MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 103 PM EDT WED MAR 26 2014 VALID MAR 26/1200 UTC THRU MAR 30/0000 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... ...12Z NAM/GFS EVALUATION ALONG WITH PRELIMINARY PREFERENCES... THERE DID NOT APPEAR TO BE ANY INITIALIZATION ERRORS WITH THE NAM/GFS DEEMED SIGNIFICANT ENOUGH TO IMPACT THEIR FORECASTS. DEPARTING STRONG CYCLONE EAST OF NEW ENGLAND TONIGHT ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GENERAL MODEL COMPROMISE CONFIDENCE: SLIGHTLY ABOVE AVERAGE THERE IS FAIRLY GOOD AGREEMENT IN THE SHORT TERM WITH THIS SYSTEM AS A STRONG SURFACE LOW TRACKS NWD...CLIPPING NOVA SCOTIA TONIGHT. A GENERAL MODEL COMPROMISE IS SUFFICIENT THROUGH THU...AT WHICH POINT THE SYSTEM DEPARTS THE FORECAST AREA. WEAKENING SHORTWAVE TRACKING NEWD FROM THE SRN PLAINS TODAY ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: A GENERAL MODEL COMPROMISE CONFIDENCE: ABOVE AVERAGE DIFFERENCES IN THE LATEST GUIDANCE ARE SMALL ENOUGH SUCH THAT A GENERAL MODEL COMPROMISE CAN BE USED. PAIR OF SURFACE LOWS IMPACTING THE NRN/CNTRL PLAINS TODAY/THU CORRESPONDING COLD FRONT ADVANCING THROUGH THE OHIO VALLEY ON FRI ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: AVERAGE OF THE 00Z ECMWF/12Z GFS (STRENGTH AND POSITION) CONFIDENCE: SLIGHTLY BELOW AVERAGE REGARDING THE SURFACE LOW FORECAST TO TRACK ACROSS SOUTH DAKOTA TONIGHT...AND WEAKEN INTO MINNESOTA THU MORNING...THE MODELS HAVE TRENDED TOWARD A COMMON SOLUTION AND A GENERAL MODEL COMPROMISE CAN BE USED. REGARDING THE SECOND...STRONGER LOW EXPECTED TO TRACK NEWD FROM THE CNTRL PLAINS ON THU...THE 12Z GFS IS CLEARLY THE STRONGEST DETERMINISTIC MODEL WITH THIS SYSTEM...NOTED AS EARLY AS 12Z THU. HOWEVER...THE NAM/GFS HAVE BOTH TRENDED STRONGER COMPARED TO YESTERDAY WHILE THE ECMWF/UKMET/CMC HAVE REMAINED REASONABLY CONSISTENT WITH THE STRENGTH OF THIS SYSTEM. THE 00Z ECMWF IS THE WEAKEST DETERMINISTIC MODEL AND ENDS UP ON THE SOUTH SIDE OF THE DETERMINISTIC MODEL SPREAD. ENSEMBLE SCATTER LOW PLOTS SUPPORT A COMPROMISE OF THE GFS/ECMWF POSITION...AND GIVEN THE STRENGTH DIFFERENCES NOTED BETWEEN THE GFS AND ECMWF...A BLEND OF THE TWO APPEARS THE BEST COMPROMISE. THE PROBLEM WITH THE UKMET/CMC...AND NAM FOR THAT MATTER...IS THEIR NORTHWARD DISPLACED POSITION WITH RESPECT TO THE BETTER ENSEMBLE CLUSTERING. COMPACT CLOSED LOW REACHING THE PACIFIC NORTHWEST TONIGHT SHORTWAVE ENERGY REACHING THE OHIO VALLEY BY EARLY SAT WITH CORRESPONDING SURFACE LOW ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 00Z ECMWF CONFIDENCE: SLIGHTLY BELOW AVERAGE BY LATE FRI...THE MODELS BEGIN TO SIGNIFICANTLY DIVERGE AS THE UPPER TROUGH REACHES THE MISSISSIPPI VALLEY. DIFFERENCES ARE MOSTLY IN DEPTH OF THE UPPER TROUGH...AND LESS WITH TIMING. THE NAM IS THE STRONGEST...EVENTUALLY COMPLETELY CLOSING OFF A MID-LEVEL CENTER BY MID-LATE SAT. MEANWHILE...THE 00Z ECMWF APPEARS TO BE A GOOD MIDDLE GROUND WITH BOTH THE GFS/ECMWF QUITE CONSISTENT WITH THIS SYSTEM OVER THEIR PAST 3 RUNS (CONSIDERING 12Z & 00Z ONLY). THE 12Z GFS IS A LITTLE WEAKER ALOFT AND SOUTH/WEAKER WITH THE SURFACE LOW...WHILE THE 00Z UKMET IS A LITTLE STRONGER ALOFT AND NORTH/STRONGER WITH THE SURFACE LOW. PREFER THE 00Z ECMWF WITH THE 12Z GFS AND 00Z UKMET THE NEXT CLOSEST CHOICES. UPPER TROUGH / MID-LEVEL SHORTWAVE REACHING THE WEST COAST LATE SAT ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: BLEND OF THE 12Z GFS / 00Z ECMWF CONFIDENCE: AVERAGE THERE IS GOOD AGREEMENT WITH THE CENTER OF THE CLOSED MID-LEVEL LOW OFF OF THE PACIFIC NORTHWEST COAST ON SAT...BUT LESS AGREEMENT WITH THE BASE OF THIS TROUGH IMPACTING CALIFORNIA. THE GFS AND ECMWF APPEAR TO SHOW A GOOD MIDDLE GROUND WITH RESPECT TO THE VARIOUS LATITUDE AND TIME DIFFERENCES SEEN WITH THIS FEATURE WITH HEAVY QPF IMPACTS INTO CALIFORNIA...AND SHOW REASONABLE CONTINUITY WITH AGREEMENT FROM THE ENSEMBLE DISPLAYS. www.wpc.ncep.noaa.gov/html/model2.shtml... OTTO