Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
331 PM EDT Tue Mar 19 2019
Valid Mar 19/1200 UTC thru Mar 23/0000 UTC
...See NOUS42 KWNO (ADMNFD) for the status of the upper air
ingest...
12Z Model Evaluation Including Preferences and Confidence
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...Trough and Developing Low in the East...
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Preference: Blend of 12Z GFS/ECMWF/NAM
Confidence: Average
Considerable model spread persists through Day 3 with guidance
still shifting the track of the coastal low expected to develop
off the Mid-Atlantic Wednesday night and move over the Northeast
through Friday. Both the operational 12Z ECMWF and 12Z GFS trended
slower and farther inland compared to the previous run. The 12Z
ECMWF is still farther inland than the 12Z GFS, particularly into
Day 3, and is similar to the 12Z NAM. However, notable spread in
both the 12Z GEFS and 00Z ECENS suggest uncertainty persists and
further shifting of the track can be expected. Given the continued
inland trend of the ECMWF and its similarity to the NAM, the
preference will now include the 12Z NAM.
The track of this low is sensitive to northern stream shortwaves
that will be interacting, including a phase on Thursday and of
particular concern is the reinforcing shortwave that reaches the
Great Lakes Thursday night which will influence the track of the
primary trough/low through Friday and where the phasing takes
place over the weekend (beyond the current Day 3 outlook). The 12Z
ECMWF slowed both features with this run, so the reinforcing
northern stream shortwave is now technically slow in the 12Z ECMWF
than the 12Z GFS, but the slower leading trough has shifted the
track farther inland in the ECMWF than the GFS. The intensity of
the components are similar among the 12Z GFS, ECMWF, and NAM
resulting in similar QPF magnitude. The 12Z UKMET and CMC made
considerable shifts in their surface low track closer to the
guidance consensus, but remain considerable outliers. The
preference has been updated to include the NAM with the GFS/ECMWF
and the caveat that much is still to be determined with the timing
and intensity of the interacting components of this low is still
relevant.
...Low and approaching trough in the West...
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Preference: General Model Blend
Confidence: Above Average
An amplified/full-latitude trough currently off the West Coast
comes ashore tonight before closing into a low over the Desert SW
Thursday and swinging into the northern Rockies through Friday.
Excellent agreement is seen with the mid/upper portions of the
system among 12Z global guidance with this feature, so a general
model blend is recommended.
The next trough approaches the West Coast late Friday with good
timing agreement among 12Z global guidance with the arrival of QPF
into CA. A general model blend also holds for this second feature.
Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml
500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml
Jackson