MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1135 PM EST MON FEB 10 2014 VALID FEB 11/0000 UTC THRU FEB 14/1200 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 00Z NAM/GFS EVALUATION WITH PRELIMINARY PREFERENCES ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ NAM/GFS INITIALIZATION ERRORS DO NOT APPEAR TO SIGNIFICANTLY AFFECT THEIR LARGE SCALE OUTPUT. EASTERN U.S. CYCLONE AND WINTER STORM ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: BLEND OF 12Z UKMET / 12Z EC MEAN CONFIDENCE: AVERAGE THE 00Z NAM IS DIFFERENT EARLY IN THE SHORT RANGE...REGARDING A NRN STREAM SHORTWAVE CURRENTLY ENTERING BRITISH COLUMBIA EARLY THIS MORNING. THIS CONTINUES DOWNSTREAM WITH A SLOWER/NORTHWARD DISPLACED MID-LEVEL JET STREAK BY WED MORNING OVER THE CNTRL HIGH PLAINS...A FEATURE WHICH HOLDS GOOD CONTINUITY IN THE GFS/ECMWF/UKMET. THIS RESULTS IN A LESS AMPLIFIED UPPER TROUGH IN THE NAM BY EARLY THU OVER THE CNTRL APPALACHIANS. THE ENSEMBLE SCATTER LOW PLOTS ARE MORE TIGHTLY CLUSTERED THAN YESTERDAY...WHICH SHOULD BE EXPECTED...BUT HAVE MADE A WHOLESALE SHIFT SLOWER AND WEST. THE ECMWF MEMBERS ARE ON THE WEST SIDE OF THE LOW PLOT ENVELOPE...FOLLOWED BY THE GEFS/CMC MEMBERS JUST RIGHT OF THE ECMWF MEMBER CLUSTER DURING THE DAY ON THURSDAY. THIS PRECLUDES USE OF THE 12Z CMC WHICH IS MUCH FASTER THAN THE CONSENSUS. DUE TO THE ECMWF AND ITS MEAN BEING ON THE WESTERN SIDE OF THE AVAILABLE GUIDANCE WITH THE SURFACE LOW WHICH TRACKS UP THE EAST COAST... DESPITE THE WESTWARD TREND SEEN IN ALL OF THE MODELS...THE SAFER PLACE IS JUST A BIT EAST OF THE ECMWF. THE 00Z GFS POSITION LOOKS REASONABLE...BUT APPEARS TOO WEAK AND MAY HAVE SOME CONVECTIVE FEEDBACK WHICH DEVELOPS EARLY THURSDAY MORNING. THE 12Z UKMET APPEARS TO BE A DECENT COMPROMISE WHEN BLENDED WITH THE 12Z EC MEAN...WITH THE EC MEAN A BIT EAST OF THE OPERATIONAL ECMWF. COLD FRONT MOVING THROUGH THE DAKOTAS TUE NIGHT AND ENTERING THE GREAT LAKES WED ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 00Z GFS / 12Z ECMWF / 12Z CMC COMPROMISE CONFIDENCE: ABOVE AVERAGE THERE HAS BEEN CONVERGENCE IN THE MODELS SINCE YESTERDAY WITH THE TIMING OF THIS FRONT AND THE ASSOCIATED LOBE OF VORTICITY SWINGING SOUTH INTO SRN CANADA. THE UKMET HAS SLOWED DOWN THE FRONTAL TIMING A BIT TO BE MORE IN LINE WITH THE REMAINING MODEL CONSENSUS BUT IS STILL ON THE FAST SIDE. THE 00Z NAM IS THE SLOWEST DETERMINISTIC MODEL...BUT NOT BY MUCH. THE NAM IS SLOWER DUE TO REASONS REFERENCED ABOVE IN THE EASTERN U.S. CYCLONE HEADER. MEANWHILE...THE 00Z GFS...12Z ECMWF...12Z CMC MAKE UP A GOOD COMPROMISE IN LINE WITH THE LATEST ENSEMBLE MEANS. SHORTWAVE INTO THE NORTHWEST LATE TUESDAY SURFACE LOW FORMING IN EASTERN MONTANA LATE WEDNESDAY ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: BLEND OF 12Z ECMWF/UKMET/CANADIAN CONFIDENCE: AVERAGE THE MODELS SHOW BEGIN TO DIVERGE LATE WEDNESDAY AS THE CORRESPONDING MID-LEVEL SHORTWAVE CUTS THROUGH A LOW AMPLITUDE RIDGE AXIS OVER THE NORTHWEST U.S. / WRN CANADA. THE 00Z NAM/GFS HAVE TRENDED WEAKER WITH THIS SHORTWAVE AND WEAKER WITH THE SURFACE LOW AND THE NAM ENDS UP ON THE NRN SIDE OF THE MODEL SPREAD BY 12Z/13...THU MORNING.. ENSEMBLE SCATTER LOW PLOTS INDICATE TIGHT CLUSTERING IN THE ECMWF/CMC MEMBERS SOUTH OF THE NAM...BUT THE GEFS LOWS ELONGATE WNW TO ESE VALID 12Z/13 OVER THE N=CNTRL CONUS. THE ECMWF/UKMET/CMC HAVE HELD GOOD AGREEMENT WITH THEIR PREVIOUS RUNS AND GIVEN DECENT AGREEMENT IN THE ENSEMBLE MEANS...THE 12Z ECMWF/UKMET/CMC WILL CONTINUE TO BE PREFERRED. SHORTWAVE APPROACHING THE PACIFIC NORTHWEST LATE THURSDAY ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: BLEND OF THE 12Z OPERATIONAL MODELS CONFIDENCE: AVERAGE THE OPERATIONAL MODELS SHOW REMARKABLE AGREEMENT HERE...FOR AN AREA OF THE PACIFIC WHICH HAS SEEN MUCH TURMOIL RECENTLY. BY 12Z/14...FRI MORNING...THE 12Z UKMET IS A BIT SLOW AND THE 12Z CMC IS A BIT FAST COMPARED TO THE REMAINING MODELS BUT THEY HAVE BEEN TRENDING TOWARD THE MIDDLE...BEST REPRESENTED BY THE 00Z NAM/GFS/ECMWF. CONFIDENCE IS ONLY AVERAGE DUE TO THE TIME SCALE OF THIS SYSTEMS IMPACT ON THE WEST COAST...ACCOUNTING FOR POTENTIAL MODEL ADJUSTMENTS. www.wpc.ncep.noaa.gov/html/model2.shtml... OTTO