MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1242 PM EDT THU MAR 27 2014 VALID MAR 27/1200 UTC THRU MAR 31/0000 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 12Z NAM/GFS EVALUATION WITH PRELIMINARY PREFERENCES ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ NAM/GFS INITIALIZATION ERRORS DO NOT SEEM TO DEGRADE THEIR SHORT RANGE FORECASTS. CLOSED LOW SETTING UP OFF OF THE PACIFIC NORTHWEST SUN NIGHT ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 12Z GFS...00Z UKMET COMPROMISE CONFIDENCE: AVERAGE THE LATEST ENSEMBLE MEANS SUPPORT A CLOSED LOW POSITION/STRENGTH THAT IS CLOSEST TO A BLEND OF THE 12Z GFS AND 00Z UKMET. THE NAM IS A BIT SLOWER...AND THE 00Z ECMWF IS FASTER AND DISPLACED SOUTH AND EAST OF THE MEANS BY 00Z/31. THE 00Z CMC IS FASTER AND DISPLACED EAST OF THE MEANS BY 00Z/31 WITH THE GFS/UKMET REPRESENTING THE MIDDLE GROUND. ALL OF THE MODELS HAVE SHOWN SOME QUICKENING TRENDS SINCE YESTERDAY...BUT THE GFS IS THE MOST CONSISTENT FROM THE 00Z/27 AND 12Z/26 MODEL CYCLES. MID-LEVEL TROUGH AXIS REACHING THE WEST COAST LATE SAT ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GENERAL MODEL COMPROMISE CONFIDENCE: AVERAGE THERE IS LIMITED MODEL SPREAD REMAINING WITH THE LATEST GUIDANCE TRENDING TOWARD EACH OTHER. THEREFORE A GENERAL MODEL COMPROMISE CAN BE USED. SHORTWAVE AMPLIFYING INTO THE EAST COAST STATES FOR THE WEEKEND ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 12Z GFS...00Z ECMWF COMPROMISE CONFIDENCE: AVERAGE THE 12Z NAM IS UNIQUE WITH RESPECT TO THE REMAINING GUIDANCE IN HAVING A LESS AMPLIFIED SHORTWAVE PROGRESSING TOWARD THE APPALACHIANS ON SAT. ENSEMBLES AND TRENDS WOULD SUPPORT A STRONGER/SLOWER SHORTWAVE THAN SEEN IN THE 12Z NAM. DIFFERENCES IN MID-LEVEL HEIGHTS UPSTREAM ACROSS THE WEST APPEAR TO BE SHRINKING...WITH A CONSENSUS FOR TROUGHING...WHICH IS RESULTING IN GREATER RIDGE AMPLIFICATION ACROSS THE GREAT LAKES ON SUN COMPARED TO YESTERDAY. THIS IS RESULTING IN A STRONGER TROUGH ALONG THE EAST COAST STATES BY SUN MORNING...WITH THE 12Z GFS...00Z ECMWF REPRESENTING SIMILAR SOLUTIONS AND A CLOSE COMPROMISE WITHIN THE MIDDLE OF THE LATEST ENSEMBLE SPREAD. THE ECMWF APPEARS TO BE ON THE DEEPER SIDE OF THE ENSEMBLE SPREAD BUT BLENDING WITH THE GFS AND GIVEN THE AFOREMENTIONED SYNOPTIC SETUP APPEARS REASONABLE. THE 00Z UKMET IS CLOSE TO THIS BLEND BUT ITS SURFACE LOW APPEARS TOO FAR INLAND BY 12Z/SUN GIVEN THE LOCATIONS OF THE ENSEMBLE SCATTER LOT PLOTS. GREAT LAKES SHORTWAVE AND SFC LOW TONIGHT/FRI ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 12Z GFS / 00Z ECMWF BLEND CONFIDENCE: ABOVE AVERAGE MINOR DIFFERENCES WITH TIMING/PLACEMENT OF THIS SYSTEM...WITH THE 12Z NAM FASTEST/WEAKEST AND THE 00Z CMC SLOWEST/STRONGEST BY 12Z/FRI ACROSS THE GREAT LAKES. THE 00Z UKMET IS SLIGHTLY SLOWER/STRONGER THAN THE CONSENSUS...BUT A BLEND OF THE 12Z GFS AND 00Z ECMWF REPRESENT A POSITION/STRENGTH THAT IS CLOSE TO THE MIDDLE OF THE DETERMINISTIC/ENSEMBLE SPREAD. www.wpc.ncep.noaa.gov/html/model2.shtml... OTTO