Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
1144 AM EST Sun Jan 26 2020
Valid Jan 26/1200 UTC thru Jan 30/0000 UTC
...See NOUS42 KWNO (ADMNFD) for the status of the upper air
12Z Model Evaluation with latest Preferences and Confidence
...Shortwaves crossing the Great Lakes/OH Valley through Tuesday...
Preference: General model blend
Confidence: Above average
A shortwave currently digging southeast over the Midwest will race
across the OH Valley by late Monday. It will then reach the
Mid-Atlantic coast Monday night. In its wake, a second shortwave
will also be dropping down from the Great Lakes region which will
cross the OH Valley through Tuesday. The 12Z NAM occasionally
appears to be perhaps a tad too strong, but the overall model
spread is quite minimal, so a general model blend will be
...Split flow trough crossing the West coast today...
...Energy ejecting through the Southwest and Plains by Tuesday...
Preference: Blend of the 12Z GFS/06Z GEFS/00Z ECMWF/00Z ECENS mean
Confidence: Below average
The models all take a progressive split-flow trough across the
West today, 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 by early Tuesday. The 00Z CMC
remains a bit out of tolerance with the 12Z NAM/GFS solutions and
the remaining 00Z non-NCEP models concerning both streams, and
again suggests a surface low evolving over the southern
Plains/lower MS Valley that tracks a bit north of the model
consensus. The 12Z GFS suggests a somewhat more amplified southern
stream evolution, with a relatively stronger surface low that
crosses the lower MS Valley by early Wednesday. The 12Z NAM in
time becomes the slowest solution, and the weakest with its
surface reflection. The 00Z UKMET is also weak, but is more
progressive. The differences with the northern stream energy are
not as vast, but the NAM and ECMWF may be too amplified with this
energy. Given the deterministic model spread with timing/depth of
the energy crossing especially the southern U.S., the preference
at this point will be to blend the latest GEFS/ECENS means and the
12Z GFS/00Z ECMWF solutions as a means of approximating the model
consensus for both the northern and southern streams.
...Progressive upper trough over the Pacific Northwest Tuesday...
...Amplifying into the West on Wednesday...
Preference: Non-NAM blend
Yet another in a series of Pacific shortwave troughs will arrive
on Tuesday across the Pacific Northwest, and then dig into the
West on Wednesday, with the gradual development of a closed low
over the Southwest late Wednesday. The 12Z NAM may be a tad too
weak and fast as the energy initially comes into the Pacific
Northwest, but then by late Wednesday appears to be a little too
slow with its height falls pivoting toward the Southwest. The
global models are overall in pretty good agreement with the larger
scale mass field evolution, so a non-NAM blend will be preferred
with this system for the time being.
Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml
500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml