MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1150 PM EST TUE FEB 03 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 NAM/GFS ALONG WITH PRELIMINARY 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... PRELIMINARY PREFERENCE: BLEND OF THE 00Z GFS/12Z 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 MODELS...THE 12Z UKMET IS A BIT QUICKER DURING THIS EVOLUTION WHILE OTHER GUIDANCE STAYS A BIT TO THE WEST. MEANWHILE...THE 00Z NAM/12Z ECMWF ARE A HAIR QUICKER THAN THE 00Z GFS/CMC. PLAN ON SPLITTING THE DIFFERENCE BETWEEN THESE TWO SOLUTIONS. WILL FOLLOW A COMBINATION OF THE 00Z GFS/12Z ECMWF AT THIS POINT IN TIME. ...AMPLIFIED TROF TRACKING FROM THE UPPER MIDWEST TO NEW ENGLAND ON WEDNESDAY/THURSDAY... ...ADVANCING BAROCLINIC ZONE/WAVES OF LOW PRESSURE... PRELIMINARY PREFERENCE: BLEND OF THE 00Z NAM/12Z 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 12Z ECMWF/ECMWF ENSEMBLE MEAN AT LEAST HAS JOINED THE MORE PROGRESSIVE PACK. AS THE UPPER TROF CROSSES THE UPPER MID-ATLANTIC BY 05/1800Z...THE 12Z CMC/ECMWF/ECMWF ENSEMBLE MEAN DO END UP SLOWER THAN THE QUICKER CONSENSUS. GIVEN THE ECMWF SOLUTION APPEARS TO BE PLAYING CATCH UP WITH OTHER MODELS...STILL DO NOT FEEL COMFORTABLE INCLUDING THE 12Z ECMWF/ECMWF ENSEMBLE MEAN IN THIS PREFERENCE. FEEL LIKE THE MIDDLE GROUND WILL CONTINUE TO BE THE BETTER SPOT TO SETTLE WITH AS THE 00Z GFS MAY BE TOO QUICK AND IS ALSO FASTER THAN ITS 18Z GEFS MEAN. THE PREFERENCE HERE IS A BLEND OF THE 00Z NAM WITH THE 12Z UKMET. SUCH A 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... PRELIMINARY PREFERENCE: BLEND OF THE 18Z GEFS/12Z ECMWF ENSEMBLE MEANS FORECAST CONFIDENCE: 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 12Z CMC/UKMET BOTH SHOW A SOUTHWARD PUSH WHICH IS NOT SEEN IN ANY OF THE OTHER DETERMINISTIC/ENSEMBLE GUIDANCE. THE ENSEMBLE MEANS VARY IN THEIR SOLUTIONS AS WELL WITH THE 12Z ECMWF ENSEMBLE MEAN BEING SOUTH OF THE 18Z GEFS MEAN WHILE THE 21Z SREF MEAN SITS WELL TO THE NORTH. WILL RELY ON ENSEMBLE MEANS HERE AND RECOMMEND A COMBINATION OF THE 18Z GEFS/12Z ECMWF ENSEMBLE MEANS WITH THE BELIEF THE 21Z SREF MEAN IS TOO SUPPRESSED. ...SERIES OF SHORTWAVES AFFECTING THE PACIFIC NORTHWEST... PRELIMINARY PREFERENCE: THROUGH 06/1200Z: BLEND OF THE 00Z NAM/12Z ECMWF...THEREAFTER...A BLEND OF THE 18Z 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 12Z 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/12Z ECMWF THROUGH 06/1200Z. THERE IS MUCH MORE SPREAD LATE IN THE PERIOD WITH THE TIMING OF A AMPLIFIED WAVE APPROACHING THE CA/OR BORDER LATE FRIDAY/EARLY SATURDAY. ON THE SLOWER SIDE OF THE EQUATION ARE THE 00Z NAM/GFS AND 12Z UKMET WHILE THE 12Z ECMWF REPRESENTS THE FASTEST SOLUTION. FEEL A BLEND OF THE ENSEMBLE MEANS WILL SUFFICE. REGARDLESS OF THE PREFERENCE...THE HEAVY RAINFALL SIGNAL CONTINUES INTO DAY 3 WITH A STRONG SIGNAL OVER THE SHASTA RANGE. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... RUBIN-OSTER