Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
242 AM EDT Mon Apr 29 2019

Valid Apr 29/0000 UTC thru May 02/1200 UTC

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

00Z Model Evaluation w/Preferences & Confidence Intervals
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NAM/GFS initialization issues appear small and do not seem to
degrade their short range forecasts.


Pattern Across the Lower 48
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Preference: Non-NAM blend
Confidence: Above average

Overall see pretty good agreement amongst the guidance on the
synoptic scale over the next three days.  Components of the 00z
NAM stand out as outliers and less likely outcomes. The NAM ends
up stronger with embedded shortwave energy within the
Intermountain West on Tuesday, which ends up resulting in it also
being stronger with energy across the northern Plains on
Wednesday. These differences with the embedded shortwave energy
result in a slightly different evolution of the larger scale
trough and sensible weather impacts across the Rockies/Plains by
later Tuesday through Wednesday night. The NAM is on its own and
trends seem to be against it as well. It is different enough to be
removed form our preferences at this time.

While there are some differences amongst the 00z ECMWF, 00z
Canadian, 00z GFS, and 00z UKMET, they are generally minor and a
look at the past several runs of each shows a convergence of
solutions. From a large scale standpoint, a blend of these models
should suffice at this time...with most of the spread amongst
these solutions the result of less predictable convectively-driven
factors.


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

Roth/Chenard