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FXUS10 KWNH 211654
PMDHMD

MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1254 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 NAM/GFS 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 00Z ECMWF/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 06Z GEFS AND 00Z EC MEANS SUPPORT A
LITTLE BIT OF A DEEPER UPPER TROUGH THAN DEPICTED BY MUCH OF THE
NON NAM GUIDANCE. GIVEN THE 00Z CMC AND ECMWF ARE BOTH SLIGHTLY
DEEPER AND IN A FAVORABLE POSITION WITH THE COLD FRONT THROUGH THE
SOUTHEAST COAST...THE PREFERENCE IS TO STAY WEAKER THAN THE
NAM...BUT TOWARD THE STRONGER SIDE OF THE REMAINING DETERMINISTIC
GUIDANCE...CLOSEST TO THE 00Z ECMWF/CMC.


WEAKENING MID-LEVEL DISTURBANCE LIFTING NEWD FROM THE SOUTHWEST
LOW PRESSURE DEVELOPING OVER THE CENTRAL/NORTHERN PLAINS
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: BLEND OF THE 12Z GFS / 00Z ECMWF
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. GIVEN THE 00Z CMC IS A BIT MORE
PROGRESSIVE WITH THE UPSTREAM TROUGH ACROSS THE NORTHWEST...IT HAS
A SURFACE LOW DISPLACED EWD ACROSS THE N-CNTRL U.S. SO A BLEND OF
THE 12Z GFS AND 00Z ECMWF APPEARS THE BEST COMPROMISE AT THE
MOMENT.


UPPER TROUGHING/CLOSED LOW DIGGING INTO THE WESTERN U.S. FOR FRI
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: BLEND OF THE 12Z GFS / 00Z ECMWF
CONFIDENCE: AVERAGE

SOMEWHAT TIED TO THE SECTION ABOVE...THE GFS/ECMWF COMBO APPEAR 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 00Z CMC IS MORE PROGRESSIVE WITH THIS FEATURE WHILE THE
12Z NAM IS NOT FAVORED UPSTREAM...AND THE 00Z UKMET A BIT SOUTH OF
THE GFS/ECMWF AND ENSEMBLE MEANS REGARDING THE 500 MB LOW CENTER.
WHILE THE 00Z ECMWF IS PROBABLY TOO STRONG WITH A SECONDARY
SHORTWAVE DIGGING INTO THE PACIFIC NORTHWEST BY SUN EVENING...WHEN
BLENDED WITH THE WEAKER GFS...THE IMPACTS TO THE LOWER 48 FROM THE
ECMWF ARE REDUCED.


...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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