MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 150 AM EST WED FEB 04 2015 VALID FEB 04/0000 UTC THRU FEB 07/1200 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... ...AN EVALUATION OF THE 00Z MODEL GUIDANCE ALONG WITH FINAL PREFERENCES/FORECAST CONFIDENCE... THERE DID NOT APPEAR TO BE ANY INITIALIZATION ERRORS WITH THE 00Z NAM/GFS DEEMED SIGNIFICANT ENOUGH TO IMPACT THEIR FORECASTS. ...INITIAL CLOSED LOW CROSSING THE RIO GRANDE... ...OPEN WAVE TRACKING ALONG THE GULF COAST THROUGH EARLY THURSDAY... FINAL PREFERENCE: 00Z ECMWF FORECAST CONFIDENCE: SLIGHTLY ABOVE AVERAGE WATER VAPOR IMAGERY SHOWED A COMPACT CYCLONIC CIRCULATION MOVING TOWARD THE RIO GRANDE WITH ENHANCED MOISTURE LIFTING AHEAD OF IT TOWARD THE WESTERN/CENTRAL GULF COASTS. THIS SYSTEM QUICKLY BECOMES MORE OF AN OPEN WAVE AS IT MARCHES EASTWARD ALONG THE GULF COAST REGION. REGARDING THE MODELS...SOME OF THE 00Z MODELS MADE SOME MINOR ADJUSTMENTS WITH THE 00Z UKMET SLOWING A TAD DOWN WHILE THE 00Z CMC ON THE WESTERN SIDE OF THE SPREAD. WHEN IT IS ALL SAID AND DONE...THE 00Z NAM/UKMET SIT ON THE SLIGHTLY FASTER END OF THE SPECTRUM WHILE THE 00Z GFS/CMC ARE SLOWER. WILL LEAN ON THE MIDDLE OF THE ROAD 00Z ECMWF SOLUTION. ...AMPLIFIED TROF TRACKING FROM THE UPPER MIDWEST TO NEW ENGLAND ON WEDNESDAY/THURSDAY... ...ADVANCING BAROCLINIC ZONE/WAVES OF LOW PRESSURE... FINAL PREFERENCE: BLEND OF THE 00Z NAM/UKMET FORECAST CONFIDENCE: BELOW AVERAGE A PROGRESSIVE AXIS OF HEIGHT FALLS CURRENTLY MOVING TOWARD SOUTHERN MANITOBA WILL TRACK FROM THE UPPER MIDWEST TO NEW ENGLAND THROUGH LATE THURSDAY NIGHT. UNLIKE THE PRECEDING FEW RUNS OF THE ECMWF SUITE WHICH HAD BEEN SLOWER AND MORE AMPLIFIED...THIS 00Z ECMWF/12Z ECMWF ENSEMBLE MEAN AT LEAST HAVE JOINED THE MORE PROGRESSIVE PACK. AS THE UPPER TROF CROSSES THE UPPER MID-ATLANTIC BY 05/1800Z...THE 00Z CMC/ECMWF HAVE MADE A MOVE IN THE FASTER DIRECTION WHICH PLACES THEM NEAR THE 00Z NAM/GFS/UKMET. HOWEVER...THE 00Z CMC/ECMWF DO END UP ON THE SLOWER SIDE AS THE UPPER TROF BECOMES NEGATIVELY-TILTED AND LIFTS UP THE COASTAL NEW ENGLAND. WILL CONTINUE TO STICK WITH THE PREVIOUS PREFERENCE COMBINING THE 00Z NAM/UKMET AS THE 00Z GFS MAY BE TOO QUICK WHICH HAPPENS TO BE QUICKER THAN ITS 00Z GEFS MEAN. THIS SOLUTION PROVIDES A REASONABLE COMPROMISE WITH THE SURFACE LOW TRACK IN SPITE OF ALL THE MODEL DIFFERENCES. THE