Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
257 AM EDT Sat May 09 2020
Valid May 09/0000 UTC thru May 12/1200 UTC
...See NOUS42 KWNO (ADMSDM) for the status of the upper air
ingest...
00Z Model Final Evaluation Including Latest Preferences and
Confidence
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...Deepening surface low moving along the Northeast Coast...
...Dual Shortwaves moving out of Canada and around periphery of
Eastern North American Low
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Preference: Non-CMC blend
Confidence: Above average
Flow over North America is expected to feature an omega block with
lows near 45N/145W and over the Northeast U.S. and adjacent
portions of Canada...with a ridge extending from the Western U.S.
northward across western Canada as far north as the Yukon and
Northwest Territories.
The models have a decent handle on the large-scale pattern. The
agreement persists as far down into the details of the Northeast
U.S. low being anomalously deep (by nearly 4 standardized
anomalies greater than climatology) and magnitude of an
anomalously strong mid- and upper-level jet will be supporting the
low. The 09/00Z NCEP guidance remained in good agreement with the
08/12Z ECMWF and UKMET with respect to the low as well as in
regards to two shortwaves that drop out of Canada in succession
within northerly flow between the ridge to the west and the low to
the east...and then rotating around the periphery of the broader
circulation of the low on Sunday and Monday as it makes its way
toward Labrador. There are some difference with respect to timing
and the degree to which the shortwaves can interact and sharpen a
broader trough. In this case, think a non-Canadian blend will work
to minimize some of the timing differences. A second shortwave
which initially begins north of Hudson Bay on Sunday may be too
strong at 500 mb in the 09/00Z ECMWF by the time it reaches the
northern Great Lakes late Monday.
...Shortwave energy crossing southern CA by Sun morning...
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Preference: General model blend
Confidence: Above average
A weak shortwave lifting onshore southern CA Saturday will weaken
as it shifts eastward into the Desert Southwest on Sunday. The
overall envelope of solutions remains minimal..and a general model
blend should minimize what differences in timing and magnitude
there are.
Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml
500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml
Bann