MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 138 AM EST SUN JAN 11 2015 VALID JAN 11/0000 UTC THRU JAN 14/1200 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 00Z MODEL EVALUATION...INCLUDING THE NAM/GFS/UKMET/GEM AND ECMWF ...TROUGH OVER TEXAS SHEARING ACROSS THE TENNESSEE VALLEY AND MID ATLANTIC... PREFERENCE: GENERAL MODEL COMPROMISE CONFIDENCE: ABOVE AVERAGE THE LATEST MODELS ARE IN GOOD AGREEMENT WITH THE MASS FIELD DETAILS OF THIS SYSTEM...SO WILL PREFER A GENERAL MODEL COMPROMISE TO RESOLVE ANY SMALLER SCALE DIFFS AT THIS POINT. ...NORTHERN STREAM AFFECTING THE PLAINS/GREAT LAKES/NEW ENGLAND... PREFERENCE: BLEND OF THE 00Z GFS/00Z ECMWF CONFIDENCE: AVERAGE ONE SHORTWAVE TROUGH IS PROGGED TO SWING THROUGH THE GREAT LAKES MONDAY. ADDITIONAL SHORTWAVE ENERGY IS FORECAST TO LOWER HEIGHTS ACROSS THE NORTHERN PLAINS AND UPPER MIDWEST TUESDAY INTO EARLY WEDNESDAY. THE 00Z NAM AND 00Z GEM TEND TO OVERALL BE A BIT SHARPER WITH THE SHORTWAVE ENERGY BY THE END OF THE PERIOD OVER THE REGION COMPARED TO THE 00Z GFS/00Z ECMWF AND 00Z UKMET. THE GFS AND ECMWF CONTINUE TO BEST FIT THE ENSEMBLE MEAN FORECASTS THROUGH THE PERIOD...SO WILL MAINTAIN CONTINUITY AND PREFER A GFS/ECMWF BLEND. ...SOUTHERN CALIFORNIA TROUGH ACCELERATING EASTWARD... PREFERENCE: BLEND OF THE 00Z GFS/00Z ECMWF CONFIDENCE: SLIGHTLY BELOW AVERAGE THIS SYSTEM IS FORECAST TO OPEN AND DE-AMPLIFY AS IT HEADS EAST...REACHING THE TENNESSEE VALLEY BY TUESDAY. THE 00Z NAM AND 00Z UKMET ARE HANGING ON TO A MODESTLY SHARPER SHORTWAVE IMPULSE AS THE ENERGY MOVES INTO THE TENNESSEE VALLEY COMPARED TO THE 00Z GFS AND 00Z ECMWF. THE 00Z GEM HAS TRENDED STRONGER AND SLOWER AND IS THE DEEPEST SOLUTION OVERALL. THE RELATIVELY STRONGER NAM AND ESPECIALLY THE GEM ARE ATTEMPTING TO DRIVE A SOMEWHAT STRONGER SURFACE REFLECTION JUST OFFSHORE THE MID-ATLANTIC COAST BY EARLY WEDNESDAY. BETTER CONTINUITY RESIDES WITH THE GFS AND ECMWF SOLUTIONS FOR THIS LOW AMPLITUDE FEATURE...AND SINCE THE FLOW DOWNSTREAM WILL BE RATHER CONFLUENT ALOFT...THE RELATIVELY FLATTER GFS/ECMWF SOLUTIONS WILL BE PREFERRED. THIS IS ALSO SUPPORTED BY THE 12Z ECENS MEAN AND 00Z GEFS MEAN. CONFIDENCE THOUGH IS A LITTLE LIMITED GIVEN THE INCREASE IN MODEL SPREAD WITH THE 00Z GUIDANCE. ...SHORTWAVE TROUGH REACHING THE NORTHWEST SUNDAY NIGHT... ...AMPLIFYING INTO THE FOUR CORNERS REGION... PREFERENCE: BLEND OF 00Z ECMWF/00Z GEM CONFIDENCE: BELOW AVERAGE THE MODELS ARE CONTINUING TO STRUGGLE WITH THE DETAILS OF A TROUGH CROSSING THE NORTHWEST THAT IS FORECAST TO AMPLIFY INTO THE FOUR CORNERS REGION BEFORE THEN EJECTING OUT INTO THE CENTRAL AND SOUTHERN PLAINS. THE 00Z UKMET IS TENDING TO DRIVE STRONGER HEIGHT FALLS INTO THE FOUR CORNERS REGION THAN ANY OTHER MODEL. THE 00Z NAM IS SEEN AS KEEPING A BIT MORE ENERGY FARTHER NORTH OVER THE CENTRAL ROCKIES BEFORE ENERGY REACHES THE PLAINS. THE BETTER MODEL CLUSTERING WOULD GENERALLY FAVOR THE 00Z ECMWF AND 00Z GEM WHICH HAVE SUPPORT FROM THE 12Z ECENS MEAN. THE 00Z GFS HANGS A LITTLE MORE ENERGY BACK FARTHER WEST OVER THE FOUR CORNERS REGION COMPARED TO THE ECMWF/GEM CAMP...BUT IS NOT SIGNIFICANTLY DIFFERENT. CONFIDENCE IS LIMITED GIVEN THE OVERALL SPREAD...BUT BASED ON CLUSTERING AND ENSEMBLE SUPPORT...A BLEND OF THE ECMWF AND GEM WILL BE FAVORED HERE FOR NOW. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... ORRISON