MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1157 PM EST WED NOV 04 2015 VALID NOV 05/0000 UTC THRU NOV 08/1200 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... ...AN EVALUATION OF THE 00Z NAM/GFS ALONG WITH PRELIMINARY PREFERENCES/FORECAST CONFIDENCE... THERE DID NOT APPEAR TO BE ANY INITIALIZATION ERRORS WITH THE 00Z NAM/GFS DEEMED SIGNIFICANT ENOUGH TO IMPACT THEIR FORECASTS. ...LINGERING SHORTWAVE/SURFACE WAVE IN THE VICINITY OF COASTAL NC... PRELIMINARY PREFERENCE: GENERAL MODEL COMPROMISE FORECAST CONFIDENCE: ABOVE AVERAGE A WEAK MID-LEVEL PERTURBATION IN THE FLOW EXISTS ACROSS THE OUTER BANKS OF NC. THERE IS SOME HINT OF A DIFFUSE SURFACE WAVE JUST OFF THE COAST BUT THIS SHOULD DISSIPATE BY THURSDAY AFTERNOON. OVERALL...MODELS ARE IN CLOSE ENOUGH AGREEMENT DURING THE BRIEF PERIOD THIS SYSTEM AFFECTS THE U.S. THAT A GENERAL MODEL COMPROMISE SUFFICES HERE. ...STRONG UPPER TROUGH MIGRATING FROM THE FOUR CORNERS REGION TO THE GREAT LAKES... ...ASSOCIATED COLD FRONT/STRENGTHENING AREA OF LOW PRESSURE... PRELIMINARY PREFERENCE: BLEND OF THE 00Z GFS/12Z ECMWF FORECAST CONFIDENCE: SLIGHTLY BELOW AVERAGE AMPLIFIED FLOW ACROSS THE CONUS FEATURES A DEEP UPPER TROUGH ANCHORING THE INTERMOUNTAIN WEST/ROCKY MOUNTAIN REGION. THIS SYSTEM IS EXPECTED TO QUICKLY LIFT NORTHEASTWARD REACHING THE GREAT LAKES REGION BY EARLY FRIDAY. THE CORE OF THE STRONGEST HEIGHT FALLS SHOULD PUSH INTO SOUTHEASTERN CANADA AS A DOMINANT SUBTROPICAL RIDGE MAINTAINS HIGHER MID-LEVEL HEIGHTS OVER THE SOUTHEASTERN U.S. IT APPEARS THE 00Z NAM IS SLOWER THAN OTHER SOLUTIONS WITH THE PROGRESSION OF THE COLD FRONT THROUGH THE OH RIVER VALLEY. FARTHER TO THE SOUTH...THERE ARE QUITE A BIT OF DIFFERENCES WITH THE TIMING/ORIENTATION OF THE BOUNDARY THROUGH THE SOUTHERN U.S. IN PARTICULAR...THE 12Z CMC IS QUICKER AND MORE SOUTH/NORTH ORIENTED THAN THE ENSEMBLE SOLUTIONS. A FAIR COMPROMISE BETWEEN THE TWO REGIONS OF DIFFERENCES IS TO USE A COMBINATION OF THE 00Z GFS/12Z ECMWF. ...SECONDARY TROUGH CROSSING THE CENTRAL U.S. BY FRIDAY... ...POTENTIAL SURFACE LOW DEVELOPMENT ALONG THE CENTRAL GULF COAST... PRELIMINARY PREFERENCE: BLEND OF THE 18Z GEFS/21Z SREF MEANS FORECAST CONFIDENCE: BELOW AVERAGE AS THE LEAD SHORTWAVE RACES TOWARD SOUTHERN ONTARIO...ADDITIONAL TRAILING HEIGHT FALLS MOVE FROM THE NORTHERN ROCKIES INTO THE CENTER OF THE COUNTRY. THIS SECONDARY SURGE EVENTUALLY HELPS FORCE THE FRONT ALONG THE SOUTHERN TIER OF THE U.S. INTO THE GULF OF MX. THE TIMING OF THE UPPER TROUGH IS QUITE UNCERTAIN AS NOTED IN THE CHAOTIC 576-DM SPAGHETTI PLOT. ADDITIONALLY...THERE ARE UNCERTAINTIES REGARDING POSSIBLE LOW DEVELOPMENT ALONG THE CENTRAL GULF COAST. ENSEMBLE LOW PLOTS SHOW THE ECMWF SUITE IS THE ONLY CLUSTER OF SOLUTIONS SUPPORTING SUCH A LOW FORMATION. THIS HAS BEEN A CONSISTENT SCHEME IN THE PAST FEW CYCLES OF THE ECMWF. OVERALL...THIS IS A FAIRLY LOW CONFIDENCE FORECAST GIVEN THE POOR DETERMINISTIC AGREEMENT AND VAST ENSEMBLE SPREAD. GIVEN THE LACK OF CONFIDENCE IN THE LOW DEVELOPMENT IN THE ECMWF SUITE...WILL FAVOR THE OTHER ENSEMBLE MEANS. THAT IS...A BLEND OF THE 18Z GEFS/21Z SREF MEANS. ...PACIFIC SYSTEM REACHING THE NORTHWESTERN STATES BY 08/1200Z... ...ADVANCING COLD FRONT... PRELIMINARY PREFERENCE: BLEND OF THE 12Z ECMWF WITH THE 12Z ECMWF ENSEMBLE/21Z SREF MEANS FORECAST CONFIDENCE: AVERAGE AN AMPLIFIED UPPER TROUGH MOVING THROUGH THE PACIFIC NORTHWEST BY LATE IN THE WEEKEND IS REASONABLY WELL RESOLVED BY THE MODEL SUITES. THE RATHER STABLE ENSEMBLE SOLUTIONS SUGGEST THE 00Z NAM/12Z CMC ARE TOO SLOW WITH THE EVOLUTION OF THIS SYSTEM. THE 12Z ECMWF ENSEMBLE/21Z SREF MEANS CLUSTER WELL WITH AGREEMENT SHOWN BY THE 12Z ECMWF. THE RECOMMENDATION IS A COMBINATION OF THESE SOLUTIONS. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... RUBIN-OSTER