MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1200 AM EDT MON SEP 29 2014 VALID SEP 29/0000 UTC THRU OCT 02/1200 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 00Z MODEL EVALUATION...INCLUDING THE NAM AND GFS ...WEAK CLOSED LOW/TROUGH MOVING FROM THE MIDWEST TO THE MID-ATLANTIC BY MON... PREFERENCE: GENERAL MODEL COMPROMISE CONFIDENCE: ABOVE AVERAGE ONLY MINOR MODEL DIFFERENCES REMAIN WITH THIS FEATURE SO A GENERAL MODEL COMPROMISE IS RECOMMENDED TO SMOOTH OUT ANY OF THE SHORT TERM DIFFERENCES. ...SHORTWAVE TROUGH DIGGING INTO THE MID-ATLANTIC/SOUTHERN NEW ENGLAND BY WED... PREFERENCE: 12Z ECMWF CONFIDENCE: ABOVE AVERAGE A SIGNIFICANT TREND HAS BEEN SEEN IN THE GUIDANCE TO BE MORE AMPLIFIED WITH THIS WAVE...MORE LIKE THE ECMWF AS THE UPPER WAVE CROSSES THE GREAT LAKES AND DIGS SEWD BY WED INTO THE NRN MID-ATLANTIC AND SRN NEW ENGLAND. THERE IS NOT REALLY ANY SUBSTANTIAL MASS FIELD DIFFERENCES...BUT THE 12Z UKMET IS PERHAPS A LITTLE FARTHER NORTH OVER NEW ENGLAND BY WED NIGHT WITH ITS CLOSED LOW COMPARED TO THE MULTI-MODEL CONSENSUS. THE 00Z NAM AND 00Z GFS ARE PERHAPS A TAD STRONGER THAN THE 12Z ECMWF...BUT THE 12Z GEM TENDS TO MORE STRONGLY CLUSTER WITH THE ECMWF. SINCE THE ECMWF HAS BEEN SO CONSISTENT WITH THIS FEATURE THE LAST COUPLE OF DAYS...WILL FAVOR A SOLN TWD THE ECMWF. ...WEAK TROUGH OVER THE GULF COAST STATES EXITING OFFSHORE THE SOUTHEAST COAST... ...WEAK SURFACE LOW OVER THE NORTHEAST GULF OF MEXICO... PREFERENCE: 12Z ECMWF CONFIDENCE: AVERAGE ALL OF THE MODELS REMAIN MORE SUPPRESSED WITH A WEAK SURFACE LOW THAT WILL DEVELOP BY EARLY MON OVER THE NERN GULF OF MEXICO AND THEN MOVE NEWD OFFSHORE THE SOUTHEAST COAST MON NIGHT AND TUES. THE 00Z NAM APPEARS A LITTLE TOO WEAK WITH THE WAVE FEATURE...WITH THE 12Z GEM AND 12Z UKMET TOO STRONG. THE 12Z UKMET IS ALSO LIKELY A LITTLE TOO FAST. THE 00Z GFS AND THE 12Z ECMWF SPLIT THE DIFF BUT AT LEAST CLUSTER QUITE WELL. ONE PROBLEM THOUGH WITH THE GFS IS THAT IT CONTINUES TO EXHIBIT SOME CONVECTIVE FEEDBACK...AND AS A RESULT THE ECMWF WILL BE THE PREFERRED SOLN. ...DEEP TROUGH/CLOSED LOW OVER THE WEST EJECTING OUT INTO THE NORTHERN PLAINS... PREFERENCE: BLEND OF THE 12Z ECMWF AND 12Z GEM CONFIDENCE: SLIGHTLY ABOVE AVERAGE THE MODELS ARE IN VERY GOOD AGREEMENT IN TAKING THE CURRENT CLOSED LOW OVER THE WEST EASTWARD ACROSS THE CNTRL ROCKIES WHERE THEN THE BROADER UPR TROUGH IS EXPECTED TO PIVOT NEWD AND GO NEG TILT OVER THE NRN PLAINS BY TUES. THE MODELS ALL SHOW AN AREA OF LOW PRESSURE ASSOCD WITH THE HEIGHT FALLS THAT WILL STRENGTHEN IN THE LEE OF THE ROCKIES AND LIFT NWD INTO SRN CANADA BY WED. THE 00Z NAM AND 12Z UKMET ARE FASTEST TO LIFT THE ENERGY NWD. THE 00Z GFS IS JUST A TAD SLOWER. OVERALL THE GEFS MEAN AND ECENS MEAN FAVOR THE CONSENSUS OF THE 12Z ECMWF AND 12Z GEM CAMP WHICH SPLIT THE DIFF BETWEEN SLOWER AND FASTER CAMPS...AND ARE REASONABLY WELL CLUSTERED. A BLEND OF THE ECMWF AND GEM WILL BE PREFERRED. ...UPPER TROUGH CROSSING THE PACIFIC NORTHWEST AND DIGGING ACROSS THE ROCKIES/HIGH PLAINS BY WED... PREFERENCE: BLEND OF THE 12Z ECMWF AND 12Z UKMET CONFIDENCE: AVERAGE THE 12Z GEM AND TO SOME EXTENT THE 00Z NAM APPEAR JUST A BIT MORE AMPLIFIED WITH THE UPPER TROUGH AS IT CROSSES THE CNTRL ROCKIES ON TUES...WITH THE 12Z ECMWF AND 12Z UKMET A LITTLE WEAKER AND GENERALLY A LITTLE MORE PROGRESSIVE. THE 00Z GFS SPLITS THE DIFF BETWEEN CAMPS. WILL FAVOR A BLEND OF THE 12Z ECMWF AND 12Z UKMET WHICH HAVE BETTER SUPPORT FOR NOW FROM THE LATEST GEFS MEAN AND THE ECENS MEAN. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... ORRISON