Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
225 PM EDT Mon Jul 27 2020
Valid Jul 27/1200 UTC thru Jul 31/0000 UTC
...See NOUS42 KWNO (ADMSDM) for the status of the upper air
ingest...
12Z Model Evaluation Including Preferences and Forecast Confidence
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...Mid-upper level troughing over the Great Lakes and Northeast...
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Preference: General model blend
Confidence: Above average
Models have remained consistent in showing a closed low dropping
southeast across Ontario on Monday and Tuesday before drifting
east across Quebec on Wednesday and Thursday. Meanwhile, a larger
scale trough is shown deepening and moving east across the Great
Lakes into the Northeast -- driving a well-defined surface cold
front through the region. Overall, models are in good agreement
with the larger scale pattern through late Thursday.
...Mid-level energy over California/Great Basin...
...Energy advancing southeast across the Plains by Wednesday...
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Preference: General Model Blend through 72 hours, followed by a
solution more similar to the NAM/ECMWF the central Plains
Confidence: Average
Models continue to the show the mid-level energy that is currently
over California lifting to the northeast into the northern
Intermountain Region and Rockies Monday and Tuesday, before
dropping southeast into the High Plains along the eastern
periphery of an amplifying ridge centered over the Southwest and
Great Basin. Models continue to show some timing differences,
especially late in the period with a well-defined shortwave that
is forecast to settle into the central Plains on Thursday. While
most models have trended faster with this feature, including the
12Z ECMWF, consensus suggests the GFS is too fast dropping this
system south through the central Plains on Thursday.
...Upper low/trough approaching the Pacific Northwest...
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Preference: General model blend through 60 hours, followed by a
lean toward the GFS and ECMWF
Confidence: Average
Models show a deepening upper low settling south from the Gulf of
Alaska into the northeastern Pacific. While the strong downstream
ridge is expected to keep the low center well offshore, models do
show some longitudinal differences late in the period -- with the
GFS, ECMWF and their latest ensemble means slightly farther east
than the NAM and UKMET. The NAM is also on the southern edge of
the envelope guidance with the low center as well.
Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml
500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml
This product will terminate August 15, 2020:
www.weather.gov/media/notification/pdf2/scn20-58pmdhmd_termination.
pdf
Pereira