MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1122 AM EST THU MAR 06 2014 VALID MAR 06/1200 UTC THRU MAR 10/0000 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 12Z NAM/GFS EVALUATION WITH PRELIMINARY MODEL PREFERENCES ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ NAM/GFS INITIALIZATION ERRORS DO NOT SEEM TO DEGRADE THEIR SHORT RANGE FORECASTS. DISTURBANCE MOVING BY THE PACIFIC NW LATE SATURDAY ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: NON-NAM COMPROMISE CONFIDENCE: AVERAGE THE NON-NAM GUIDANCE IS AGREEABLE CONCERNING THE SMALL CYCLONE EXPECTED TO BYPASS QUILLAYUTE WA LATE SATURDAY, NAVIGATING AROUND A LARGER PACIFIC CYCLONE OFFSHORE THE ALASKAN PANHANDLE. USING THE MODEL CONSENSUS AS A GUIDE, A NON-NAM COMPROMISE IS PREFERRED WITH AVERAGE CONFIDENCE. NRN STREAM SHORTWAVE BYPASSING NEW ENGLAND SUN AM ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: UKMET/ECMWF COMPROMISE CONFIDENCE: AVERAGE MODEL SPREAD IS INCREASING WITH THIS SYSTEM, WHICH THE 12Z GFS/12Z NAM PROGRESS SLOWER THAN THE OTHER GUIDANCE PAST THE GREAT LAKES AND NEW ENGLAND. THE SYSTEM IS MOVING THROUGH THE BASE OF A VERY BROAD CANADIAN TROUGH, WHICH ARGUES FOR QUICKER PROGRESSION RATHER THAN ANY SOLUTION SLOWER OR MORE AMPLIFIED. THE 06Z GEFS/00Z ECMWF ENSEMBLE MEANS AGREE WITH THIS SYNOPTIC PREMISE. PREFER A COMPROMISE OF THE UKMET/ECMWF SOLUTIONS WITH AVERAGE CONFIDENCE CONSIDERING ITS PROGRESSIVE NATURE AND EXISTING MODEL SPREAD. SOUTHERN STREAM TROUGH MOVING INTO NRN MEX SUN ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: ECMWF/UKMET/CANADIAN COMPROMISE CONFIDENCE: ABOVE AVERAGE THE 12Z NAM IS LESS AMPLIFIED WITH THIS TROUGH, KEEPING A BULK OF THE ENERGY WITHIN IT IN TEXAS RATHER THAN LETTING IT DIG INTO MEXICO. THE UPSTREAM RIDGE REACHES ITS PEAK AMPLIFICATION SATURDAY, WHICH SHOULD ALLOW THE SYSTEM TO DIG FARTHER SOUTH AND SOUTHWESTWARD. THIS PATTERN RESEMBLES WHAT IS KNOWN AS AN ANTICYCLONE WAVE BREAKING EVENT, WHICH FAVORS THE NON-NAM GUIDANCE MOST. THE 12Z GFS, HOWEVER, MOVES THE NORTHERN PORTION OF THIS SYSTEM ACROSS THE LOWER MISSISSIPPI VALLEY QUICKER THAN THE OTHER GUIDANCE, WHICH APPEARS DUE TO ITS SLOWER-MOVING NORTHERN STREAM TROUGH NEAR THE GREAT LAKES/NEW ENGLAND. SINCE THIS IS A KNOWN GFS BIAS ANYWAY, BELIEVE A NON-GFS SOLUTION WOULD BE MOST PRUDENT. THE PREFERENCE IS FOR A COMPROMISE OF THE 00Z ECMWF/00Z UKMET/00Z CANADIAN WITH ABOVE AVERAGE CONFIDENCE CONSIDERING THE SYNOPTIC PATTERN IN WHICH IT IS EMBEDDED. NRN STREAM SHORTWAVE BYPASSING NEW ENGLAND SAT AM ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GENERAL MODEL COMPROMISE CONFIDENCE: HIGH THE GUIDANCE SHOWS GOOD AGREEMENT WITH THIS SYSTEM. TO DEAL WITH ANY LINGERING DETAIL ISSUES, PREFER A GENERAL MODEL COMPROMISE WITH HIGH CONFIDENCE. DEEP CYCLONE MOVING OUT OF THE SOUTHEAST FRI NIGHT ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: NON-NAM COMPROMISE CONFIDENCE: AVERAGE THE 12Z NAM CONTINUES TO BE THE SLOWEST PIECE OF GUIDANCE WITH THIS SYSTEM'S PROGRESSION, WHILE THE 12Z GFS IS ONE OF THE QUICKER SOLUTIONS. WHILE THE 12Z GFS SHOWS SIGNS OF CONVECTIVE/GRIDSCALE FEEDBACK. THE SURFACE LOW DOES HAVE ASSOCIATED CONVECTION IN ITS VICINITY, SO IT MAY NOT BE THAT FAR OFF BASE. AS THE NAM IS TRENDING QUICKER, AND THAT THE SYSTEM SHOULD BE PICKING UP THE PACE OF ITS PROGRESSION SOUTH OF THE APPROACHING QUASI-ZONAL NORTHERN STREAM, BELIEVE THE NAM IS TOO SLOW. THE PREFERENCE IS FOR A NON-NAM COMPROMISE WITH AVERAGE CONFIDENCE CONSIDERING THE LINGERING DETAIL ISSUES SEEN IN THE GUIDANCE. SEE WPC WINTER WEATHER AND QPF DISCUSSIONS FOR THOUGHTS ON PRECIPITATION TYPE AND AMOUNTS EXPECTED WITH THIS SYSTEM. www.wpc.ncep.noaa.gov/html/model2.shtml... ROTH