Prognostic Meteorological Discussion
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000
FXUS10 KWNH 210404
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1203 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 AND GFS


...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 12Z 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 12Z 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 12Z ECMWF...THROUGH 72 HRS
            12Z ECMWF...72 HRS TO 84 HRS
CONFIDENCE: AVERAGE

THE 12Z GEM IS GENERALLY THE FASTEST WITH THE HEIGHT FALLS THAT
DIG INTO THE WESTERN U.S. OVER THE NEXT FEW DAYS AND BEFORE THEN
ADVANCING OUT INTO THE NORTHERN PLAINS THIS WEEKEND.
CONSEQUENTLY...THE GEM DRIVES SFC LOW PRESSURE OVER THE CNTRL/NRN
PLAINS MORE QUICKLY OFF TO THE EAST AND TWD THE UPR MIDWEST BY
SUN. 12Z UKMET FOR ITS PART APPEARS TO BE A BIT OF A WEAK OUTLIER
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 12Z ECMWF UNTIL ABOUT 72 HRS
WHEN IT BECOMES A MORE AMPLIFIED WITH THE UPR TROUGH BY SUGGESTING
A NEG TILT...AND ALSO TUCKING SFC LOW PRESSURE FARTHER BACK TO THE
WEST OVER WRN ND. THE 12Z ECMWF HAS STRONGER ENSEMBLE SUPPORT WITH
THE GEFS MEAN AND ECENS MEAN. WILL FAVOR A BLEND OF THE 00Z GFS
AND 12Z ECMWF THROUGH 72 HRS...AND THEN THE 12Z 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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