MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1217 AM EDT WED AUG 05 2015 VALID AUG 05/0000 UTC THRU AUG 08/1200 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 00Z NAM/GFS EVALUATION WITH PRELIMINARY MODEL PREFERENCES ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ NAM/GFS INITIALIZATION ERRORS DO NOT APPEAR TO DEGRADE THEIR SHORT RANGE FORECASTS. CLOSED LOW MOVING INTO THE WEST FRIDAY DEEP CYCLONE APPROACHING HAIDA GWAII LATE FRIDAY ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GENERAL MODEL COMPROMISE CONFIDENCE: ABOVE AVERAGE THE GUIDANCE REMAINS IN GOOD AGREEMENT WITH THESE SYSTEMS. POSSIBLE CLOSED LOW NEAR THE CENTRAL US/CAN BORDER FRI PRECEDING SHORTWAVE MOVING INTO LAKE SUPERIOR FRI NIGHT ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: CLOSE TO THE CANADIAN CONFIDENCE: BELOW AVERAGE THE GUIDANCE SHOWS CONSIDERABLE SPREAD WITH THIS SYSTEM. THE 00Z GFS IS THE MOST NORTHERLY WHILE THE 12Z UKMET IS THE MOST SOUTHERLY AND ONE OF THE STRONGER SOLUTIONS WITH THE SHORTWAVE KICKING OUT AHEAD OF IT. THE 12Z ECMWF RESEMBLED THE 12Z UKMET AT THE SURFACE WITH THE DEPTH OF THE WAVE MOVING INTO LAKE SUPERIOR EARLY SATURDAY, WHICH WAS PROBLEMATIC. ANY SYSTEMS MOVING OVER THE TOP OF THE SLOWLY AMPLIFYING RIDGE IN THE SOUTHERN PLAINS SHOULD NOT BE OVERLY STRONG MOVING OVER ITS APEX DUE TO SUPERGEOSTROPHIC/QUICK FLOW, WHICH RULES OUT THE UKMET/ECMWF FROM CONSIDERATION. THE 12Z GLOBAL ENSEMBLE GUIDANCE FAVORED A SOLUTION CLOSE TO THE 12Z CANADIAN, WHICH IS PREFERRED WITH BELOW AVERAGE CONFIDENCE. EASTERN TROUGH SURFACE LOW NEAR THE EAST COAST SATURDAY MORNING ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: CLOSE TO THE NAM CONFIDENCE: AVERAGE THE 12Z UKMET WAS WEAKER THAN THE OTHER GUIDANCE WITH THIS TROUGH -- ONE OF ITS USUAL BIASES. BOTH THE 12Z CANADIAN/12Z UKMET APPEAR TO GENERATE A CONVECTIVE WAVE WHICH DEEPENS AS IT PASSES THE 40N 70W BENCHMARK -- THEIR USUAL BIAS. OTHERWISE, THE 12Z GLOBAL ENSEMBLE GUIDANCE IS SPREAD BETWEEN THE NORTHERLY 12Z ECMWF (WHICH SOMETIMES HAS THIS BIAS THREE DAYS INTO THE FUTURE WITH COASTAL LOWS) AND THE SOUTHERLY 00Z GFS. A COMPROMISE OF THE TWO, NOT FAR FROM THE 00Z NAM, APPEARS BEST WITH AVERAGE CONFIDENCE. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... ROTH