Prognostic Meteorological Discussion
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000 FXUS10 KWNH 210629 PMDHMD MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 228 AM EDT THU AUG 21 2014 VALID AUG 21/0000 UTC THRU AUG 24/1200 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 00Z MODEL EVALUATION...INCLUDING THE NAM/GFS/UKMET/GEM AND ECMWF ...UPPER TROUGHING MOVING FROM THE GREAT LAKES ACROSS THE NORTHEAST... ...COLD FRONT SINKING SWD THROUGH THE EAST COAST STATES... PREFERENCE: BLEND OF THE 00Z GFS AND 00Z ECMWF CONFIDENCE: ABOVE AVERAGE THE 00Z NAM ENDS UP ON THE DEEPER END OF THE GUIDANCE CONCERNING THE 500 MB TROUGH EVOLVING IN THE WRN ATLANTIC BY THIS WEEKEND WHICH CAUSES THE NAM TO BE ON THE SOUTH SIDE WITH A COLD FRONT THAT SETTLES SOUTH INTO THE SERN STATES. THE 00Z GFS AND 00Z ECMWF WILL CONTINUE TO BE FAVORED IN KEEPING WITH CONTINUITY AND THESE MODELS ARE WELL CLUSTERED. ...WEAKENING MID-LEVEL DISTURBANCE LIFTING NEWD FROM THE SOUTHWEST... PREFERENCE: NON-NAM COMPROMISE CONFIDENCE: ABOVE AVERAGE THE 00Z NAM IS SOMEWHAT OF A STRONGER OUTLIER WITH THE ENERGY THAT EJECTS NEWD OUT OF THE SOUTHWEST THE NEXT COUPLE OF DAYS AND AHEAD OF THE LARGER SCALE TROUGH/CLOSED LOW THAT DIGS SWD INTO THE WESTERN U.S. BY THIS WEEKEND. WILL FAVOR A NON-NAM COMPROMISE AS A RESULT...ESP AS THE REMAINING GLOBAL MODELS ARE REASONABLY WELL CLUSTERED WITH THEIR MASS FIELDS. ...UPPER TROUGHING/CLOSED LOW DIGGING INTO THE WESTERN U.S... ...LOW PRESSURE DEVELOPING OVER THE CENTRAL/NORTHERN PLAINS... PREFERENCE: BLEND OF THE 00Z GFS AND 00Z ECMWF...THROUGH 72 HRS 00Z ECMWF...72 HRS TO 84 HRS CONFIDENCE: AVERAGE THE MODELS ARE IN GOOD AGREEMENT ON AMPLIFYING AN UPR TROUGH OVER THE WESTERN U.S. THE NEXT COUPLE OF DAYS WITH THE ENERGY THEN ENCROACHING ON THE NRN HIGH PLAINS BY SUN. A COMBINATION OF THIS AND LEAD SHORTWAVE ENERGY EJECTING NEWD OUT OF THE SOUTHWEST WILL ALSO HELP TO DRIVE SFC LOW PRESSURE OVER THE CNTRL AND NRN PLAINS. THE 00Z GEM HAS TRENDED A LITTLE SLOWER WITH ITS HEIGHT FALL EVOLUTION...BUT IS STILL A LITTLE MORE PROGRESSIVE WITH ITS SFC LOW EVOLUTION OVER THE PLAINS AND TWD THE UPR MIDWEST THROUGH THE PERIOD. THE GEM IS ALSO A TAD WEAKER THAN THE MODEL CONSENSUS ALOFT. THE 00Z UKMET HAS ALSO TRENDED A LITTLE SLOWER AND IS RATHER CLOSE TO THE GLOBAL MODEL CONSENSUS ALOFT. THE 00Z NAM IS THE MOST AMPLIFIED SOLN ALOFT AND ESP AT THE SFC WITH ITS LOW CENTER LIFTING NWD THROUGH THE NRN PLAINS. THE 00Z GFS IS WELL CLUSTERED WITH THE 00Z ECMWF UNTIL ABOUT 72 HRS WHEN IT BECOMES MORE AMPLIFIED WITH THE UPR TROUGH BY SUGGESTING A NEG TILT...AND ALSO TUCKING A STRONGER SFC LOW FARTHER BACK TO THE WEST OVER WRN ND. THE 00Z ECMWF HAS STRONGER ENSEMBLE SUPPORT WITH THE GEFS MEAN AND ECENS MEAN. WILL FAVOR A BLEND OF THE 00Z GFS AND 00Z ECMWF THROUGH 72 HRS...AND THEN THE 00Z ECMWF THEREAFTER. ...MODEL TREND GRAPHICS AT www.wpc.ncep.noaa.gov/html/model2.shtml... ...500 MB FORECASTS AT www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... ORRISON $$

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