FORECAST CONFIDENCE REMAINS BELOW AVERAGE. ...SECONDARY SYSTEM AFFECTING UPPER NEW ENGLAND BY FRIDAY... ...RESULTANT MID-LEVEL VORTEX SETTLING INTO QUEBEC BY THE WEEKEND... FINAL PREFERENCE: 12Z ECMWF ENSEMBLE MEAN FORECAST CONFIDENCE: SLIGHTLY BELOW AVERAGE AS THE INITIAL UPPER TROF AMPLIFIES OVER NEW ENGLAND...A SECONDARY SHORTWAVE IS FORECAST TO DIVE DOWN FROM SOUTH OF HUDSON BAY TOWARD THE INTERIOR NORTHEAST BY FRIDAY. WHILE MODEL SPREAD IS NOT TERRIBLY SIGNIFICANT WITH THE INITIAL IMPULSE APPROACHING NEW ENGLAND...THERE IS GREATER UNCERTAINTY WITH THE PLACEMENT OF A BROAD VORTEX DIPPING DOWN ACROSS QUEBEC. THE 00Z CMC/UKMET DID BOTH MOVE NORTHWARD AWAY FROM THEIR PREVIOUS FORECASTS WHICH DID NOT MATCH ANY OTHER PIECE OF GUIDANCE. IT LOOKS LIKE MOST OF THE DETERMINISTIC SOLUTIONS...AT LEAST AMPLITUDE-WISE...ARE MOVING TOWARD THE 12Z ECMWF ENSEMBLE MEAN. THE FLATTER 00Z GEFS/21Z SREF MEANS ARE NOT SUPPORTED AS MUCH AT THIS TIME. WILL RECOMMEND THE 12Z ECMWF ENSEMBLE MEAN HERE WHILE SLIGHTLY RAISING CONFIDENCE. ...SERIES OF SHORTWAVES AFFECTING THE PACIFIC NORTHWEST... FINAL PREFERENCE: THROUGH 06/1200Z: BLEND OF THE 00Z NAM/ECMWF...THEREAFTER...A BLEND OF THE 00Z GEFS/21Z SREF/12Z ECMWF ENSEMBLE MEANS FORECAST CONFIDENCE: AVERAGE AN UPPER RIDGE INITIALLY ANCHORING THE WEST COAST WILL BREAK DOWN AND GIVE WAY TO A SERIES OF SHORTWAVES WHICH ARE EXPECTED TO BOMBARD LOCATIONS FROM NORTHERN CA UP TO THE CANADIAN BORDER. THE FIRST SIGNIFICANT WAVE APPROACHING THE PACIFIC NORTHWEST ON THURSDAY WILL BE THE FIRST OF MANY WHICH CARRY A HEAVY RAINFALL THREAT TO MUCH OF THIS REGION. THE 12Z CMC APPEARS SLOWER TO CARRY THESE INITIAL HEIGHT FALLS TOWARD THE COASTLINE. GIVEN THE SIMILARITIES OF THE MODELS EXCEPT FOR THE 00Z CMC THROUGH DAY 2...WILL SUGGEST A FOCUS ON THE HIGHER RESOLUTION MODELS GIVEN THEIR HANDLING OF THE COMPLEX TERRAIN OUT WEST. THAT IS...A BLEND OF THE 00Z NAM/ECMWF THROUGH 06/1200Z. THERE IS MUCH MORE SPREAD LATE IN THE PERIOD WITH THE TIMING OF AN AMPLIFIED WAVE APPROACHING THE CA/OR BORDER LATE FRIDAY/EARLY SATURDAY. THERE WERE NO DEFINITIVE TRENDED SEEN IN THE 00Z GUIDANCE SO WILL STAY THE COURSE WITH AN ENSEMBLE MEANS BLEND. REGARDLESS OF THE PREFERENCE...THE HEAVY RAINFALL SIGNAL CONTINUES INTO DAY 3...PARTICULARLY OVER THE SHASTA RANGE. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... RUBIN-OSTER