MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 247 PM EDT SUN MAY 11 2014 VALID MAY 11/1200 UTC THRU MAY 15/0000 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... ============================================== 12Z MODEL EVALUATION AND PREFERENCES ============================================== NAM/GFS INITIALIZATION ERRORS DO NOT APPEAR TO SIGNIFICANTLY AFFECT THEIR LARGE SCALE OUTPUT. ============================================== ...PLAINS/MIDWEST CYCLONE AND TRAILING COLD FRONT... PREFERENCE: BLEND OF 12Z GFS/ECMWF CONFIDENCE: AVERAGE INTERACTION BETWEEN A SHORTWAVE EJECTING FROM THE ROCKIES AND A TROUGH ENTERING THE DAKOTAS WILL YIELD A BETTER DEFINED NORTHERN STREAM TROUGH AND ASSOCIATED LOW LEVEL CYCLONE LIFTING THROUGH THE UPPER MIDWEST. THE GLOBAL MODELS HAVE TRENDED TOGETHER ON THIS FEATURE...AND SHOW VERY LITTLE DIFFERENCE AT THE SURFACE. THE GFS/ECMWF ARE PREFERRED FOR THEIR HANDLING OF THE MID LEVELS...WHEREAS THE 12Z UKMET IS SOMEWHAT WEAK IN THE TROUGH AND MISSES THE AMPLITUDE OF THE DOWNSTREAM RIDGE. THE CANADIAN CONTINUED WITH A SOLUTION THAT IS SLOWER TO ADVANCE THE MID LEVEL TROUGH AND ASSOCIATED COLD AIR. THE NAM IS MORE OF AN OUTLIER BEGINNING EARLY IN THE PERIOD. IT STRONGLY EMPHASIZES THE ROCKIES SHORTWAVE AND UNDER-EMPHASIZES THE DAKOTAS TROUGH. THE LATTER SHOULD SERVE TO ELONGATE/PHASE THE UPPER ENERGY. THE NAM PRODUCES A MORE ROBUST SURFACE CYCLONE TRACKING FARTHER NORTH AND WEST. ...EXTENSION OF THE UPPER TROUGH INTO THE SOUTHERN TIER OF STATES... ...CYCLOGENESIS INITIATING ALONG THE FRONT ON DAY 3 NEAR TENNESSEE/KENTUCKY... PREFERENCE: 12Z ECMWF CONFIDENCE: AVERAGE AT THIS LATITUDE THE ECMWF/ECMWF ENSEMBLE MEAN HAVE BEEN PREFERRED FOR SEVERAL CYCLES. THE 00Z ECMWF TRENDED TOWARD THE DEEP AND PROGRESSIVE SIDE...SLINGING THE SOUTHERN PORTION OF THE TROUGH INTO A NEGATIVE TILT. THIS MAY HAVE BEEN IN PART DUE TO CONVECTIVE FEEDBACK...BUT ALSO FORCED BY A DEEPER NORTHERN STREAM TROUGH ACTING TO KICK THE SOUTHERN STREAM. THE 12Z ECMWF TRENDED TOWARD OUR PREFERRED SOLUTION IN BOTH RESPECTS...LOSING THE FEEDBACK AND LESSENING INTERACTION WITH THE NORTHERN STREAM. THE 12Z ECMWF FITS OUR CONCEPTUAL MODEL AT THE SURFACE AND ALOFT...SO WE DROPPED THE GFS FROM OUR PREFERENCE HERE. THE 12Z GFS LARGELY SUPPORTS OUR CONCEPT...BUT IS SOMEWHAT WEAKER ALOFT AND LACKS A CLOSED CONTOUR AT THE SURFACE ON DAY 3. THE NAM...CANADIAN...AND UKMET DISPLAY SLOWER AND DEEPER SOLUTIONS. THIS IDEA HAS BEEN MORE PERSISTENT IN THE CANADIAN...BUT SPAGHETTI PLOTS HAVE SHOWN IT TO BE A SLOW/DEEP OUTLIER FOR SEVERAL CONSECUTIVE CYCLES. ALTHOUGH A DEEPER SOLUTION CANNOT BE RULED OUT...THERE IS MUCH MORE ENSEMBLE SUPPORT FOR THE ECMWF...AND RUN TO RUN CONSISTENCY IN THE NAM/UKMET HAS BEEN POOR. ...NORTHEASTERN U.S SHORTWAVE TODAY/MONDAY... PREFERENCE: NONE CONFIDENCE: ABOVE AVERAGE MODELS HANDLE THIS LOW AMPLITUDE WAVE SIMILARLY...INCLUDING THE POSITION AT WHICH A BACKDOOR COLD FRONT STALLS OVER THE MID ATLANTIC BY DAY 3. ANY LARGE SCALE DIFFERENCES APPEAR TO OCCUR WELL OFFSHORE. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... BURKE