Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
1208 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/06Z GEFS mean/00Z 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, 00Z UKMET and 00Z 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 00Z 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 ECMWF
consolidates a closed low near the central High Plains/Front Range
by Wednesday whereas the NAM 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 also supports a stronger
closed low evolution over the mid MS Valley that is not well
supported at this time.
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, 06Z GEFS mean and 00Z UKMET.
...Upper trough /closed low moving into CA by Wed...
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Preference: Non-NAM blend...led by the 12Z GFS/00Z 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 00Z 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