACROSS THE MIDWEST AND TWD THE OH VLY BY SAT...AND A SEPARATE CLOSED LOW DEVELOPING BACK OVER THE UPR GRT LAKES REGION. THE 00Z GFS AND 12Z UKMET ARE TRENDING TWD THE 12Z ECMWF SOLN WITH REGARDING DEPTH...ALTHOUGH THE 12Z ECMWF IS NOTABLY FASTER TO SPREAD STRONG HEIGHT FALLS INTO THE OH VLY. THE 00Z NAM AND 12Z GEM SUGGEST THE FOCUS OF ANY CLOSED LOW FEATURE WILL BE OVER THE GRT LAKES REGION...WITH ANYTHING FARTHER SOUTH BEING WEAK AND ILL-DEFINED ASIDE FROM THE LARGER SCALE TROUGH AXIS. REGARDING THE SRN STREAM TROUGH...ALL OF THE MODELS DEPICT A PROGRESSIVE SHORTWAVE TROUGH THAT WILL DIG THROUGH THE CNTRL/SRN ROCKIES AND QUICKLY OUT ACROSS THE SRN PLAINS AND LWR MS VLY BEFORE BECOMING SHEARED APART AND ABSORBED BY THE MORE POWERFUL NRN STREAM HEIGHT FALLS. BASED ON THE COLLECTIVE TRENDS SEEN OVER THE LAST DAY OR SO...IT WOULD APPEAR THAT A MORE AGGRESSIVE SOLN COMPARABLE TO THE ECMWF IS BECOMING MORE LIKELY. THE ECMWF MAY BE TOO FAST WITH ITS HEIGHT FALLS...AND SO TO MITIGATE THIS...WILL PREFER A GFS/ECMWF AND UKMET BLEND. ...UPPER TROUGH/CLOSED LOW IMPACTING THE NORTHERN MID-ATLANTIC AND SOUTHERN NEW ENGLAND... PREFERENCE: BLEND OF THE 12Z GEM AND 12Z ECENS MEAN CONFIDENCE: SLIGHTLY BELOW AVERAGE THE MODELS TAKE THE SLOW MOVING CLOSED LOW OVER THE NRN MID-ATLANTIC REGION OFF TO THE EAST INTO SRN NEW ENGLAND ON WED AND SLOWLY OFFSHORE THROUGH FRI. THE MODELS OVERALL HAVE TRENDED MORE AGGRESSIVE WITH OFFSHORE SFC LOW DEVELOPMENT AND HAVE A NOTABLE INVERTED TROUGH THAT EXTENDS BACK WWD TWD AREAS JUST SOUTH OF SRN NEW ENGLAND AND NEAR THE BENCHMARK WED NIGHT AND THURS. BY FRI AND SAT...THE 12Z ECMWF HANGS ITS CLOSED LOW FARTHER BACK TO THE WEST...WITH THE 00Z NAM/00Z GFS AND 12Z UKMET ALL QUICKER TO SEND THE ENERGY FARTHER OFFSHORE AND AWAY FROM NEW ENGLAND. THE 12Z GEM SPLITS THE DIFF. THE LATEST GEFS MEAN SUPPORTS THE RELATIVELY MORE CONSENSUS CAMP...WITH THE ECENS MEAN A LITTLE EAST OF THE DETERMINISTIC ECMWF AND CLOSE TO THE GEM SOLN. AS A COMPROMISE...WILL PREFER A BLEND OF THE GEM AND ECENS MEAN. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... ORRISON