MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 149 AM EST TUE MAR 03 2015 VALID MAR 03/0000 UTC THRU MAR 06/1200 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 00Z MODEL EVALUATION WITH FINAL PREFERENCES ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ NAM/GFS INITIALIZATION ERRORS DO NOT SEEM TO DEGRADE THEIR SHORT RANGE FORECASTS. SHORTWAVE CROSSING THE ROCKIES THIS MORNING AND ASSOCIATED SFC LOW + COLD FRONT MOVING OUT INTO THE CNTRL PLAINS THROUGH TODAY UPPER TROUGH AXIS DROPPING OUT OF CANADA INTO THE N-CNTRL U.S. TUE EVENTUAL STRONG COLD FRONT REACHING THE SOUTHEAST THU MORNING ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 00Z GFS / 00Z ECMWF BLEND CONFIDENCE: A LITTLE BELOW AVERAGE BY TUE EVENING...TIMING DIFFERENCES BEGIN TO APPEAR WITH A LEAD COLD FRONT EXTENDING FROM THE OHIO VALLEY BACK INTO THE SRN PLAINS. THE 00Z UKMET REMAINS SLOWEST WITH THIS BOUNDARY AND THE 00Z GFS BEGINS TO PULL AHEAD OF THE REMAINING DETERMINISTIC GUIDANCE. THROUGH 12Z/04...ENSEMBLE SPAGHETTI HEIGHTS AT 500 MB HAVE SHIFTED NORTH COMPARED TO SUN EVENING FOR LOCATIONS FROM THE CNTRL PLAINS TO LAKES ERIE AND ONTARIO...IN THE DIRECTION OF THE SLOWER UKMET...BUT THE UKMET REMAINS ON THE EDGE OF THE ENSEMBLE SPREAD. BEYOND 12Z/04...THE 00Z NAM SHOWS UP AS A LOW PROBABILITY OUTLIER WITH RESPECT TO ENSEMBLE SPAGHETTI HEIGHTS...AND THE LATEST DETERMINISTIC MODEL CONSENSUS. THE 00Z GFS IS TOWARD THE FASTER SIDE OF THE GUIDANCE...AND GIVEN TRENDS IN THE DIRECTION OF THE SLOWER GUIDANCE...PREFER TO STAY A BIT SLOWER THAN THE FASTER GFS. THE SLOWER 12Z UKMET ADJUSTED FASTER WITH ITS 00Z RUN AND THE FASTER 12Z ECMWF ADJUSTED SLOWER. CONVERGENCE! THEREFORE...SINCE THE 00Z NAM IS NOT BEING CONSIDERED AND GIVEN THE TRENDING OF MODEL SOLUTIONS...AND CONSIDERATION OF THE LATEST ENSEMBLE MEANS...A 00Z GFS/ECMWF BLEND IS PREFERRED...WHICH IS A BIT FASTER THAN THE LATEST 00Z UKMET. CLOSED LOW CURRENTLY OFF SRN CALIFORNIA CROSSING BACK INTO THE SOUTHWEST LATE TUESDAY REMNANT LOWER MID-LEVEL HEIGHTS OVER THE SWRN U.S. BORDER THROUGH THE END OF THE WEEK ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 00Z GFS / 00Z ECMWF BLEND CONFIDENCE: A LITTLE BELOW AVERAGE THE MODELS SHOW REASONABLY CLOSE AGREEMENT HERE AFTER TRENDING TOWARD A COMMON MIDDLE GROUND...BUT WITH THE REMAINING SPREAD...PREFER TO STAY TOWARD THE MIDDLE. THIS IS BEST REPRESENTED BY THE 00Z GFS AND 00Z ECMWF...BOTH MODELS SHOWING ONLY MINOR RUN TO RUN CHANGES SINCE THEIR 00Z RUNS YESTERDAY. POTENTIAL SHORTWAVE OVER SWRN CANADA FRI MORNING ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 00Z GFS/ECMWF/CMC BLEND CONFIDENCE: AVERAGE THE MODELS ARE FORECASTING SHORTWAVE ENERGY FROM THE GULF OF ALASKA TO TRACK INTO WRN CANADA ON THU...ATOP A STRONG MID-LEVEL RIDGE CENTERED NEAR THE COAST OF CNTRL CALIFORNIA. THE 12Z ECMWF ENSEMBLE MEAN IS LESS AMPLIFIED THAN THE 12Z ECMWF WITH ENSEMBLE SPAGHETTI HEIGHTS SHOWING A FAIR AMOUNT OF SPREAD BY 12Z/06...BUT THE 00Z ECMWF HAS ADJUSTED FLATTER. GIVEN THE STRONG RIDGE IN PLACE ACROSS THE WEST COAST OF NORTH AMERICA...PREFER TO STAY LESS AMPLIFIED...AND THE 00Z ECWFM/UKMET/CMC SUPPORT THIS IDEA WITH A TIMING SLOWER THAN THE NAM. THEREFORE THE PEFERENCE IS BEING ADJUSTED SLIGHTLY TO REPLACE THE NAM WITH THE ECMWF AND CMC WHICH SHOW SIMILAR AMPLITUDE BUT A SLOWER TIMING THAN THE 00Z GFS/NAM. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... OTTO