MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1232 PM EST SAT FEB 25 2017 VALID FEB 25/1200 UTC THRU MAR 01/0000 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 12Z NAM/GFS EVALUATION INCLUDING PRELIMINARY PREFERENCES ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ NEGATIVELY TILTED MID-LEVEL SHORTWAVE ACROSS THE NORTHEAST TONIGHT ALONG WITH ATTENDANT COLD FRONT ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GENERAL MODEL BLEND CONFIDENCE: ABOVE AVERAGE THE MODELS SHOW SIMILARLY WITH THIS SYSTEM. FAST MOVING MID-LEVEL SHORTWAVE TRACKING FROM THE NRN PLAINS THIS EVENING TO THE GREAT LAKES SUN EVENING ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GENERAL MODEL BLEND CONFIDENCE: SLIGHTLY ABOVE AVERAGE CONTINUED CONVERGENCE OF MODEL SOLUTIONS REGARDING THE DEPTH AND TIMING OF A SHORTWAVE PASSING OVER THE GREAT LAKES REGION SUN EVENING INCREASES CONFIDENCE IN A GENERAL MODEL COMPROMISE. MODELS THAT WERE IN THE MIDDLE OF THE SPREAD IN PREVIOUS CYCLES HAVE EXHIBITED GOOD RUN TO RUN CONTINUITY. SHORTWAVE SLIDING SOUTH OFF OF CALIFORNIA TODAY AND REACHING THE SRN PLAINS LATE SUN...SHEARING INTO CONFLUENT FLOW ACROSS THE CENTRAL U.S. MON INTO TUES ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GENERAL MODEL BLEND CONFIDENCE: AVERAGE THE MODELS SHOW ONLY MINOR DIFFERENCES THROUGH SUN NIGHT AS THE WEAKENING WAVE REACHES THE SRN PLAINS. ALL OF THE MODELS SHOW REASONABLY GOOD AGREEMENT THROUGHOUT BUT THERE ARE SOME SMALL DIFFERENCES WORTH NOTING. THE 00Z CMC SHOWS GREATER INTERACTION WITH THE AFOREMENTIONED SHORTWAVE AND A MORE ELONGATED FEATURE TO ITS NORTH BY 00Z/27 WHEREAS THE 12Z NAM/GFS SHOW MORE SEPARATION. THE END RESULT IS A MORE TRACKABLE WAVE IN THE 00Z CMC PAST 12Z/27 AND LESS SO IN THE 12Z GFS/NAM WITH THE 12Z GFS A BIT FASTER THAN THE MODEL CONSENSUS. GIVEN THE EXPECTED WEAK NATURE OF THE FEATURE AS IT CROSSES EAST OF THE MISSISSIPPI...THE DIFFERENCES DESCRIBED ABOVE ARE CONSIDERED MINOR ENOUGH THAT A GENERAL MODEL BLEND CAN BE UTILIZED FOR THIS SYSTEM. NEXT SHORTWAVE DROPPING OUT OF COASTAL BC TO THE NWRN U.S. COAST SUNDAY INTO MON WITH ADDITIONAL ENERGY FROM THE NW PHASING WITH OFFSHORE UPPER LOW THAT WILL SWING THROUGH SOUTHERN CA BY TUES ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 12Z GFS/00Z ECMWF BLEND CONFIDENCE: AVERAGE THE GFS SLOWED THE PROGRESSION OF THE SHORTWAVE PASSING ACROSS THE NORTHWEST U.S. SUN NIGHT COMPARED TO PREVIOUS RUNS TO NOW BE IN GOOD AGREEMENT WITH THE REMAINING DETERMINISTIC MODELS. ALL OF THE MODELS TRENDED EAST WITH THE REMNANT CLOSED LOW CURRENTLY NORTHEAST OF HAWAII WITH ALL OF THE LATEST DETERMINISTIC GUIDANCE IN GOOD AGREEMENT THROUGH 12Z/28 REGARDING THE BASE OF THE LONGWAVE TROUGH OVER THE WEST COAST TUE MORNING. ONLY A FEW ENSEMBLE MEMBERS FROM THE ECMWF/GEFS/CMC SHOW THE HAWAII LOW LAGGING BEHIND THE CONSENSUS. AT THE SURFACE...A LOW IS FORECAST TO TRACK ACROSS THE PLAINS EARLY ON TUE AHEAD OF THE LEADING EDGE OF THE TROUGH AXIS SHIFTING EAST AND SOME MINOR PLACEMENT DIFFERENCES WITH A SHORTWAVE ON THE LEE SIDE OF THE MID-UPPER LEVEL TROUGH. ENSEMBLES SCATTER LOW PLOTS SHOW THE GREATEST POTENTIAL FOR A SURFACE LOW 12Z/28 TO BE FROM N-CNTRL TO NERN KS BUT SPREAD GOES AS FAR NORTH AS SOUTH DAKOTA AND ONE OR TWO ECMWF MEMBERS IN NRN OKLAHOMA. THIS POSITION IS NEAREST TO THE 12Z GFS...00Z ECMWF...BUT PERHAPS A TAD NORTH OF THE GFS/ECMWF COMBO THROUGH 00Z/1. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... OTTO