MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 259 AM EDT SUN SEP 21 2014 VALID SEP 21/0000 UTC THRU SEP 24/1200 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... ============================================== 00Z MODEL EVALUATION AND PREFERENCES ============================================== NAM/GFS INITIALIZATION ERRORS DO NOT APPEAR TO SIGNIFICANTLY AFFECT THEIR LARGE SCALE OUTPUT. ============================================== ...EASTERN U.S...INCLUDING A COASTAL LOW... PREFERENCE DAY 2: BLEND OF 21/00Z NAM/GFS PREFERENCE DAY 3: 21/00Z NAM/GFS AND/OR 20/12Z GEFS MEAN CONFIDENCE: AVERAGE MODELS ARE NOW SIMILAR IN HANDLING THE TRACK AND TIMING OF COASTAL LOW PRESSURE AS IT PARALLELS THE ATLANTIC COAST BEFORE BEING ABSORBED AHEAD OF A SYNOPTIC LOW/FRONT NEAR NEW ENGLAND. THE 21/00Z NAM BACKED AWAY FROM ITS DEEPER SOLN IN HOW IT HANDLES THE TROF OVER THE EASTERN STATES GETTING IT IN BETTER OVERALL AGREEMENT WITH THE GFS AND THE PREVIOUS GEFS MEAN. THE GFS CONTINUITY WAS PRETTY GOOD IN HANDLING THIS FEATURE WHEN COMPARED WITH THE 20/12Z GFS. WHILE THE ECMWF HAD A DIFFERENT TAKE ON THE EAST COAST SYSTEM...ESPECIALLY OVER THE SOUTHEAST ON DAY 3...IT KEPT PRETTY GOOD CONTINUITY WITH ITS PREVIOUS RUN IN THE MID LEVELS. 00Z MODEL RUNS FROM NCEP AND THE UKMET ALONG WITH THE 12Z GEFS WOULD POINT AWAY FROM THE EC IDEA AT THIS POINT...ALTHOUGH THE 00Z CANADIAN LIKES THE IDEA OF A WEAKNESS BETWEEN TWO MID LEVEL HIGHS BUT NOT TO THE ECMWF SOLN. THINK A NON EC SOLN AT THIS POINT IS STILL BEST. ...SHEAR AXIS TRAPPED IN THE UPPER RIDGE BUILDING OVER THE SOUTHERN PLAINS... PREFERENCE: A NON NAM BLEND OF THE OPERATIONAL MODELS CONFIDENCE: AVERAGE OVERALL AGREEMENT IN THE MODEL MASS FIELDS WAS GOOD HERE EXCEPT FOR THE NAM...WHICH BECOMES A BIT OF AN EASTWARD OUTLIER IN TERMS OF WHERE IT PLACES MOISTURE ON DAY 3. ...SYSTEM TRACKING FROM CALIFORNIA TO THE NORTHERN PLAINS... PREFERENCE: ANY OF THE OPERATIONAL MODELS CONFIDENCE: ABOVE AVERAGE THE OPERATIONAL MODELS STILL SHOW STRONG AGREEMENT AT THE SURFACE AND ALOFT. ...DEEP TROUGH LEANING INTO THE PACIFIC NORTHWEST... PREFERENCE: ANY OF THE 00Z NCEP/ECMWF/UKMET RUNS...LESS WEIGHT ON THE CANADIAN CONFIDENCE: ABOVE AVERAGE A LEAD SHORTWAVE WILL BRING HEIGHT FALLS AND THE ONSET OF LIGHT PRECIPITATION WEST OF THE WA/OR CASCADES ON MONDAY. THE WAVE WILL PUSH A WEAK BOUNDARY INTO THE NORTHERN ROCKIES MON/TUE. A DEEPER LONGWAVE TROUGH WILL APPROACH THE COAST BY LATE TUESDAY AND INTO WEDNESDAY. MODEL AGREEMENT IN THE 00Z PRODUCTION CYCLE IS STILL STRONG...ASIDE FROM THE CANADIAN WHICH HAS CONTINUED TO SHOW MORE RUN TO RUN VARIABILITY WITH RESPECT TO SHORTWAVE TIMING AND STRENGTH. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... BANN