MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1254 PM EDT FRI APR 07 2017 VALID APR 07/1200 UTC THRU APR 11/0000 UTC VALID APR 07/1200 UTC THRU APR 11/0000 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 12Z INITIAL MODEL PREFERENCES ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ NO SIGNIFICANT NAM/GFS INITIALIZATION ERRORS WERE NOTED IN AND NEAR NORTH AMERICA. ...DEEP CYCLONE DEPARTING NEW ENGLAND LATE TODAY AND TONIGHT... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GENERAL MODEL BLEND CONFIDENCE: ABOVE AVERAGE MODELS HANDLE THIS SYSTEM SIMILARLY...WITH PERHAPS A PREFERENCE FOR THE SLIGHTLY SLOWER 00Z ECMWF AND 00Z ECMWF ENSEMBLE MEAN SOLUTION AT 60 HOURS AND BEYOND SINCE THERE IS NO SIGNIFICANT KICKER SEEN UPSTREAM. ...DEEP CYCLONE MOVING NORTH OVER OFFSHORE WATERS OF THE NORTHWEST TODAY AND ONTO BRITISH COLUMBIA COAST LATE TONIGHT AND SAT MORNING... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: MODEL BLEND THAT EXCLUDES THE NAM CONFIDENCE: SLIGHTLY ABOVE AVERAGE THE 12Z NAM AND GFS ARE SIMILARLY WELL INITIALIZED. HOWEVER WITHIN 18 HOURS...BY 06Z SAT...THE NAM SURFACE SOLUTION IS AN OUTLIER. THE NAM TAKES THE SURFACE LOW ACROSS THE CENTER OF VANCOUVER ISLAND...WHEREAS ALL OTHER MODEL SOLUTIONS TRACK THE LOW ACROSS THE NORTHERN TIP OF VANCOUVER ISLAND - OR EVEN A LITTLE FURTHER WEST. CLIMATOLOGY FAVORS A TRACK THAT IS DUE NORTH OR EVEN SLIGHTLY WEST OF DUE NORTH. THE LOW JUST OFF KODIAK ISLAND SHOULD HELP THAT...AND THE LOW APPEARS TO BE TURNING MORE TO THE NORTH IN RECENT SATELLITE IMAGERY. ...SYSTEM MOVING INTO CALIFORNIA TONIGHT AND SAT MORNING...CROSSING THE ROCKY MOUNTAINS SAT NIGHT...AND MOVING ACROSS THE PLAINS LATE SUN THRU MON... ...WEAK SURFACE LOW NEARING CNTRL CALIFORNIA COAST THIS EVENING... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GENERAL MODEL BLEND...EXCLUDING THE NAM SURFACE SOLUTION DURING THE FIRST 24 HOURS CONFIDENCE: SLIGHTLY BELOW AVERAGE THE INITIAL FEATURE TO AFFECT CALIFORNIA WILL BE THE DEVELOPING SHORTWAVE/SMALL BAROCLININC LEAF CURRENTLY CROSSING 130W. THE NAM APPEARS TO HAVE TOO ROBUST OF AN INITIALIZATION OF THIS FEATURE AND CONSEQUENTLY DEEPENS THE SURFACE LOW EXCESSIVELY. OTHERWISE THE NAM AND GFS - AS WELL AS THE 00Z SUITE OF MODELS AND ENSEMBLE MEANS - HANDLE THE DOWNSTREAM PROGRESSION OF THIS SYSTEM SIMILARLY. ...UPPER TROUGH/SURFACE COLD FRONT REACHING THE PACIFIC NORTHWEST LATE SUN/SUN NIGHT... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GFS AND NAM COMPROMISE CONFIDENCE: AVERAGE THE NAM AND GFS SHOW DEEPER DEVELOPMENT AND QUICKER PROGRESSION WITH THIS SYSTEM THAN THE 00Z SUITE OF MODELS AND ENSEMBLE MEANS. HOWEVER, SOME OF THE ECMWF ENSEMBLES AGREE WITH A STRONGER SYSTEM. THIS IS NOT AN UNREASONABLE DEVELOPMENT GIVEN THE RETROGRADING RIDGE OVER WESTERN CANADA AND UNDERCUTTING ENERGY. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... MCDONNAL/ROTH