MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 144 AM EST MON MAR 02 2015 VALID MAR 02/0000 UTC THRU MAR 05/1200 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. INITIAL UPPER LOW/TROUGH OVER CALIFORNIA REACHING THE CNTRL ROCKIES MON NIGHT ASSOCIATED SFC LOW / COLD FRONT MOVING OUT INTO THE CNTRL PLAINS TUE MORNING AND THROUGH THE DAY ON TUE ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 00Z GFS...00Z ECMWF BLEND CONFIDENCE: AVERAGE TIMING DIFFERENCES BEGIN TO APPEAR WITH THE REMNANT SHORTWAVE AS IT REACHES THE CNTRL PLAINS EARLY TUE ALONG WITH THE ASSOCIATED COLD FRONT EXTENDING WWD ACROSS THE ROCKIES. THE 00Z NAM AND 00Z CMC ARE SLIGHTLY SLOWER WITH THE SHORTWAVE COMPARED TO THE AGREEABLE 00Z GFS AND 00Z ECMWF. CURRENTLY...THE GFS/ECMWF AGREE WELL WITH THE LATEST ENSEMBLE MEANS DESPITE NOTABLE REMAINING ENSEMBLE SPREAD...WITH THE 00Z UKMET GETTING A BIT AHEAD BY LATER TUESDAY WITH THE SURFACE LOW AND NRN PORTION OF THE COLD FRONT. BEYOND TUE...AN UPPER TROUGH MOVING ACROSS THE NRN PLAINS TAKES OVER AND IMPACTS A COLD FRONT REACHING THE SOUTHEAST...DISCUSSED IN THE NEXT SECTION. 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 ECMWF/CMC CONFIDENCE: A LITTLE BELOW AVERAGE THE 00Z NAM AND 00Z UKMET ARE TOWARD THE SLOWER SIDE WITH THE EVENTUAL LONG WAVE TROUGH THAT FORMS OVER THE CNTRL PLAINS WED AND THE ASSOCIATED COLD FRONT WORKING EWD...AND THE 00Z GFS IS ON THE FAST SIDE RELATIVE THE REMAINING MODEL GUIDANCE. THE SREF/GEFS/EC MEANS SUGGEST THE GFS IS TOO WEAK WITH A SOUTHEAST UPPER RIDGE WHICH ALLOWS THE COLD FRONT TO MORE QUICKLY PROGRESS SOUTH AND EAST. THE ECMWF TRENDED SLOWER SINCE FOUR CYCLES AGO AND HAS BEEN RATHER STEADY WITH ITS LAST TWO CYCLES. CURRENT ENSEMBLE MEANS SUPPORT A FASTER SOLUTION THAN THE SLOWER NAM/UKMET BUT ENSEMBLE SPREAD REMAINS LARGE WHICH LOWERS CONFIDENCE AND PREFER TO STAY TOWARD THE MIDDLE TO SLOWER END OF THE GUIDANCE AT THIS TIME. SECONDARY SHORTWAVE ENERGY DIVING SOUTH OFF CALIFORNIA TODAY CROSSING BACK INTO SOUTHWEST STATES LATE TUESDAY ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 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. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... OTTO