Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
129 PM EST Tue Jan 07 2020
Valid Jan 07/1200 UTC thru Jan 11/0000 UTC
...See NOUS42 KWNO (ADMNFD) for the status of the upper air
ingest...
12Z Model Evaluation with Preferences and Confidence
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...Surface low impacting the Mid-Atlantic/Northeast Today...
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Preference: General model blend
Confidence: Above average
1830Z update: No significant changes noted with the rest of the
12Z guidance and will still lean on a general model blend
preference.
A compact, progressive shortwave trough currently advancing toward
the Mid-Atlantic will move offshore later tonight. A weak area of
low pressure currently analyzed over western NC is well agreed
upon by the latest guidance. The low track clusters are tightly
packed and any differences lie in the mesoscale, boundary layer
and a general model blend is preferred.
...Northern stream trough crossing the Northeast by Wed...
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Preference: General model blend
Confidence: Above average
1830Z update: No significant changes noted with the rest of the
12Z guidance and will still lean on a general model blend
preference.
The models advance a northern stream upper trough and attendant
cold front across the Great Lakes today, and then through the
Northeast on Wednesday. Very good model agreement continues to be
seen in the early 12Z guidance and older 00Z such that a general
model blend remains the preference.
...Parade of shortwaves crossing the Pacific Northwest...
...Energy advancing east across the Plains/Midwest...
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Preference: Non-NAM, non-CMC blend
Confidence: Average
1830Z update: The NAM remains on the slower end of the model
spread and the GFS now is clearly on the faster side of the
solutions with the rest of the 12Z guidance now available with the
shortwave trough entering the Pacific NW and CA coast Thursday. As
this wave quickly dives toward the Southwest US the differences
seem to resolve themselves with just some typical timing biases.
With the second system moving into the region late Friday into the
weekend, overall model guidance is fairly good for Day 3, with the
UKMET surface low track a bit behind the rest of the guidance.
A series of shortwaves and impulses are forecast to impact the
Pacific Northwest over the next 3 days as generally a trough west,
ridge east pattern remains in place. The CMC is the initial
outlier with its slower timing as well further south. The 12Z GFS
is usable, though at 500 mb, its shortwave a bit more amplified
than what the NAM or other guidance shows. The 12Z GFS is also
faster than a lot of guidance and is way ahead of its ensemble
mean. So while the preference is for a ECMWF/UKMET/GFS blend,
higher weight is given toward the ECMWF/UKMET at this time.
Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml
500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml
Taylor