MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 243 PM EDT MON SEP 29 2014 VALID SEP 29/1200 UTC THRU OCT 03/0000 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... ============================================== 12Z MODEL EVALUATION AND PREFERENCES ============================================== NAM/GFS INITIALIZATION ERRORS DO NOT APPEAR TO SIGNIFICANTLY AFFECT THEIR LARGE SCALE OUTPUT. ============================================== ...CYCLOGENESIS IN THE NORTHERN PLAINS... PREFERENCE: BLEND OF THE OPERATIONAL MODELS CONFIDENCE: ABOVE AVERAGE AT THE LEADING EDGE OF A LARGE SCALE TROUGH...A SMALLER SCALE CYCLONE WILL EVOLVE OVER THE NORTHERN PLAINS BEFORE LIFTING INTO CANADA. MODELS SHOW STRONG AGREEMENT AS TO THE DETAILS. ...SHORTWAVES DIGGING THROUGH THE ROCKIES AND PLAINS WED/THU... PREFERENCE: 12Z GFS CONFIDENCE: AVERAGE THE FORECAST HERE IS MADE PARTICULARLY CHALLENGING BY EXISTENCE OF A SPLIT STREAM WITHIN NORTHWESTERLY FLOW AND GROWING SEPARATION BETWEEN THE GEFS MEAN AND THE LATEST AVAILABLE 00Z ECMWF ENSEMBLE MEAN FOR FORECASTS VERIFYING 00Z FRIDAY. CONFIDENCE IN A GFS-LIKE SOLUTION IS INCREASED...HOWEVER...BY DISTINCT TRENDS IN A HEALTHY MAJORITY OF THE GUIDANCE. THE GFS AND NAM HAVE SHOWN AGREEMENT WITH ONE ANOTHER AND RUN TO RUN CONSISTENCY IN THE 29/00Z TO 29/06Z AND 29/12Z RUNS. THEY ARE SUPPORTED BY THE GEFS MEAN AND THE NAEFS MEAN WHICH INCORPORATES THE CANADIAN MODELING CENTER ENSEMBLE. MORE RECENTLY THE 12Z UKMET TRENDED STRONGLY TOWARD THE NAM/GFS. THE OPERATIONAL CANADIAN CONTINUES AS A DEEP OUTLIER DEPICTING STRONG HEIGHT FALLS INTO SOUTHWEST TEXAS ON THURSDAY...BUT IT DOES ERR ON THE SIDE OF SLOWER AND DEEPER. VIEWING ALL THE GUIDANCE TOGETHER...THE ECMWF STILL APPEARS TO BE A LESS LIKELY SOLUTION...BEING TOO FAST AND OF LESSER AMPLITUDE. IT IS WORTH NOTING...HOWEVER...THAT THE 12Z ECMWF DID TREND SLIGHTLY SLOWER. OUR PREFERRED MODEL CLUSTER...THAT WHICH SUPPORT THE GFS...HAS SHOWN A DISTINCT TREND TOWARD THE SLOWER AND MORE AMPLIFIED SOLUTION IN THE SOUTHERN PLAINS...AND ALSO A BREAKDOWN OF SHORTWAVE RIDGING ALONG THE WEST COAST OF BRITISH COLUMBIA THURSDAY. ALTHOUGH PERHAPS NOT DIRECTLY RELATED...SEEING AGREEMENT IN THE TRENDS AT TWO KEY PLACES ON THE MAP GIVES US INCREASED CONFIDENCE THAT THE TRENDS ARE MEANINGFUL. WITH THE NAM/UKMET BEING A BIT DEEPER/STRONGER IN THE PLAINS...WE RECOMMEND THE SOMEWHAT MORE CONSERVATIVE 12Z GFS. ...SHORTWAVE TROUGH DIGGING INTO THE MID-ATLANTIC/SOUTHERN NEW ENGLAND... PREFERENCE: 12Z ECMWF CONFIDENCE: ABOVE AVERAGE HERE MODEL DIFFERENCES ARE MINOR. THERE ARE NO OUTLIERS...AND ONE COULD RECOMMEND A BLEND OF THE OPERATIONAL MODELS. WE HAVE A SLIGHT PREFERENCE TOWARD THE ECMWF AND ECMWF ENSEMBLE MEAN...WHICH MAINTAIN A CLOSED LOW FOR LONGER DURATION AND DRIFTING AT A SLIGHTLY SLOWER PACE. THIS WOULD SEEM FAVORED BY ITS POSITION WITHIN A LARGER SCALE SHORTWAVE RIDGE. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... BURKE