MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1212 AM EDT WED JUL 08 2015 VALID JUL 08/0000 UTC THRU JUL 11/1200 UTC ..SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 00Z MODEL EVALUATION...INCLUDING THE NAM AND GFS ...SHORTWAVE/FRONT CROSSING NORTHERN NEW ENGLAND THROUGH WED... ...ASSOCIATED SURFACE WAVE CROSSING THE NORTHERN MID-ATLANTIC... PREFERENCE: GENERAL MODEL COMPROMISE CONFIDENCE: ABOVE AVERAGE THE MODELS TAKE THE SOUTHERN PORTION OF A NORTHERN STREAM TROUGH ACROSS NORTHERN NEW ENGLAND THROUGH WED ALONG WITH WITH AN ASSOCIATED COLD FRONT. THE SOUTHERN TAIL OF THIS FRONT WILL DRAPE BACK ACROSS THE NORTHERN MID-ATLANTIC AND OH VALLEY WHERE IT WILL BE SLOWING DOWN AND STALLING OUT. THE GUIDANCE SUPPORTS A WEAK WAVE OF LOW PRESSURE MOVING ALONG THE FRONT AND CROSSING THE NORTHERN MID-ATLANTIC LATE WED BEFORE THEN MOVING OFFSHORE. THERE IS RATHER MINIMAL SPREAD WITH THE MODEL MASS FIELDS...AND SO A GENERAL MODEL COMPROMISE WILL BE PREFERRED AT THIS POINT WITH THIS SYSTEM. ...SHORTWAVE OVER OK/TX LIFTING NORTHEAST AND SHEARING INTO THE OH VALLEY... ...DEVELOPING SURFACE LOW LIFTING THROUGH THE MID MS/OH VALLEYS AND MID-ATLANTIC... PREFERENCE: BLEND OF THE 00Z GFS AND 12Z ECMWF CONFIDENCE: SLIGHTLY ABOVE AVERAGE A MID LEVEL SHORTWAVE TROUGH CURRENTLY LIFTING NORTHEAST ACROSS THE RED RIVER VALLEY OF OK/TX WILL LIFTING NORTHEAST AND THEN SHEAR EAST AROUND THE NORTH SIDE OF A DEVELOPING RIDGE AXIS ACROSS THE GULF COAST STATES. THE ENERGY WILL BE ACCOMPANIED BY A WAVE OF LOW PRESSURE THAT WILL LIFT THROUGH THE MID MS/OH VALLEYS THROUGH WED...AND THEN THE MID-ATLANTIC ON THURS. THERE IS REASONABLY GOOD MODEL AGREEMENT ALOFT WITH THE SHORTWAVE DETAILS...BUT AT THE SURFACE...THE 12Z CMC WAS A TAD SLOWER WITH THE WAVE EVOLUTION AND THE 12Z UKMET WAS A TAD FASTER. THE 00Z NAM/00Z GFS AND 12Z ECMWF SPLIT THE DIFFERENCE. THE STRONGER MODEL CLUSTERING OVERALL FAVORS A BLEND OF THE 00Z GFS AND 12Z ECMWF AND HAS STRONGER ENSEMBLE SUPPORT. ...ADDITIONAL SHORTWAVE DIGGING INTO THE CENTRAL/SOUTHERN HIGH PLAINS... PREFERENCE: BLEND OF THE 12Z ECMWF/12Z CMC AND 12Z ECMWF CONFIDENCE: SLIGHTLY BELOW AVERAGE THE MODELS SHOW ADDITIONAL SHORTWAVE ENERGY TRAVERSING THE FOUR CORNERS REGION AND DIGGING OUT INTO THE CENTRAL/SOUTHERN HUGH PLAINS WED AND THURS. THE GUIDANCE INDICATES THIS ENERGY LIFTING NORTHWARD TOWARD THE NORTHERN PLAINS AHEAD OF THE STRENGTHENING HEIGHT FALLS OVER THE INTERMOUNTAIN WEST THROUGH FRI. THE 00Z NAM AND 00Z GFS ARE STRONGER WITH THE MID LEVEL SHORTWAVE AND ACTUALLY SUGGEST POSSIBLY A WEAK WAVE OF LOW PRESSURE ADVANCING NORTH THROUGH THE PLAINS AS A WARM FRONT ALSO LIFTS NORTH. THE 12Z ECMWF/12Z CMC AND 12Z UKMET ARE WEAKER WITH THE ENERGY AND SURFACE REFLECTION. THE GEFS AND ECENS MEMBERS ARE OVERALL NOT AS EMPHATIC ON A STRONGER SHORTWAVE LIFTING NORTH AND SHOW LITTLE SUPPORT FOR A DISCRETE NORTHWARD MOVING SURFACE LOW. WILL FAVOR A NON-NCEP CONSENSUS LED BY THE 12Z ECMWF/12Z UKMET AND 12Z CMC. ...EASTERN PACIFIC UPPER LOW MOVING INTO CALIFORNIA... ...TROUGH LIFTING THROUGH THE CENTRAL/NORTHERN GREAT BASIN... PREFERENCE: NON-CMC CONSENSUS CONFERENCE: ABOVE AVERAGE ALL OF THE LATEST DETERMINISTIC GUIDANCE TAKES AN UPPER LOW OFF THE WEST COAST OF CALIFORNIA EASTWARD AND THROUGH CALIFORNIA LATE WED AND THURS. THE UPPER LOW IS THEN EXPECTED TO OPEN UP INTO A LARGER SCALE UPPER TROUGH THAT WILL MOVE THROUGH THE CENTRAL AND NORTHERN GREAT BASIN ON FRI IN RESPONSE TO ADDITIONAL UPSTREAM HEIGHT FALLS APPROACHING THE WEST COAST. THE 12Z CMC GRADUALLY BECOMES A BIT MORE PROGRESSIVE ENERGY AS IT MOVES INLAND BUT ALSO HANGS ON TO A SOMEWHAT STRONGER TROUGH VERSUS THE MULTI-MODEL CONSENSUS. THE HEIGHT FALLS WILL FAVOR A LOWERING OF SURFACE PRESSURES OVER THE NORTHERN HIGH PLAINS FRI AND SAT FOR WHICH THERE IS RATHER GOOD MODEL AGREEMENT. A NON-CMC CONSENSUS WILL BE PREFERRED. ...UPPER TROUGH APPROACHING THE NORTHWEST ON SAT... PREFERENCE: NON-ECMWF CONSENSUS CONFIDENCE: AVERAGE THE MODELS SHOW ADDITIONAL LARGE SCALE HEIGHT FALLS DIGGING TOWARD THE NORTHWEST BY THIS WEEKEND. THE 12Z ECMWF AND THE 12Z ECENS MEAN ARE A BIT WEAKER WITH THE HEIGHT FALLS VERSUS THE GLOBAL MODEL CONSENSUS AS THE ECMWF WANTS TO FOCUS MORE ENERGY BACK TO THE NORTHWEST OVER THE GULF OF AK. THE 00Z NAM/00Z GFS/12Z UKMET AND 12Z CMC ALL HAVE A STRONGER TROUGH AT LEAST DIGGING TOWARD THE NORTHWEST BY SAT. BASED ON THIS CLUSTERING...A NON-ECMWF CONSENSUS WILL BE PREFERRED. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... ORRISON