MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 244 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/GFS/UKMET/GEM AND THE ECMWF ...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: GENERAL MODEL COMPROMISE 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 ARE NOT REALLY ANY SUBSTANTIAL MASS FIELD DIFFERENCES. THE 00Z MODELS HAVE COME INTO SUFFICIENTLY GOOD ENOUGH AGREEMENT NOW THAT A GENERAL MODEL COMPROMISE WILL BE PREFERRED TO RESOLVE ANY SMALLER SCALE DIFFS. ...WEAK TROUGH OVER THE GULF COAST STATES EXITING OFFSHORE THE SOUTHEAST COAST... ...WEAK SURFACE LOW OVER THE NORTHEAST GULF OF MEXICO... PREFERENCE: NON-GEM CONSENSUS 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 GEM IS NOW THE STRONGEST COMPARED TO THE GLOBAL MODEL CONSENSUS. THE 00Z NAM/00Z GFS/00Z ECMWF AND 00Z UKMET ARE CLUSTERING MUCH BETTER NOW WITH THE SFC LOW EVOLUTION. A NON-GEM CONSENSUS WILL BE PREFERRED ATTM AS A RESULT FOR MASS FIELDS. HOWEVER...PLS NOTE THAT THE 00Z GFS IN PARTICULAR CONTINUES TO SUFFER SOMEWHAT FROM CONVECTIVE FEEDBACK WHICH IS DISRUPTING ITS QPF. PLS CONSULT THE LATEST QPFPFD FOR MORE DETAILS ON THE MODEL PREFERENCES FOR QPF. ...DEEP TROUGH/CLOSED LOW OVER THE WEST EJECTING OUT INTO THE NORTHERN PLAINS... PREFERENCE: BLEND OF THE 00Z UKMET/00Z GEM AND THE 00Z ECMWF 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 IS THE FASTEST TO LIFT THE ENERGY NWD. THE 00Z GFS IS THE SLOWEST BUT IS SUPPORTED BY THE LATEST GEFS MEAN. THE ECENS MEAN FAVORS A CONSENSUS OF THE 00Z ECMWF/00Z GEM AND 00Z UKMET WHICH CLUSTER WELL AND SPLIT THE DIFF BETWEEN SLOWER GFS AND FASTER NAM. A BLEND OF THE NON-NCEP MODELS WILL BE PREFERRED. ...UPPER TROUGH CROSSING THE PACIFIC NORTHWEST AND DIGGING ACROSS THE ROCKIES/HIGH PLAINS BY WED... PREFERENCE: BLEND OF THE 00Z NAM/00Z GFS AND 00Z UKMET CONFIDENCE: SLIGHTLY BELOW AVERAGE THE 00Z GEM AND TO SOME EXTENT THE 00Z NAM ARE MORE AMPLIFIED WITH THE UPPER TROUGH AS IT CROSSES THE CNTRL ROCKIES ON TUES...WITH THE 00Z ECMWF THE WEAKEST AND MOST PROGRESSIVE. THERE HAS BEEN A GENERAL TREND IN THE 00Z GUIDANCE TO SHOW A BIT MORE AMPLIFICATION OF SHORTWAVE ENERGY OVER THE FOUR CORNERS REGION BY THURS...WITH SOME HINT AT STREAM SEPARATION. THE SREF MEAN...GEFS MEAN AND ECENS MEAN DO NOT QUITE YET SUPPORT A WELL-DEFINED SHORTWAVE SEPARATING OUT AND AMPLIFYING OVER THE CNTRL ROCKIES AND SRN HIGH PLAINS...BUT WITH THE STRONGER TRENDS NOTED AND WITH THE FACT THAT ENERGY OVER THE NRN PLAINS WILL BE LIFTING NEWD ALONG THE BORDER AND INTO CANADA...THERE IS ROOM FOR SOME STREAM SEPARATION TWD THE SRN HIGH PLAINS. WILL PREFER A BLEND OF THE 00Z NAM/00Z GFS AND 00Z UKMET AS A RESULT. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... ORRISON