Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
1213 AM EDT Sat Aug 03 2019

Valid Aug 03/0000 UTC thru Aug 06/1200 UTC

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

00Z Model Evaluation with Preliminary Preferences and Confidence
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...Overall Pattern Across the CONUS...
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Preference: General model blend, less weight on 00Z NAM on Day 3
Confidence: Slightly above average

Models are in fairly good agreement across the CONUS over the next
few days. The synoptic pattern remains relatively consistent, with
a persistent ridge in the Western U.S. and a trough over the East
that gets reinforced by some digging waves.

The primary differences are related to the trough amplitude in the
Southeast and Gulf of Mexico by Day 3 (Monday and Monday Night).
The 00Z GFS, NAM and 18Z GEFS show a more amplified trough, while
the 12Z UKMET, ECMWF and CMC show a less amplified trough. Despite
better ensemble support for the ECMWF and CMC, a strong ridge over
the West can correspond to some downstream trough amplification so
the GFS and NAM cannot be ruled out. The GFS and NAM are generally
wetter than the ECMWF -- this may be partially due to the
differences with the trough and partially due to the usual dry
bias of the ECMWF. Slightly less weight was placed on the ECMWF
QPF over the Southeast on Day 3.

One other difference of note is that the 00Z NAM is producing a
very focused maximum of QPF over the Upper Midwest on Day 3, with
generally very light QPF along the remainder of the front. The GFS
and ECMWF show a stronger QPF signal along the length of the
front, which is generally favored. Therefore, the overall
preference is for a general model blend with less weight on the
NAM on Day 3.


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

Lamers