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FXUS10 KWNH 211844
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
243 PM EDT THU AUG 21 2014

VALID AUG 21/1200 UTC THRU AUG 25/0000 UTC

...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR
INGEST...

12Z MODEL EVALUATION...INCLUDING PRELIMINARY PREFERENCES
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

UPPER TROUGHING MOVING FROM THE GREAT LAKES ACROSS THE NORTHEAST
COLD FRONT SINKING SWD THROUGH THE EAST COAST STATES
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: BLEND OF THE 12Z ECMWF/UKMET/CMC
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

THE 12Z 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 REMAINING
DETERMINISTIC MODEL CONSENSUS IS WEAKER WITH MID-LEVEL HEIGHTS
OVER THE WRN ATLANTIC BUT THE LATEST GEFS/EC MEANS SUPPORT A
LITTLE BIT OF A DEEPER UPPER TROUGH THAN DEPICTED BY THE 12Z GFS
AND THE 12Z ECMWF TO SOME DEGREE. A BLEND OF THE 12Z ECMWF WITH
THE 12Z UKMET/CMC HAVE GOOD SUPPORT FROM THE MEANS AND SHOW A GOOD
MIDDLE OF THE ROAD COMPROMISE WITH THE UPPER TROUGH AND
CORRESPONDING COLD FRONT THROUGH THE SOUTHEAST COAST.


WEAKENING MID-LEVEL DISTURBANCE LIFTING NEWD FROM THE SOUTHWEST
LOW PRESSURE DEVELOPING OVER THE CENTRAL/NORTHERN PLAINS
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: BLEND OF THE 12Z ECMWF/UKMET/CMC
CONFIDENCE: SLIGHTLY ABOVE AVERAGE

THE 12Z NAM IS SOMEWHAT OF A STRONGER OUTLIER WITH THE ENERGY THAT
EJECTS NEWD OUT OF THE SOUTHWEST OVER THE NEXT COUPLE OF DAYS AND
AHEAD OF THE LARGER SCALE UPPER TROUGH/CLOSED LOW THAT DIGS SEWD
INTO THE NWRN U.S. BY THIS WEEKEND. THE STRONGER NAM ALSO DEPICTS
A MUCH STRONGER SURFACE LOW TRACKING THROUGH THE DAKOTAS SAT NIGHT
INTO MINNESOTA BY EARLY SUN. THE 12Z ECMWF/UKMET/CMC HAVE COME IN
WITH MUCH BETTER AGREEMENT TO EACH OTHER AND SUGGEST THE 12Z GFS
COULD BE A LITTLE WEAK. THEREFORE...THE PREFERENCE IS TO ADJUST
TOWARD THE STRONGER ECMWF/UKMET/CMC WHICH ALSO SHOW GOOD AGREEMENT
WITH THE LATEST ENSEMBLE MEANS.


UPPER TROUGHING/CLOSED LOW DIGGING INTO THE WESTERN U.S. FOR FRI
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: BLEND OF THE 12Z ECMWF/UKMET/CMC
CONFIDENCE: AVERAGE

SOMEWHAT TIED TO THE SECTION ABOVE...THE BLENDED 12Z
ECMWF/UKMET/CMC APPEARS TO BE THE BEST COMPROMISE HERE. MODEL
SPREAD IS GREATEST BY SUN MORNING WITH A LARGE SCALE UPPER TROUGH
FORMING OVER THE NORTHWEST CONUS. THE 12Z ECMWF/UKMET/CMC ARE IN
GOOD AGREEMENT AND HAVE BETTER AGREEMENT TO THE ENSEMBLE MEANS
COMPARED TO THE 12Z GFS...SO THE 12Z GFS HAS BEEN TAKEN OUT OF THE
PREFERENCE. THE 12Z ECMWF HAS ALSO ADJUSTED WEAKER...AND TOWARD
THE REMAINING MODEL CONSENSUS...WITH A SECONDARY SHORTWAVE DIGGING
TOWARD THE PACIFIC NORTHWEST BY SUN EVENING.


...MODEL TREND GRAPHICS AT
www.wpc.ncep.noaa.gov/html/model2.shtml...
...500 MB FORECASTS AT
www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml...

OTTO

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