Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
234 AM EST Sun Jan 26 2020
Valid Jan 26/0000 UTC thru Jan 29/1200 UTC
...See NOUS42 KWNO (ADMNFD) for the status of the upper air
00Z Model Evaluation with Final Preferences and Confidence
...Deep closed low moving across the Northeast through Sunday...
Preference: Non-NAM blend
Confidence: Above average
Outside of the 00Z NAM which lags west of the consensus, the
global models are in very good agreement with the strong upper low
moving into Canada Monday and then opening before ejecting towards
...Shortwave digging from the Northern Plains today to off the
Mid-Atlantic coast Tuesday...
Preference: General Model Blend
07Z Update: The discrepancy between the NCEP and Non-NCEP camps
from the prior solutions has mostly disappeared, leaving good
consensus among the global suite. A general model blend is usable.
A sharp shortwave dropping through the Northern Plains will dive
quickly southeast and round the base of the longwave trough
centered over New England. This feature will move quickly through
the Ohio Valley and be off the Mid-Atlantic coast by Tuesday. The
CMC is a fast/sheared outlier compared to the remaining guidance
and should not be included. Of the remaining models, there exists
an NCEP vs Non-NCEP camp as the NCEP models are a bit stronger and
faster than the Non-NCEP solutions. The ECENS and GEFS are more in
line with the slower solutions, so favor the Non-NCEP camp for
this feature as it shifts east through early in the week.
...Trough lifting into the West today and deepening across the
Southern Plains by Tuesday...
Preference: Non-CMC/UKMET blend
Confidence: Slightly below average
07Z Update: While the overall evolution is pretty consistent and
agreed upon by the global models, some discrepancies are
increasing with the northern stream portion of the energy by day
2. The CMC and UKMET feature significantly more interaction of the
northern and southern streams, while the remaining guidance keep
these features separated with little interaction through 84 hours.
The GFS is on the weak side of the envelope with the southern
stream energy, but is well positioned otherwise so can still be
included but potentially with somewhat less weight than the
ECMWF/NAM and the means.
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. The 12Z CMC is an outlier as it is likely too strong/slow
and too far north with the southern stream energy. The 12Z UKMET
also appears to be too slow/deep and like the CMC tends to support
a bit more interaction between northern and southern stream
troughs late in the period. The NAM/GFS and ECMWF all favor a bit
more stream separation at least through this period with just some
subtle northern/southern stream trough interaction at the very end
of the period as the energy approaches the MS Valley. Will prefer
a blend of the NAM/GFS and ECMWF at this time given they still
tend to have the stronger ensemble support.
...Trough moving onshore the West Tuesday...
Preference: Blend of ECENS/GEFS means
Yet another in a series of Pacific shortwave troughs will arrive
on Tuesday across the Pacific Northwest. There is considerable
spread in intensity of this feature despite reasonable agreement
in timing on D3. The ensemble means are in generally good
agreement and are favored outside of any operational model which
show a wide variation in solutions in the fast mid/upper flow.
Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml
500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml