MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 113 AM EDT TUE MAY 19 2015 VALID MAY 19/0000 UTC THRU MAY 22/1200 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. ...LEAD SHORTWAVE LIFTING ACROSS THE CENTRAL ROCKIES BY 20/0000Z... PRELIMINARY PREFERENCE: GENERAL MODEL COMPROMISE FORECAST CONFIDENCE: ABOVE AVERAGE THE GUIDANCE SHOW THIS FEATURE LIFTING FROM SOUTHERN AZ UP TOWARD THE CENTRAL ROCKIES DURING THE NEXT 24 HOURS. AT THIS POINT THE SYSTEM SHOULD GRADUALLY SHEAR OVER THE GREAT PLAINS WHILE SOME OF THE SHORTWAVE ENERGY MERGES WITH THE ACTIVE NORTHERN STREAM TROF. HEIGHTS ARE EXPECTED TO RISE IN ITS WAKE ACROSS THE ROCKIES. OVERALL...MODEL SOLUTIONS ARE PRETTY WELL CLUSTERED TO SUPPORT A GENERAL MODEL COMPROMISE. ...SERIES OF NORTHERN STREAM IMPULSES CROSSING THE GREAT LAKES AND NEW ENGLAND... ...SURFACE LOW EMERGING OFF THE CAROLINAS LATE IN THE PERIOD... PRELIMINARY PREFERENCE: BLEND OF THE 00Z NAM/12Z ECMWF WITH THE 12Z ECMWF ENSEMBLE MEAN FORECAST CONFIDENCE: AVERAGE BROAD CYCLONIC FLOW WILL ANCHOR ITSELF ACROSS THE NORTHEASTERN CORRIDOR OF THE CONTINENT AS A SERIES OF SHORTWAVES TRAVERSE THROUGH THE GREAT LAKES AND NEW ENGLAND THE NEXT COUPLE OF DAYS. THE MODELS SHOW SOME VARIABILITY BY 22/0000Z REGARDING A SHORTWAVE RACING FROM THE UPPER GREAT LAKES TOWARD THE MID-ATLANTIC. THE 00Z NAM IS A BIT MORE AMPLIFIED WITH THE UPPER FLOW WHICH LEADS TO A SLIGHTLY DEEPER SURFACE SOLUTION OFFSHORE OF THE SOUTHEASTERN U.S. REGARDING THIS SURFACE DEVELOPMENT...THE 00Z GFS DOES NOT SEEM TO JOIN THE OTHERS AND HANGS ON THE WITH THE MORE SOUTHERN SOLUTION SUGGESTED BY ITS 18Z GEFS MEAN. THESE APPEAR TO BE OUTLYING BASED ON THE ENSEMBLE LOW PLOTS. WHILE THE 00Z NAM WAS A TAD DEEPER WITH THE PATTERN...IT DOES SHOW A GREAT DEAL OF SUPPORT FOR THE 12Z ECMWF/ECMWF ENSEMBLE MEAN. WILL RECOMMEND A COMBINATION OF THESE MODELS AND RE-ASSESS AS NEWER GUIDANCE ARRIVES. ...NEXT PACIFIC TROF SLIDING INTO THE SOUTHWESTERN U.S. BY 22/1200Z... PRELIMINARY PREFERENCE: BLEND OF THE 12Z ECMWF/ECMWF ENSEMBLE MEAN FORECAST CONFIDENCE: SLIGHTLY ABOVE AVERAGE YET ANOTHER UPPER LOW IS FORECAST TO AFFECT THE SOUTHWESTERN CORRIDOR OF THE COUNTRY BY LATER IN THE WEEK. THERE IS PRETTY STRONG AGREEMENT IN THE SPAGHETTI PLOTS WITH GOOD CLUSTERING NOTED IN THE 564-DM PLOT. THE MOST CONSISTENT SOLUTION IN THE PAST FEW MODEL CYCLES HAS BEEN THE ECMWF ENSEMBLE MEMBERS. WILL LEAN ON THE ECMWF SUITE GIVEN SUCH CONSISTENCY HERE. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... RUBIN-OSTER