Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
249 AM EDT Sun Aug 9 2020
Valid Aug 9/0000 UTC thru Aug 12/1200 UTC
...See NOUS42 KWNO (ADMSDM) for the status of the upper air
ingest...
00Z Model Evaluation Including Final Preferences and Forecast
Confidence
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Overall weather pattern across the continental U.S.
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Preference: General model blend through 18Z Monday, then
GFS/ECMWF/CMC blend
Confidence: Average
7Z update: Both the ECMWF and UKMET trended slightly more
amplified with the trough building in across the Pacific Northwest
by the middle of the week. The UKMET continues to be stronger
with the upper ridge across the eastern U.S. and is not in line
with the model consensus, which indicates a weak trough axis near
the East Coast. Otherwise, no major changes noted with the
arrival of the UKMET, CMC, and ECMWF.
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The overall weather pattern across the continental U.S. will be
quasi-zonal across the northern half of the continental U.S., with
a mid-level ridge anchored over the south-central U.S. The main
synoptic feature on the map will be a large mid-level closed low
tracking eastward across Canada, with a related cold front at the
surface forecast to move across the Great Lakes region. By the
end of the forecast period Wednesday morning, another trough
begins to build across the northwestern U.S. with height falls
arriving from the Gulf of Alaska.
The models show fairly good agreement regarding the
timing/strength of the closed low and a shortwave spoke rounding
the base of the closed low, tracking from Saskatchewan on Sunday
to western Ontario on Monday. The 00Z NAM is slightly more
amplified with this feature. A second closed low/shortwave is
forecast to enter western Canada on Tuesday and result in a
building trough across the Pacific Northwest and northern Rockies.
The latest guidance indicates only modest amplitude differences
with the second closed low, with the 00Z NAM farther east with the
trough axis and the 00Z GFS slightly stronger. Similar to
yesterday, the UKMET continues to indicate a stronger ridge across
the south-central U.S. and shows less southward progression with
the shortwave troughs. Taking these factors into account, a
general model blend can be incorporated through about 18Z Monday,
after which a GFS/ECMWF/CMC blend would offer a good starting
point in the forecast process.
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.
pdf
Hamrick