MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 253 AM EDT MON APR 25 2016 VALID APR 25/0000 UTC THRU APR 28/1200 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 00Z MODEL EVALUATION WITH FINAL PREFERENCES ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ GFS/NAM INITIALIZATION ERRORS DO NOT SEEM TO DEGRADE THEIR SHORT RANGE FORECASTS. SYSTEM MOVING THROUGH THE UPPER MIDWEST/GREAT LAKES/NEW ENGLAND THROUGH TUE ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GENERAL MODEL COMPROMISE CONFIDENCE: AVERAGE ONLY MINOR TIMING DIFFERENCES APPEAR WITH THIS SYSTEM...WITH THE 00Z NAM LIKELY TOO SLOW WHILE THE 00Z GFS HAS TRENDED FASTER...MAYBE TOO FAST. THE DIFFERENCES ARE RELATIVELY MINOR HOWEVER...SO A GENERAL MODEL COMPROMISE SHOULD SUFFICE HERE. DEEP CYCLONE EMERGING INTO THE HIGH PLAINS LATE TUESDAY ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 00Z UKMET CONFIDENCE: BELOW AVERAGE SIGNIFICANT MODEL DIFFERENCES APPEAR DUE TO SUBTLE DIFFERENCES IN VORTICITY WRAPPING AROUND A CLOSED LOW MOVING ACROSS THE WEST ON TUE. NONE OF THE DETERMINISTIC MODELS APPEAR TO HAVE A GOOD HANDLE ON THE EVOLUTION AND RUN TO RUN CHANGES CONTINUE TO AFFECT THE SURFACE EVOLUTION. THE ENSEMBLES CONTINUE TO SHOW WIDE SPREAD AND LIKELY CONVECTION ACROSS THE CNTRL/SRN PLAINS ON TUE MAY INFLUENCE THE PATTERN INTO WED. THE 00Z UKMET IS CLOSEST TO THE ENSEMBLE MEANS AT THIS POINT REGARDING LOW POSITIONS/TIMING...BUT GIVEN A LACK OF AGREEMENT IN THE GUIDANCE...CONFIDENCE IS LOW. WHILE THE 00Z ECMWF APPEARS REASONABLE WITH THE TRACK OF THE 500 MB AND SURFACE LOW...IT CONTINUES TO BE FASTER WITH THE COLD FRONT MOVING THROUGH THE ARKLATEX BY WED EVENING...GIVEN ALL OF THE REMAINING DETERMINISTIC/ENSEMBLE GUIDANCE IS SLOWER. DUE TO THE COMPLEX EVOLUTION OF THE UPPER LOW AND WEAKER ENERGY SOUTH OF THE LOW CENTER...CONFIDENCE IS BELOW AVERAGE WITH A WIDE RANGE OF POSSIBLE ENSEMBLE OUTCOMES. UPPER TROUGH MOVING ACROSS THE GULF OF MEXICO TODAY ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GENERAL MODEL COMPROMISE CONFIDENCE: ABOVE AVERAGE THE MODELS DO NOT SHOW ANY LARGE SCALE DIFFERENCES WITH THIS SYSTEM. DEEP CLOSED LOW CENTERED OVER ERN QUEBEC THROUGH MID WEEK ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GENERAL MODEL COMPROMISE CONFIDENCE: ABOVE AVERAGE THE MODELS SHOW SIMILARLY WITH THIS SYSTEM. SYSTEM APPROACHING THE PACIFIC NORTHWEST TUESDAY AFTERNOON ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: NON 00Z ECMWF COMPROMISE CONFIDENCE: ABOVE AVERAGE THE MODELS SHOW SIMILARLY HERE...THOUGH THE 00Z ECMWF HAS A DIFFERENT ORIENTATION WITH THE UPEPR TROUGH ACROSS THE SOUTHWEST BY THU MORNING...WITH THE REMAINING GUIDANCE MORE AMPLIFIED TOWARD THE SOUTH. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... OTTO