MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 138 AM EST WED FEB 25 2015 VALID FEB 25/0000 UTC THRU FEB 28/1200 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 00Z MODEL EVALUATION...INCLUDING FINAL PREFERENCES ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ SHORTWAVE TROUGH CROSSING THE GREAT LAKES/NORTHEAST TODAY SURFACE LOW IMPACTING EASTERN NEW ENGLAND TODAY ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: NON 00Z NAM BLEND CONFIDENCE: SLIGHTLY ABOVE AVERAGE MINOR WEST-EAST SPREAD REMAINS WITH THE TRACK OF A SURFACE LOW FORECAST TO RAPIDLY DEEPEN AS IT TRACKS INTO NOVA SCOTIA LATER TODAY. THE 00Z NAM IS ON THE DEEPER/EASTERN SIDE WITH THE LOW TRACK...THE 00Z GFS IS ALSO EAST...WHILE THE 00Z ECMWF/UKMET ARE ON THE WESTERN SIDE. THE LATEST ENSEMBLE MEANS SUPPORT THE MIDDLE GROUND 00Z CMC...BUT GIVEN AN EWD SHIFT IN THE PREVIOUSLY STEADY GFS WHOSE 00Z RUN AGREES WITH THE 00Z NAM...AND THE FACT THAT THE VALID TIME IS WITHIN 24 HOURS...WILL GIVE SOME CREDIT TO THE GFS POSITION. A GENERAL MODEL COMPROMISE CAN BE USED...OUTSIDE OF THE STRONGER/EASTERN NAM. SHORTWAVE TROUGH TRACKING FROM TEXAS TO THE GULF COAST STATES TODAY SURFACE LOW TRACKING JUST OFF OF THE SOUTHEAST COAST ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 00Z GFS/ECMWF/UKMET BLEND CONFIDENCE: AVERAGE MINOR BUT SIGNIFICANT DIFFERENCES REMAIN WITH THIS SYSTEM. MODEL ANALYSES FROM THE NAM/GFS/ECMWF/UKMET/CMC ARE WITHIN REASON BUT THE NORTH/SOUTH PLACEMENT OF LOW-MID LEVEL FEATURES DIFFERS SOME AMONG THE LATEST MODELS THROUGH THE NEXT 24-36 HOURS. THE NAM IS ON THE STRONGER SIDE OF THE GUIDACE WITH THE 850-700 MB LOW CROSSING THE LOWER MISS VALLEY. THE 00Z ECMWF ADJUSTED NORTH A BIT FROM ITS PREVIOUIS RUN AND THE 00Z UKMET STILL APPEARS USABLE HERE. WHILE THE 00Z GFS/ECMWF/UKMET ARE NOT IDENTICAL...THESE MODELS SPLIT THE DIFFERENCE IN LATITUDE BUT SHOW SIMILARLY IN STRENGTH REGARDING THIS SYSTEM. THIS IS ALSO TRUE FOR THE SURFACE LOW WHICH STRENGTHENS AS IT PASSES JUST OFF OF THE SOUTHEAST COAST WED NIGHT/THU MORNING. STRENGTHENING TROUGHING OVER THE GREAT LAKES/NORTHEAST THROUGH FRI SURFACE LOW TRACKING INTO MISSOURI TONIGHT AND WEAKENING ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GENERAL MODEL COMPROMSIE CONFIDENCE: ABOVE AVERAGE THE MODELS SHOW SIMILARLY WITH THIS SYSTEM. UPPER TROUGH AMPLIFYING OVER THE WEST FRI INTO SAT ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: BLEND OF THE 00Z GFS/ECMWF/CMC...CLOSE TO 12Z EC MEAN CONFIDENCE: BELOW AVERAGE ENSEMBLE SPREAD REMAINS LARGE WITH AN UPPER TROUGH FORECAST TO AMPLIFY ACROSS THE WEST LATER THIS WEEK...BUT THE INDIVIDUAL ENSEMBLE MEMBERS HAVE TRENDED AWAY FROM THE STRONGER UKMET SINCE YESTERDAY. CURRENTLY...THE 12Z EC MEAN IS IN THE MIDDLE OF THE LATEST SPREAD AND IS SUPPORTED BY THE 00Z GFS...00Z ECMWF AND 00Z CMC. SINCE THESE MODELS ARE IN THE MIDDLE OF THE LATEST DETERMINISTIC SPREAD AND HAVE SUPPORT FROM THE RELATIVELY AGREEABLE ENSEMBLE MEANS...WILL GO IN THEIR DIRECTION AT THIS TIME. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... OTTO