Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
245 PM EDT Tue May 21 2019

Valid May 21/1200 UTC thru May 25/0000 UTC

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

12Z Model Evaluation...with Preferences and Confidence...
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...Deep layer low/trough over the Central U.S...
...Reaching the Northeast on Friday...
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Preference: General model blend
Confidence: Above average

The 12Z models are in better agreement compared to the 00Z/06Z
cycles and support the deep layer closed low over the central U.S.
lifting off to the northeast through the upper Midwest and Great
Lakes region through Wednesday and Thursday. The energy though is
expected to then advance east and southeast down across the
Northeast on Friday as the entire system rounds the top of a
strong subtropical ridge developing over the Gulf Coast states and
Southeast through the period. The 12Z UKMET may still be a tad too
deep with its height falls involving the Northeast on Friday, by
the differences compared to the other models are very modest, so
at this point, a general model blend will be preferred.


...Vigorous Pacific closed low digging into the West...
...Lifting across the Northern Plains by Friday...
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Preference: General model blend
Confidence: Above average

There is good agreement with the next deep layer closed low that
drops down across the West through Thursday and then lifts
northeast across the northern Plains on Friday. The 12Z ECMWF may
be a tad too strong with its height falls crossing the northern
Plains on Friday, but for the time being a general model blend
should suffice with this mass field evolution.


...Closed low/trough over the Pacific Northwest on Friday...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: Blend of the 12Z NAM/GFS/ECMWF
Confidence: Above average

All of the models agree in dropping yet another upper trough and
associated closed low down into the Pacific Northwest on Friday.
The 12Z UKMET is a bit weaker and more progressive than the rest
of the guidance as the energy drops inland. The rest of the
guidance is well clustered with depth, but the 12Z CMC does appear
to be perhaps a little too slow. Will prefer a blend of the NAM,
GFS and ECMWF at this point given their degree of
agreement/clustering.


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

Orrison