Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
233 PM EDT Sun Mar 17 2019
Valid Mar 17/1200 UTC thru Mar 21/0000 UTC
...See NOUS42 KWNO (ADMNFD) for the status of the upper air
ingest...
12Z Model Evaluation Including Preferences and Confidence
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...Shortwave crossing the OH Valley/Mid-Atlantic thru Mon...
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Preference: General model blend
Confidence: Above average
The guidance shows very good mass field agreement with this system
as it advances east through the OH Valley today and tonight, and
then across the Mid-Atlantic region on Monday. A general model
blend will be preferred.
...Shortwaves dropping southeast across the Plains/Midwest...
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Preference: Blend of 12Z GFS/GEFS mean/UKMET
Confidence: Average
The models show multiple shortwave troughs dropping southeast from
southern Canada and down across the northern/central Plains and
adjacent areas of the Midwest. The 12Z GFS, 12Z UKMET and 12Z CMC
support a rather strong lead shortwave arrives across the northern
Plains by late Monday and digs southeast through the middle MS
Valley by early Wednesday and the TN Valley by Wednesday evening.
The 12Z NAM and 12Z ECMWF take the same shortwave down across the
northern/central Plains and then appear to struggle with how much
energy gets trapped underneath a blocking high over southwest
Canada and the northern High Plains. The 12Z ECMWF instead of a
consolidating a closed low near the central High Plains/Front
Range has now trended toward the 12Z NAM solution where it
elongates and stretches out the vorticity from the central High
Plains east across the middle MS/lower OH Valleys. There is
considerably stronger ensemble support for the more progressive
camp led by the GFS and UKMET. The CMC for its part is progressive
but not to the extent of the UKMET and GFS. The CMC also tends to
have a better defined closed low evolution that the remaining
guidance does not support.
Meanwhile, a second shortwave by Wednesday will be dropping down
across the Great Lakes region, and in this case, the GFS and UKMET
are a bit sharper with the trough versus the NAM, CMC and ECMWF.
There is a bit better ensemble support for the sharper trough, at
least from the GEFS mean. And based on the trends/clustering of
solutions with both shortwaves, the model mass field preference
will be toward a blend of the 12Z GFS, 12Z GEFS mean and 12Z UKMET.
...Upper trough /closed low moving into CA by Wed...
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Preference: Non-NAM blend...led by the 12Z GFS/ECMWF
Confidence: Slightly above average
An upper trough will be digging into CA by Wednesday along with
likely development of a closed low. The 12Z NAM is the most
aggressive with its height falls, with the global models all a bit
weaker. There are some modest timing differences with the height
falls within the global model suite, but for now the preference
will be a non-NAM blend led by the 12Z GFS and 12Z ECMWF.
Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml
500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml
Orrison