Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
1254 AM EDT Tue Apr 23 2019

Valid Apr 23/0000 UTC thru Apr 26/1200 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: General model compromise
Confidence: Slightly above average

Models were in generally excellent agreement through 25.00Z
(Wednesday evening), with a similar synoptic pattern and limited
model spread. After that, there is a divergence related to
northern stream shortwaves digging into the Great Lakes, the
southern stream trough ejecting out of Texas, and the interaction
of the two. The 12Z ECMWF (and its ensemble) generally shows
stronger shortwaves in the northern stream with lower heights
aloft; this leads to a more ideal phasing, and a negatively tilted
trough and stronger cyclone over the Eastern US. ECMWF models
generally show higher QPF by Day 3 in the Upper Ohio Valley. The
00Z GFS and NAM, by contrast, lag the southern stream trough more,
have weaker northern stream shortwaves, and show less phasing.
This suppresses the heavier QPF to the south. There is no clear
bias to lead to a preference of these extremes one way or another.
The 12Z UKMET and CMC offer somewhat of a compromise in their mass
fields and QPF patterns. The preference is to go with a
broad-based model blend through Wednesday, and then begin to lean
toward a compromise forecast thereafter.


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

Lamers