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Model Diagnostics Discussion
 
(Caution: Version displayed is not the latest version. - Issued 1722Z Jan 25, 2020)
 
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Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
1222 PM EST Sat Jan 25 2020

Valid Jan 25/1200 UTC thru Jan 29/0000 UTC

...See NOUS42 KWNO (ADMNFD) for the status of the upper air
ingest...

12Z Model Evaluation with latest Preferences and Confidence
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

...Deep closed low moving across the Northeast through Sunday...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: General model blend
Confidence: Above average

Very good agreement persists in the evolution of a strong closed
low currently across the Ohio Valley lifting northeast slowly
through the weekend. The main core of this feature has good model
consensus that it will drift through New England by Sunday and
then over Atlantic Canada on Monday. The guidance at least through
Monday is agreeable such that a general model blend can be
preferred.


...Shortwave crossing the northern Plains through Sunday...
...Energy then digging through the Midwest/OH Valley on Monday...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: Non-NAM blend
Confidence: Above average

A shortwave currently over the northern High Plains will dive
southeast across the Midwest and be racing across the OH Valley by
late Monday. It will then reach the Mid-Atlantic coast Monday
night. The 12Z NAM is a stronger outlier with this system, and so
a non-NAM blend will be preferred.


...Shortwave crossing the Great Lakes late Monday...
...Dropping down across the OH Valley on Tuesday...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: Blend of the 12Z GFS/00Z CMC/00Z UKMET
Confidence: Average

In the wake of the shortwave on Monday, a new northern stream
shortwave will drop southeast and cross the OH Valley on Tuesday.
The 12Z NAM tends to be a bit strong with this system, but the 00Z
ECMWF appears to be too weak. Better model clustering resides with
the 12Z GFS/00Z CMC and 00Z UKMET, so a blend of these solutions
will be preferred.


...Split flow trough crossing the West coast on Sunday...
...Energy ejecting through the Southwest and Plains by Tuesday...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: 12Z NAM/GFS and 00Z ECMWF blend...northern stream
            Non-CMC blend...southern stream
Confidence: Slightly above average

The models all take a progressive split flow trough across the
West Coast on Sunday, with a southern stream portion of the energy
then dropping down across the Southwest and amplifying into a
closed low as it approaches the southern High Plains by early
Tuesday. Meanwhile, the northern stream component of the trough
will be over the northern High Plains. The 00Z CMC is an outlier
with both northern and southern stream components as it is likely
too strong/slow and too far north with the southern stream energy,
and too slow with the energy in the northern stream. The 00Z UKMET
also appears to be too slow/deep with its handling of the northern
stream energy. A non-CMC blend will be preferred with the southern
stream evolution, and a NAM/GFS/ECMWF blend with the northern
stream evolution.


...Progressive upper trough over the Pacific Northwest Tuesday...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: Blend of the 12Z NAM and 00Z ECMWF
Confidence: Below average

Yet another in a series of Pacific shortwave troughs will arrive
on Tuesday across the Pacific Northwest. The 12Z GFS, 00Z CMC and
00Z UKMET are all deeper solutions with this system, and do have
some support for a relatively deeper solution from the GEFS
ensemble suite. The 12Z NAM and 00Z ECMWF solutions are weaker and
have better support from the CMCE/ECENS suites. So, will prefer
the relatively weaker consensus for now, but with limited
confidence.


Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml
500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml

Orrison