Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
327 PM EDT Mon May 04 2020
Valid May 04/1200 UTC thru May 08/0000 UTC
...See NOUS42 KWNO (ADMSDM) for the status of the upper air
ingest...
12Z Final Model Evaluation Including Preferences and Confidence
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...Series of impulses on a pair of mid-level shortwaves tracking
across the northern/central Great Plains and the Ohio Valley
through Tuesday night...
...These waves consolidate over the Mid-Atlantic Wednesday and
track off New England Thursday...
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Preference: Non-NAM General Model Blend...less weight for 12Z GFS
on Day 2 and the 12Z ECMWF on Day 3
Confidence: Average
Convective complexes over Missouri are ahead of a mid-level wave
over the central Great Plains which will be reinforced by energy
coming from a low over the western Canadian Prairies as the
features shift to the Ohio Valley through Tuesday night. A surface
low will develop from the Missouri complex over the Mid-South
tonight and track east southern Appalachians Tuesday before a
coastal low develops along the Carolina Coast Tuesday night. The
overall pattern of the surface low track and coastal development
is in decent agreement and a general model blend is preferred
through Tuesday/Day 1.
As a surface low develops and shifts north off the Mid-Atlantic
Wednesday differences in track arise. The 12Z ECMWF remains
farthest east, particularly Wednesday night and on while the 12Z
UKMET/CMC shifted west and are a good compromise between the ECMWF
and the farther west 12Z GFS. The 12Z GFS is the quickest to
develop, closing off at 500mb Tuesday night which allows a farther
north track that comes into better alignment by Wednesday night.
The 12Z NAM, however, tracks farther south from the Carolinas and
is slower to develop/weaker and is enough of an outlier to be
dismissed from the preference.
...Shortwave trough brushing Pacific Northwest coast tonight...
...Mid-level shortwave moving from Pacific Northwest Coast Tuesday
night across the northern Rockies Wednesday night and the northern
Plains Thursday...
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Preference: 12Z GFS/ECMWF/UKMET
Confidence: Slightly Above Average
A shortwave trough will pivot around a broad upper level gyre over
the Gulf of Alaska and clip the Pacific Northwest coast tonight.
There are no outliers with this feature.
The next shortwave trough is much stronger/amplified as it crosses
the WA/OR coast Tuesday night and the ID/MT Rockies Wednesday
night. There is little difference among guidance here as the
trough takes on a negative tilt and closes off into a low over MT.
The 12Z ECMWF/GFS are in excellent agreement (along with their Day
2/3 QPF), so they are preferred. The 12Z UKMET inched north and
into agreement with the ECMWF/GFS. The 12Z NAM is slightly south
and the 12Z CMC remains even farther south. The 12Z UKMET remains
slightly weaker with less of a closed low, but the track agreement
warrants its inclusion in the preference.
Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml
500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml
Jackson