Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
324 PM EDT Mon Apr 06 2020
Valid Apr 06/1200 UTC thru Apr 10/0000 UTC
...See NOUS42 KWNO (ADMNFD) for the status of the upper air
ingest...
12Z Model Evaluation with Initial Preferences and Confidence
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Slow moving southern stream closed low.
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Preference: General model through 08.12Z; non-GFS, non-NAM blend
for day 3
Confidence: Slightly above average
19Z update: No significant changes with this system, the 12Z
non-NCEP guidance continues to advertise a slower progression of
the closed low into the southwest and this remains the preferred
approach.
---previous discussion---
Anomalous upper level closed low currently centered off the
California coast will drop to the south over the next couple of
days before moving inland toward the Four Corners region by the
end of day 3. Through 48 hours (08.12Z) there is very good
agreement in the upper level pattern in the latest deterministic
guidance. Beyond that time frame, there remains some progression
issues between the NCEP guidance (GFS/NAM) and non-NCEP
(UKMET/CMC/ECMWF). The latest 12Z GFS and NAM are faster to pull
the system eastward, opening up as there appears to be more
interaction with the digging northern stream energy over the
Plains and Great Lakes. Meanwhile, the ECMWF/CMC/UKMET offer a
slower solution, more separated from the northern stream energy.
The slower progression remains favored, as it appears the
deterministic GFS and NAM are too fast. Looking at the ensembles,
the 06Z GEFS mean, while still faster than the 00Z ECMWF, is much
slower than the deterministic 12Z GFS. The ECENS also offers a
slower solution, and is nearly identical to its deterministic run.
So, for this system, a general model blend is favored for day 1/2,
followed by non-GFS, non-NAM blend for day 3.
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Upper Trough Digging Across Great Lakes; Surface Low Developing
Off New England Coast Day 3
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Preference: General model blend through 08.12Z; ECMWF/ECENS/GFS
blend day 3
Confidence: Average (Slightly below average New England Day 3)
19Z update: No major changes for the coastal system on day 3
across New England with the preference toward the ECMWF/ECENS/GFS
mass fields.
---previous discussion---
Shortwave energy moving through southern Canada is expected to
close off as it approaches the Great Lakes region. As the trough
digs over the eastern Great Lakes, a secondary surface low is
forecast to develop offshore the Northeast/New England coast
before rapidly deepening as it moves northeast. Overall this is a
low confidence forecast for day 3 as specific timing is important
for how close the low spawns near the coast and its sensible
weather impacts. For mass fields purposes, the ECMWF and its ECENS
mean has shown the best consistency for the day 2/3 time frame but
the latest 12Z GFS does offer some utility but its surface low is
about ~15 mb weaker than the 00Z ECMWF but with relatively similar
positions. Overall, it's a low confidence forecast but a blend
favoring the ECMWF/ECENS with some GFS (and NAM thermally) would
be appropriate for the Northeast/New England on day 3.
Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml
500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml
Taylor