MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 137 AM EDT FRI MAR 14 2014 VALID MAR 14/0000 UTC THRU MAR 17/1200 UTC ...CORRECTION FOR MODEL PREFERENCE IN FIRST SYSTEM ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... OOZ NAM/GFS EVALUATION WITH PRELIMINARY PREFERENCES ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ NAM/GFS INITIALIZATION ERRORS DO NOT SEEM TO DEGRADE THEIR SHORT RANGE FORECASTS. DEEP CYCLONE MOVING INTO BRITISH COLUMBIA SAT & SUN INCREASING ONSHORE FLOW IN THE PACIFIC NW SUN & MON ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GENERAL MODEL COMPROMISE THROUGH 00Z MON NON 00Z NAM COMPROMISE AFTER 00Z MON CONFIDENCE: AVERAGE THE GUIDANCE IS IN REASONABLE AGREEMENT WITH THIS FEATURE THROUGH 00Z MON...SO THE PREFERENCE IS FOR A GENERAL MODEL COMPROMISE UNTIL THAT POINT IN TIME. AFTER ABOUT 00Z MON...THE NAM IS ALONE IN NOT SEPARATING AN APPRAOCHING UPPER TROUGH TOWARD THE WEST COAST...WHEREAS THE REMAINING DETERMINISTIC/ENSEMBLE MODEL GUIDANCE HOLDS A CLOSED LOW BACK NEAR THE VICINITY OF 30 N / 150 W. SHORTWAVE WEAKENING EWD FROM ITS CURRENT POSITION OVER THE SOUTHWEST ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: NON 00Z NAM COMPROMISE THROUGH 00Z/16 NON 00Z NAM/GFS COMPROMISE AFTER 00Z/16 CONFIDENCE: ABOVE AVERAGE THE NAM IS SIGNIFICANTLY SLOWER WITH THIS FEATURE BY THE TIME IT REACHES WEST TEXAS ON SAT COMPARED TO A STRONG CONSENSUS OF THE REMAINING MODEL GUIDANCE. THE SLOWER NAM SHORTWAVE THEN MERGES AN AMPLIFYING WAVE FROM THE NORTH RESULTING IN A POWERFUL STORM SYSTEM OVER THE LOWER MISSISSIPPI BY SUN NIGHT. THE 00Z GFS APPEARS TO DEVELOP SOME CONVECTIVE FEEDBACK AROUND 06Z/16 OVER ARKANSAS WHICH MAY CONTAMINATE ITS SOLUTION GOING FORWARD OVER THE DEEP SOUTH AND MID-ATLANTIC. THIS LEAVES THE AGREEABLE REMAINING MODEL CONSENSUS. SHORTWAVE AMPLIFYING INTO THE SRN PLAINS FOR SUN SURFACE CYCLONE DEVELOPING OVER THE LOWER MISSISSIPPI VALLEY ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 12Z ECMWF/12Z CMC BLEND CONFIDENCE: AVERAGE SINCE THU EVENING...DETERMINISTIC AND ENSEMBLE MODEL GUIDANCE HAS TRENDED AWAY FROM MORE SEPARATION IN A POSITIVELY TILTED UPPER TROUGH EXTENDING FROM THE MID-MISSISSIPPI VALLEY INTO NERN MEXICO BY MID-DAY SUN...RESULTING IN A SOMEWHAT FASTER UPPER TROUGH PROGRESSION ACROSS THE GULF COAST. THERE IS FAIRLY GOOD AGREEMENT THROUGH SUNDAY MORNING OUTSIDE OF THE OVERDEVELOPED NAM (SEE SECTION ABOVE). MOVING BEYOND SUNDAY EVENING...THERE IS DECENT AGREEMENT IN THE 21Z SREF/18Z GEFS/12 ECMWF MEANS AT 500 MB BUT GREATER SPREAD IN THE DETERMINISTIC SOLUTIONS. BY SUN NIGHT...THE 00Z GFS DEPICTS A STRONG CLOSED LOW CENTERED OVER NRN TEXAS WHILE THE 12Z CMC HINTS AT A SMALLER CLOSED LOW OVER SERN TX. ENSEMBLE SPAGHETTI HEIGHTS DO NOT SUPPORT THE 00Z GFS...AND SUGGEST THE 12Z ECMWF COULD BE A LITTLE SLOW. GIVEN THE SURFACE LOW TRACKING THROUGH TN IN THE 12Z UKMET IS ALMOST OUTSIDE OF THE ENSEMBLE SPREAD...PREFER A BLEND OF THE FASTER AND SLOWER SOLUTIONS...HERE THE 12Z ECMWF/CMC. SURFACE LOW BYPASSING THE GREAT LAKES/NEW ENGLAND FRI & SAT ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GENERAL MODEL COMPROMISE CONFIDENCE: AVERAGE THE GUIDANCE IS IN REASONABLE AGREEMENT WITH THIS FEATURE...SUCH THAT A GENERAL MODEL COMPROMISE IS PREFERRED TO DEAL WITH ANY LINGERING DETAIL ISSUES. www.wpc.ncep.noaa.gov/html/model2.shtml... OTTO