Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
230 AM EDT Tue Apr 16 2019

Valid Apr 16/0000 UTC thru Apr 19/1200 UTC

...See NOUS42 KWNO (ADMNFD) for the status of the upper air
ingest...

00Z Model Evaluation...with Preferences and Confidence
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...Overall Pattern Across the CONUS...
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Preference: Non-00Z NAM blend
Confidence: Slightly above average

The main focus across the CONUS during this period is the long
wave trough coming ashore over the Pacific Northwest late on Day 1
that evolves into a full latitude trough in the center of the
country by late Day 3. Both the 00Z NAM and 00Z GFS remain close
to the consensus as the long wave trough lengthens over the
Southwest and Southern Plains during Day 2. After that time, both
models become slower than their non-NCEP counterparts as the
trough takes on a full latitude position from the Upper Great
Lakes into the Lower MS Valley.

Both the 00Z NAM/GFS are close to the pack with the surface low
pressure system associated with the evolving trough tracks from
Southeast CO toward the Upper Great Lakes during Day 3. The 00Z
GFS becomes a bit faster than the consensus as this occurs, but
remains within the solution envelope.

There is more model spread concerning the potential for secondary
surface developing at the end of a cold front extending into the
Gulf States late on Day 3. The 00Z NAM (and 00Z UKMET) are
indicating a deeper surface wave over western FL, with the 00Z NAM
deeper than the 00Z UKMET. Because of this, the 00Z NAM excluded
from the preferred blend.

There are some timing differences with the next short wave
approaching the Pacific Northwest late on Day 3. The 00Z GFS is
faster than the consensus, with the 00Z ECMWF on the slower side
of the envelope (though it has been speeding up with this feature
over the past 3 runs). At this point, the sensible weather
differences are fairly small with this feature, so a general model
blend should suffice.


Model trends at www.wpc.noaa.gov/html/model2.html
500 mb forecasts at www.wpc.noaa.gov/h5pref/h5pref.shtml

Hayes