Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
117 PM EDT Fri May 03 2019

Valid May 03/1200 UTC thru May 07/0000 UTC

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

12Z NAM/GFS Evaluation with Preliminary Preferences and Confidence
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...General overview of the CONUS through 00Z/07...
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Preference: Blend of the 00Z UKMET/ECMWF
Confidence: Slightly above average

A longwave trough that covers most of the northern half of the
nation from the Northwest to the Great Lakes will flatten some and
slowly edge east over the next 3 days. Meanwhile, a weak southern
stream perturbation will enter Texas later today and reach the
East Coast for Sunday as a closed low reaches California.

There is broad agreement with the mass fields for many of these
features but there are two differences worth noting. First, the
ensembles show better agreement with the 00Z ECMWF/UKMET with the
shortwave tracking from Texas to the East Coast and the resulting
frontal wave near the Mid-Atlantic region for Sunday. The 00Z CMC
is more amplified as is the case with other features in the
northern stream and is not preferred. The 12Z NAM/GFS meanwhile
show timing differences with the 12Z GFS significantly faster.

The other feature to note is across the Northwest with a shortwave
amplifying toward the northern Rockies by Monday. Here, the 00Z
ECMWF/UKMET show more amplification in the base of the trough
compared to the flatter 12Z NAM/GFS, with the ensemble means more
closely aligning with the ECMWF/UKMET solutions.


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

Otto