MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 254 AM EDT SAT JUL 18 2015 VALID JUL 18/0000 UTC THRU JUL 21/1200 UTC ...CORRECTION FOR PREFERENCE IN FIRST SYSTEM ..SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 00Z MODEL EVALUATION WITH FINAL PREFERENCES ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ NAM/GFS INITIALIZATION ERRORS DO NOT APPEAR TO IMPACT THEIR SHORT TERM FORECASTS. TROPICAL STORM DOLORES ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 00Z NAM/GFS COMPROMISE CONFIDENCE: BY DEFAULT/SEE NHC ADVISORIES THE 03Z NHC TRACK FOR DOLORES BEST MATCHES THE SURFACE LOW TRACK FROM THE 00Z NAM AND 12Z UKMET. HOWEVER...THE UPPER LEVEL REFLECTION OF DOLORES IS WEAKEST/SLOWEST IN THE NAM...WHILE THE 12Z UKMET IS FAST BY MON/TUE ACROSS THE SOUTHWEST...FASTER THAN THE MAJORITY OF ENSEMBLE SPAGHETTI HEIGHT PLOTS. FOR THIS REASON...A BLEND OF THE 00Z NAM/GFS APPEARS BEST AT THIS TIME...WITH AGREEMENT TO THE LATEST NHC ADVISORY...ALTHOUGH THE GFS IS NOTABLY FASTER WITH THE SURFACE LOW TRACK BY MON MORNING. A GENERAL FASTER TREND INTO CALIFORNIA HAS BEEN NOTED IN MANY OF THE 00Z DETERMINISTIC MODELS. SEE THE LATEST NHC ADVISORIES FOR THE LATEST INFORMATION ON DOLORES. SHORTWAVE/FRONT MOVING THROUGH THE GREAT LAKES AND NORTHEAST ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 00Z NAM/00Z ECMWF COMPROMISE CONFIDENCE: AVERAGE THE 00Z GFS WAS FASTER THAN THE MAJORITY OF GUIDANCE WITH THIS SYSTEM...ESPECIALLY BY SUN NIGHT ACROSS THE NORTHEAST. WHILE THE ENSEMBLE MEANS SUPPORT A TIMING CLOSEST TO THE SLOWER 00Z NAM...THE 00Z ECMWF SPED UP AND MATCHES THE 00Z GFS CLOSELY WITH THE PROGRESSION OF THE COLD FRONT THROUGH THE NORTHEAST. IN FACT...MANY OF THE 00Z DETERMINISTIC MODELS SHOW AGREEMENT NOW...BUT THE ENSEMBLES STILL SUPPORT A SOMEWHAT SLOWER PROGRESSION. GIVEN AGREEMENT IN THE TYPICALLY STRONG VERIFICATION OF THE GFS/ECMWF COMBO...AND GIVEN THEY CURRENTLY AGREE...WILL NUDGE IN THEIR GENERAL DIRECTION FROM THE EARLIER PREFERENCE FROM THE 00Z NAM AND 12Z ECMWF. THE 00Z GUIDANCE HAS ALSO TRENDED NORTH WITH THE WESTERN PORTION OF THIS FRONT ACROSS THE PLAINS WHILE THERE REMAINS UNCERTAINTY AND POOR RUN TO RUN CONTINUITY REGARDING A REMNANT SHORTWAVE ON MON...EJECTING EAST FROM THE NORTHWEST. THE PACIFIC NORTHWEST LATE MONDAY ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GENERAL MODEL COMPROMISE CONFIDENCE: SLIGHTLY ABOVE AVERAGE THE GUIDANCE IS IN REASONABLY GOOD AGREEMENT WITH THIS SYSTEM. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... OTTO