Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
1252 PM EDT Mon Aug 26 2019

Valid Aug 26/1200 UTC thru Aug 30/0000 UTC

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

12Z Model Evaluation with Preferences and Forecast Confidence
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...Overall Pattern Across the CONUS...
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Preference: Non-NAM blend
Confidence: Slightly above average

Models are in fairly good agreement over the next few days with
their depictions of the mass fields, with most deterministic
models well within the envelope of ensemble spread. The notable
exception seems to be with the 12Z NAM, which has a much stronger
wave rounding the base of the Great Lakes trough on Wednesday,
leading to a surface low much closer to the Northeast coast on
Thursday. This yields heavier QPF across much of New England.
Given the lack of ensemble support, the preference is for a
non-NAM blend overall, based on the mass fields. This may affect
the NBM QPF over the region.

Otherwise, there are considerable QPF differences on Day 2 and Day
3 over the Southern Plains, with global models concentrating
rainfall near the Red River from Tuesday Night into Wednesday,
while hi-res models are considerably further southwest. The
preference here will be to strike a balance, as convective
rainfall often ends up slightly further south than global models
would indicate. However, hi-res models are not exactly consistent
enough to pinpoint a location and could be too far south given the
robust signal in global models. These differences may likewise
affect NBM QPF given the inclusion of the NAM Nest in the Day 2-3
time frame.


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

Lamers