Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
1214 AM EST Fri Mar 08 2019
Valid Mar 08/0000 UTC thru Mar 11/1200 UTC
...See NOUS42 KWNO (ADMNFD) for the status of the upper air
ingest...
00Z NAM/GFS Evaluation Including Preliminary Preference and
Confidence
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...Departing shortwave over the eastern U.S. today...
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Preference: General model compromise
Confidence: Above average
Only minor depth differences with the 700-500 mb shortwave exist
with the 00Z NAM deepest and 12Z CMC flattest. Given the
differences are small, a general model compromise is preferred.
...Shortwave in southern Alberta/Saskatchewan this morning,
tracking east and merging with another shortwave from the north
over Saskatchewan/Manitoba on Saturday...
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Preference: non 12Z CMC blend
Confidence: Average
Some minor timing differences remain with the lead shortwave
moving into Manitoba Saturday morning, but the 12Z CMC was noted
to be slowest and results in a more amplified/closed low solution
for Sunday afternoon over south-central Canada. the 12Z CMC shows
toward the deeper/slower side of the available ensemble spaghetti
height members early Sunday. Greater support is in place for a
broad non-12Z CMC blend.
...Surface low tracking across the Upper Midwest/Great Lakes this
weekend...
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Preference: 00Z NAM, 00Z GFS, 12Z ECMWF blend
Confidence: Slightly above average
There has been convergence with this system compared to yesterday
with the 500 mb shortwave and surface low track across the central
U.S. into the Great Lakes. The 00Z NAM/GFS are slightly quicker
with the upper trough axis and a bit east with the surface low
position by 12Z/10 compared to the 12Z ECMWF/UKMET/CMC. While the
12Z ECMWF is more in line with the ensemble means, given gradual
trends in the spaghetti height plots over the past 3 cycles to be
faster, blending the 12Z ECMWF with the 00Z NAM/GFS seems best at
this time. The 12Z CMC differs enough from the consensus due to
differences with an upstream wave over Canada to bring the 12Z CMC
solution out of line with the remaining consensus, contrary to
trends.
...Closed low over Washington this morning, interacting with the
next Pacific trough/surface low nearing California on Saturday,
developing into a large closed low over or just offshore of
California Monday morning...
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Preference: 00Z NAM, 00z GFS, 12Z ECMWF blend
Confidence: Average
Several pieces of energy coming out of the eastern Pacific will
eventually carve out a deeper trough over the west coast late in
the weekend, while interacting with a retrograding closed low over
the Pacific Northwest. There is fairly good agreement with a
surface low tracking south off of the West Coast and the eventual
large closed low that develops near the California coast, but the
12Z UKMET is displaced farther inland compared to the remaining
consensus at 500 mb. This is reflected in the ensemble spaghetti
heights as well with a better consensus for a 00Z NAM, 00Z GFS and
12Z ECMWF blend with the 12Z CMC a secondary option.
Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml
500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml
Otto