MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 108 PM EDT SAT AUG 08 2015 VALID AUG 08/1200 UTC THRU AUG 12/0000 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 12Z NAM/GFS EVALUATION...INCLUDING PRELIMINARY PREFERENCES ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ UPPER TROUGHING IMPACTING NEW ENGLAND THROUGH SUN SURFACE LOWS EXITING OFF THE EAST COAST ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GENERAL MODEL COMPROMISE CONFIDENCE: ABOVE AVERAGE NO SIGNIFICANT MODEL DIFFERENCES WERE NOTED WITH THE UPPER TROUGH THAT CROSSES NEW ENGLAND THIS WEEKEND. ANY SURFACE LOW DIFFERENCES IN THE WESTERN ATLANTIC DEVELOP AT A POINT WHICH IMPACTS ARE NEGLIGIBLE TO THE CONUS. UPPER TROUGH CROSSING THE GREAT BASIN TO THE NORTHERN PLAINS ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GENERAL MODEL COMPROMISE CONFIDENCE: ABOVE AVERAGE NO SIGNIFICANT DIFFERENCES WERE NOTED WITH THIS SYSTEM SO A GENERAL MODEL COMPROMISE IS PREFERRED. UPPER TROUGH/CLOSED LOW CURRENTLY OVER SOUTHERN CANADA ENERGY AMPLIFYING INTO THE GREAT LAKES/NORTHEAST AROUND TUESDAY SURFACE LOW LIFTING FROM THE PLAINS/MIDWEST TO THE NORTHEAST ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: BLEND OF THE 12Z GFS AND 00Z ECMWF CONFIDENCE: SLIGHTLY ABOVE AVERAGE THE SREF/GEFS/ENSEMBLE MEANS SHOW VERY GOOD AGREEMENT THROUGH TUE WITH THE EVOLUTION OF A LARGE SCALE UPPER TROUGH FORECAST TO DEVELOP OVER THE NORTHEASTERN QUADRANT OF THE U.S. AND WITH THE TRACK OF A SURFACE LOW FROM THE MIDWEST (MON MORNING) TO NEW YORK STATE (TUE MORNING). THE 12Z GFS AND 00Z ECMWF ARE CLOSEST TO THE MEANS AT ALL TIMES...BUT THE 00Z ECMWF APPEARS TO BE A BIT TOO WEAK WITH THE 850 MB REFLECTION OF THE LOW ACROSS THE MIDWEST EARLY ON MON. THE NAM SURFACE LOW DEPICTION IS RATHER ILL DEFINED COMPARED TO THE REMAINING MODELS AND THE 00Z UKMET/CMC DO NOT MATCH WELL WITH THE PLACEMENT OF THE MEANS. UPPER TROUGH DIGGING DOWN OFF THE WEST COAST THIS WEEKEND ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GENERAL MODEL COMPROMISE CONFIDENCE: SLIGHTLY ABOVE AVERAGE THE MODELS ARE IN GOOD AGREEMENT IN TAKING AN UPPER LOW SOUTHEAST FROM THE GULF OF AK TOWARDS COASTAL AREAS OF BRITISH COLUMBIA ON SAT AND THEN WITH HEIGHT FALLS DROPPING QUICKLY SOUTH OFF THE WEST COAST THROUGH MON AND TUE. BY TUE EVENING...THERE ARE SOME MINOR PLACEMENT DIFFERENCES WITH THE UPPER LOW WITH THE 12Z NAM FARTHEST OFFSHORE AND THE 00Z UKMET CLOSEST TO THE CA COAST. THE LATEST ENSEMBLE MEANS SHOW BROAD AGREEMENT AND ARE CENTERED NEAR THE DETERMINISTIC MODEL CONSENSUS. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... OTTO