MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 240 PM EDT FRI JUL 25 2014 VALID JUL 25/1200 UTC THRU JUL 29/0000 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... ...AN EVALUATION OF THE 12Z CMC/UKMET/ECMWF ALONG WITH FINAL PREFERENCES/FORECAST CONFIDENCE... THERE DID NOT APPEAR TO BE ANY INITIALIZATION ERRORS WITH THE 12Z NAM/GFS DEEMED SIGNIFICANT ENOUGH TO IMPACT THEIR FORECASTS. ...SURFACE LOW TRACKING FROM THE NORTHERN/CENTRAL PLAINS TO THE MIDDLE MS VALLEY THROUGH 26/1200Z... FINAL PREFERENCE: 12Z NAM/GFS FORECAST CONFIDENCE: AVERAGE THIS SURFACE FEATURE IS ASSOCIATED WITH A BAROCLINIC ZONE ATTEMPTING TO REDEVELOP EASTWARD AHEAD OF THE INCREASING MID LEVEL WESTERLY FLOW ARRIVING FROM THE NORTHERN PLAINS AND PRAIRIE PROVINCES. THE NAM AND GFS BOTH TRENDED FASTER IN MOVING THE UPPER LOW ALONG THE BORDER WITH CANADA IN THE NEAR TERM. GIVEN HEALTHY SUPPORT FROM 00Z GEFS MEMBERS AND PLACEMENT OF THE SYSTEM WITHIN THE UPPER AIR NETWORK...THIS TREND WILL LIKELY STICK. THE 12Z NAM/GFS/UKMET SHOW FAIR AGREEMENT IN THE PRECIPITATION FIELD...WITH CONVECTIVE PRECIPITATION SWATHS EXPECTED IN THE 700 WARM ADVECTION PEAK OVER MI...850 MB PEAK OVER IL/IN...AND A NEW SWATH GENERATING BENEATH A SHARP MID LEVEL SHORTWAVE OVER SD BY SATURDAY MORNING. THE MORE GENEROUS UKMET OUTPUT MAY BE PREFERRED OVER MI. THESE MODELS ALSO AGREE CLOSELY AT THE SURFACE. ...ANOMALOUS CLOSED LOW DROPPING FROM SOUTHERN SASKATCHEWAN INTO THE UPPER GREAT LAKES... ...WELL-DEFINED COLD FRONT... FINAL PREFERENCE: BLEND OF THE 12Z ECMWF/UKMET FORECAST CONFIDENCE: SLIGHTLY BELOW AVERAGE AS MENTIONED ABOVE...THERE IS A TREND TOWARD QUICKER PROGRESSION OF THIS LOW IN THE 12Z NCEP GUIDANCE. THE 12Z/00Z UKMET...ALTHOUGH SLOWER ALOFT...SHOWS RELATIVE AGREEMENT WITH THE NAM/GFS AT THE SURFACE AND IN THEIR PRECIPITATION OUTPUT. MOVING INTO DAY 2...THE MODEL SPREAD CONTINUES TO BUILD WITH THE 12Z NAM/GFS AND 12Z GEFS/09Z SREF MEANS BEING MORE PROGRESSIVE THAN THE NON-NCEP GUIDANCE. THE TIMING OF THE STRONG MID/UPPER WINDS WITH THE PASSAGE OF THIS ROBUST SHORTWAVE WILL BE CRITICAL TO THE FORECAST GIVEN THE HIGHER END IMPACTS OF HEAVY RAINFALL AND SEVERE WEATHER POSSIBLE. THE DIFFERENCES BETWEEN THE TWO CAMPS HAS DIMINISHED A BIT AFTER EVALUATING ALL OF THE AVAILABLE 12Z GUIDANCE. THE 12Z ECMWF HAS DEFINITELY SPED UP LEAVING THE 00Z ECMWF ENSEMBLE MEAN AS THE SLOWEST PIECE OF GUIDANCE. WILL STICK WITH THE PREVIOUS PREFERENCE WHILE UTILIZING THE 12Z VERSION OF EACH. CONFIDENCE WILL BE RAISED SLIGHTLY GIVEN THE MODEL DIFFERENCES HAVE DIMINISHED. ...MEAN TROF ANCHORING NORTHEASTERN NORTH AMERICA... FINAL PREFERENCE: BLEND OF THE 12Z ECMWF/UKMET FORECAST CONFIDENCE: AVERAGE A VERY ANOMALOUS HEIGHT PATTERN EVOLVES ACROSS MUCH OF THE EASTERN THIRD OF THE COUNTRY WITH MODELS INDICATING 500-MB HEIGHTS MAY BE AT LEAST 3 STANDARD DEVIATIONS BELOW CLIMATOLOGY FOR LATE JULY. WHILE ALL GUIDANCE INDICATE THE PRESENCE OF THIS LONGWAVE TROF...THEY DO VARY WITH THE DETAILS. MUCH OF THESE DIFFERENCES ARE A RESULT OF THE TIMING OF THE AFOREMENTIONED SHORTWAVE DIGGING THROUGH THE UPPER GREAT LAKES ON SATURDAY/SUNDAY. WILL MAINTAIN THE SAME PREFERENCE AS THE PREVIOUS SECTION. GIVEN THE MODELS AGREE ON THE SYNOPTIC PATTERN HERE...FEEL COMFORTABLE KEEPING THE CONFIDENCE AT AVERAGE. ...SHORTWAVE APPROACHING NORTHERN CA BY SUNDAY... FINAL PREFERENCE: 12Z NAM/UKMET/ECMWF FORECAST CONFIDENCE: SLIGHTLY ABOVE AVERAGE ALONG THE WESTERN PERIPHERY OF AN EXPANSIVE MID/UPPER LEVEL RIDGE ACROSS THE FOUR CORNERS/SOUTHERN PLAINS...A SHORTWAVE IS EXPECTED TO APPROACH THE NORTHERN CA COAST EARLY SUNDAY. OVERALL...THE 12Z NAM/ECMWF/UKMET FOLLOW THE WELL CLUSTERED ENSEMBLE MEANS MOST CLOSELY. WITH THAT BEING THE CASE...ANY FORM OF COMBINATION OF THE 12Z NAM/ECMWF/UKMET SHOULD SUFFICE. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... RUBIN-OSTER/BURKE