MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1248 PM EDT MON JUN 29 2015 VALID JUN 29/1200 UTC THRU JUL 03/0000 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 12Z NAM/GFS EVALUATION WITH PRELIMINARY PREFERENCES ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ NAM/GFS INITIALIZATION ERRORS DO NOT SEEM TO DEGRADE THEIR SHORT RANGE FORECASTS. SHORTWAVE TROUGH/SURFACE LOW MOVING ACROSS THE GREAT LAKES LATE TUE/EARLY WED ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~ PREFERENCE: GFS/00Z ECMWF COMPROMISE CONFIDENCE: AVERAGE BY LATE TUE ACROSS THE UPPER GREAT LAKES...THE NAM APPEARS TO BE THE OUTLIER HERE...WITH A SLOWER/MORE AMPLIFIED SOLUTION THAT IS NOT WELL-SUPPORTED BY THE LATEST DETERMINISTIC GUIDANCE AND THE 09Z SREF. BY WED THE 00Z ECMWF MOVES TO THE FAST SIDE OF THE DETERMINISTIC GUIDANCE...BUT IS WELL-SUPPORTED BY ITS ENSEMBLE MEAN. TO ADDRESS THE UNCERTAINTY...A COMPROMISE WITH THE SLOWER GFS IS RECOMMENDED. SHORTWAVE TROUGHS SPILLING OVER THE WESTERN RIDGE INTO THE NORTHERN PLAINS-UPPER MIDWEST TO THE OH AND TN VALLEYS ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GFS/00Z ECMWF COMPROMISE CONFIDENCE: AVERAGE FROM LATE TUE TO LATE WED...THE NAM APPEARS TO BE A RELATIVE OUTLIER HERE AS WELL...CARVING OUT LOWER HEIGHTS THAN THE MODEL CONSENSUS FROM THE LOWER MO TO THE LOWER OH AND TN VALLEYS. OVERALL THE GFS/00Z ECMWF ARE IN FAIRLY GOOD AGREEMENT THROUGH LATE WED. ON THU THE NAM IS ALONE IS DIGGING THE SHORTWAVE THAT SLIDES OUT OF SOUTHERN ALB/SASK FURTHER TO THE SOUTHWEST INTO THE NORTHERN/CENTRAL HIGH PLAINS. IN CONTRAST...BY LATE THU THE 00Z ECWMF IS WELL TO THE EAST ACROSS THE UPPER MIDWEST WITH THIS SYSTEM...BUT AGAIN IT IS WELL-SUPPORTED BY ITS ENSEMBLE MEAN...MAKING IT DIFFICULT TO DISCOUNT COMPLETELY. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... PEREIRA