698
FXUS10 KWNH 110432
PMDHMD
MODEL DIAGNOSTIC DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1231 AM EDT TUE AUG 11 2020
VALID AUG 11/0000 UTC THRU AUG 14/1200 UTC
...SEE NOUS42 KWNO (ADMSDM) FOR THE STATUS OF THE UPPER AIR
INGEST...
00Z NAM/GFS EVALUATION INCLUDING PRELIMINARY PREFERENCES AND
FORECAST CONFIDENCE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
...LONGWAVE TROUGHING OVER THE NORTHWEST TO THE NORTHERN PLAINS
TUESDAY THROUGH THURSDAY...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: BLEND OF 12Z ECMWF/18Z GEFS MEAN
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
DURING TUESDAY THROUGH THURSDAY, THE MODEL CONSENSUS IS FOR A
LONGWAVE TROUGH TO AMPLIFY ACROSS THE PACIFIC NORTHWEST INTO
NORTHERN CA. LOW AMPLITUDE SHORTWAVES EJECT AND MOVE EAST
NORTHEAST ACROSS THE NORTHERN ROCKIES AND NORTHERN PLAINS. ON THU
NIGHT THE MODELS SHIFT THE TROUGH AXIS EAST ACROSS THE NORTHERN
ROCKIES AND HIGH PLAINS. MINOR TIMING DIFFERENCES DEVELOP, WITH
THE OPERATIONAL GFS FASTER THAN OTHER MODELS. AS USUAL, THE GEFS
MEAN HAD SLOWER FORWARD PROGRESSION THAN THE OPERATIONAL GFS AND
IS PREFERRED, GIVEN THE GFS BIAS OF MOVING LONGWAVE TROUGHS TOO
QUICKLY.
MID TO UPPER MS VALLEY
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: BLEND OF ECMWF/00Z GFS
CONFIDENCE: AVERAGE
THE DIFFERENCES NOTED WERE THE 12Z UKMET/CMC/00Z NAM SHOWED
CONVECTIVELY GENERATED VORTICITY MAXIMA THAT RESULTED IN
POTENTIALLY SPURIOUS CLOSED LOWS WITHIN PROGRESSIVE WAVES EJECTING
NORTHEAST ACROSS THE UPPER MS VALLEY. THE 00Z GFS ALLOWED FOR A
LESS DEVELOPED AND FASTER MOVING LOW, WHICH APPEARS TO BE A TREND
ON THE RIGHT DIRECTION.
SOUTHEAST TO MID ATLANTIC
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PREFERENCE: BLEND OF ECMWF/21Z SREF MEAN
CONFIDENCE: SLIGHTLY ABOVE AVERAGE
THE MODELS SHOW A HIGH AMPLITUDE RIDGE OVER THE WESTERN ATLANTIC
THAT KEEPS A MID LEVEL TROUGH OVER THE EASTERN CAROLINAS AND
GEORGIA IN PLACE OR DRIFTING SLOWLY. THIS RESULTS IN INCREASED
AGREEMENT OVER PRIOR FORECASTS. WITH GOOD AGREEMENT AMONG THE
ECMWF AND GFS, ALONG WITH THE ENSEMBLE MEANS OF THE 21Z SREF/12Z
ECMWF MEAN, AND 18Z GEFS MEAN, A CONSENSUS OF THESE SOLUTIONS
WOULD RESOLVE MINOR TIMING/AMPLITUDE DIFFERENCES.
MODEL TRENDS AT WWW.WPC.NCEP.NOAA.GOV/HTML/MODEL2.SHTML
500 MB FORECASTS AT WWW.WPC.NCEP.NOAA.GOV/H5PREF/H5PREF.SHTML
THIS PRODUCT WILL TERMINATE AUGUST 15, 2020:
WWW.WEATHER.GOV/MEDIA/NOTIFICATION/PDF2/SCN20-58PMDHMD_TERMINATION.
PETERSEN
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