MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1134 PM EST FRI FEB 19 2016 VALID FEB 20/0000 UTC THRU FEB 23/1200 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 00Z NAM/GFS EVALUATION INCLUDING INITIAL MODEL PREFERENCES AND FORECAST CONFIDENCE ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ SHORT WAVES CROSSING THE GREAT LAKES INTO NEW ENGLAND SAT ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GENERAL MODEL BLEND CONFIDENCE: ABOVE AVERAGE BOTH THE 00Z NAM/GFS WERE CLOSE TO EACH OTHER (AND THE MODEL CONSENSUS) WITH THE SHORT WAVES AS THEY TRACK FROM THE GREAT LAKES EARLY ON DAY 1 INTO NEW ENGLAND. SHORT WAVE OVER THE PACIFIC NORTHWEST EARLY SAT CROSSING THE OH VALLEY SUN. SURFACE WAVES FORMING ALONG A FRONTAL BOUNDARY STRETCHING FROM THE SOUTHERN PLAINS TO THE MID ATLANTIC SUN INTO MON ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 00Z GFS/12Z ECMWF BLEND CONFIDENCE: AVERAGE ONCE AGAIN...THE DEPTH OF THE UPSTREAM LONG WAVE TROUGH NEAR 36N 150W WILL DICTATE JUST HOW QUICKLY THE SHORT WAVE CROSSES THE PACIFIC NORTHWEST DURING DAY 1 INTO EARLY DAY 2. THE 12/18Z ENSEMBLE SOLUTIONS SUPPORT A BLEND OF THE 00Z GFS/12Z ECMWF...AS THE 00Z NAM IS FASTER AND FLATTER WITH THE SHORT WAVE (WHICH IS MIRRORED BY THE 21Z SREF MEAN). BOTH THE 12Z UKMET/CMC ARE FLATTER AND FASTER WITH THE SHORT WAVE. BROAD LONG WAVE TROUGH CROSSING THE BAJA SAT AND FOUR CORNERS/TX SUN INTO MON ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 00Z GFS/12Z ECMWF BLEND CONFIDENCE: AVERAGE BOTH THE 00Z NAM/GFS ARE CLOSE TO THE CONSENSUS POSITION OF THE BROAD LONG WAVE TROUGH AS IT CROSSES THE BAJA PENINSULA DURING DAY 1. HOWEVER... DIFFERENCES START TO BECOME MORE NOTICEABLE DURING DAY 2...AS SHORT WAVE ENERGY FROM THE PACIFIC NORTHWEST DROPS INTO THE BASE OF THE LONG WAVE TROUGH OVER NM/TX DURING LATE DAY 2 INTO DAY 3. THE 00Z NAM APPEARS TO BE TOO PROGRESSIVE WITH THE LONG WAVE TROUGH...AS IT REACHES A POSITION FROM THE CENTRAL PLAINS INTO EAST TX (WHICH IS VERY CLOSER TO THE FAST 12Z UKMET). THERE IS 12Z ECMWF ENSEMBLE/18Z GEFS SUPPORT FOR THE LONG WAVE TROUGH TO REMAINS FURTHER WEST ACROSS THE FOUR CORNERS INTO TX...WHICH IS CLOSE TO A 00Z GFS/12Z ECMWF BLEND POSITION. THIS WOULD ALSO SUPPORT A SURFACE LOW POSITION OVER THIS REGION ON DAY 3...AS WELL AS A SURFACE WAVE ON A FRONTAL BOUNDARY ACROSS THE GULF COAST STATES. THE 00Z GFS/12Z ECMWF BLEND SUPPORTS THESE IDEAS...SO THIS BLEND IS RECOMMENDED. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... HAYES