MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1248 AM EDT TUE MAY 20 2014 VALID MAY 20/0000 UTC THRU MAY 23/1200 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... ================================================== 00Z NAM/GFS EVALUATION AND PRELIMINARY PREFERENCES ================================================== NAM/GFS INITIALIZATION ERRORS DO NOT APPEAR TO SIGNIFICANTLY AFFECT THEIR LARGE SCALE OUTPUT. ================================================== ...DEEP TROUGH SETTLING INTO THE SOUTHWEST STATES... PREFERENCE: BLEND OF 00Z GFS WITH 12Z ECMWF/CANADIAN BROAD AGREEMENT CONTINUES...WITH MINOR VARIATIONS FROM RUN TO RUN. THE GFS/ECMWF/CANADIAN NOW CLUSTER VERY WELL...WHEREAS THE 12Z GFS HAD BEEN POSITIONED SLIGHTLY NORTH AND EAST OF CONSENSUS DURING THE DAY 1/2 PERIOD. THE 00Z NAM DOES CONTINUE TO SLIDE A LITTLE NORTH AND EAST OF CONSENSUS...AND THE 12Z UKMET WAS OPPOSITE THE NAM AND LOCATED ON THE SOUTHWEST SIDE OF THE SPREAD. SPAGHETTI PLOTS SHOWED THE 12Z UKMET TO BE SOMEWHAT AN OUTLIER WITH NO INVERTED TROUGH STRUCTURE EXTENDING NORTHWARD THROUGH NEVADA ON DAYS 2/3. DESPITE THIS DETAIL...THERE ARE NO STRONG OUTLIERS ON THE LARGE SCALE. THE GFS/ECMWF/CANADIAN CLUSTER IS BEST SUPPORTED BY ENSEMBLE INFORMATION AND CONTINUITY. ...TROUGH PUSHING INTO THE PACIFIC NORTHWEST THURSDAY... PREFERENCE: BLEND OF THE OPERATIONAL MODELS...EXCLUDING THE 12Z CANADIAN THIS SYSTEM MAY JUST BRING SOME LIGHT PRECIPITATION TO NORTHWEST WASHINGTON BY THE END OF THE SHORT RANGE PERIOD...THURSDAY MORNING. ASIDE FROM THE 12Z CANADIAN...WHICH WAS A BIT FAST WITH THE LEAD SHORTWAVE TROUGH...THERE IS GENERAL MODEL CONSENSUS. THE GFS AND ECMWF INDICATE A MORE PRONOUNCED SHORTWAVE THAN THE NAM/UKMET...BUT WITH MOST OF ITS EFFECTS CONCENTRATED TOWARD BRITISH COLUMBIA. DESPITE THE LARGE SCALE AGREEMENT...CONFIDENCE IN THE DETAILS WILL ONLY BE AVERAGE AT THIS 3-DAY LEAD TIME AS THE FLOW PATTERN IS CHARACTERIZED BY LOW AMPLITUDE PERTURBATIONS WITH WESTERLY FLOW AHEAD OF A LARGER SCALE TROUGH. ...SYSTEM CROSSING THE NORTHERN PLAINS TO THE GREAT LAKES AND NORTHEAST STATES... PREFERENCE: BLEND OF 00Z NAM/12Z ECMWF MODEL FORECASTS ARE RELATIVELY SIMILAR HERE...BUT WE FAVOR THE NAM/ECMWF BASED ON A FEW DETAILS. THE 12Z CANADIAN WAS FLAT/WEAK ON DAY 2...AND EVEN MORE-SO ON DAY 3. THE GFS AND UKMET APPEAR TO BE MORE READILY PHASING THE MID LEVEL CENTER WITH ANOTHER TROUGH LIFTING OUT OF THE COASTAL WATERS OFF NEW ENGLAND. THIS PULLS THE GFS/UKMET SOLUTIONS ALONG A LITTLE FASTER AT THE SURFACE AND ALOFT. WE FAVOR THE NAM/ECMWF WHICH MAINTAIN MORE SEPARATION BETWEEN THE TWO FEATURES...AND THEREFORE DIG COOLER HEIGHTS DOWN TO THE MID ATLANTIC BY THURSDAY MORNING. THIS ALSO RESULTS IN A SLIGHTLY SLOWER AND BETTER DEFINED SURFACE REFLECTION. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... BURKE