Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
1213 PM EDT Thu Mar 14 2019
Valid Mar 14/1200 UTC thru Mar 18/0000 UTC
...See NOUS42 KWNO (ADMNFD) for the status of the upper air
ingest...
12Z Model Evaluation Including Preferences and Confidence
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
...Powerful deep closed low exiting the Midwest/Great Lakes...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: General model blend
Confidence: Above average
The models show very good agreement in taking the deep layer
closed low over the Midwest northeast across the Great Lakes
tonight and then across southeast Canada on Friday. Meanwhile, a
trailing cold front will sweep across the eastern U.S. with the
front moving off the East Coast Friday night with exception of the
lower part of the FL Peninsula where the boundary is expected to
slow down and only gradually shift south. Given very good model
mass field agreement, a general model blend will be preferred.
...Shortwave energy over the northern Plains/Midwest...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: Non-NAM blend
Confidence: Slightly above average
In the wake of the exiting deep cyclone over the Midwest and Great
Lakes will be an intrusion of northern stream shortwaves from
southern Canada which will cross the northern Plains and Midwest
through the weekend. The 12Z NAM is overall a bit sharper with the
shortwave impulses and consequently drives a bit heavier QPF
versus the global models. Will recommend a non-NAM blend at this
point given the reasonably good global model mass field agreement.
...Weak upper trough reaching the West Coast tonight...
...Digging into the Southwest on Fri/Sat...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: Non-ECMWF blend
Confidence: Above average
A weak upper trough will approach the West Coast by tonight and
then separate out from the westerlies and dig into the Southwest
on Friday and Saturday. The guidance agrees in developing a weak
closed low feature over AZ by early Saturday, with the closed low
then gradually elongating and shifting off to the east across
portions of NM through Sunday. The 00Z ECMWF is overall the
deepest solution with the closed low, and especially by Sunday. As
a result, the ECMWF is also a bit wetter than the remaining
guidance. Given reasonably good model mass field agreement seen
otherwise, a non-ECMWF blend will be preferred.
...Shortwave over the northern Rockies by Sun...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: Non-GFS blend
Confidence: Above average
The 12Z GFS is a stronger outlier with the shortwave rounding the
mean layer ridge along the West Coast on Sunday and dropping down
over the northern Rockies. The remaining guidance is rather well
clustered, so a non-GFS blend will be preferred.
Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml
500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml
Orrison