Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
1254 PM EDT Tue Apr 30 2019

Valid Apr 30/1200 UTC thru May 04/0000 UTC

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

12Z Model Evaluation with Preferences and Confidence
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

...Overall Pattern Across the CONUS...
Preference: Non-CMC blend; greater weight to GFS, ECMWF
Confidence: Slightly above average

Models show a reasonable degree of similarity with their mass
fields over the next several days. The greatest differences are
generally confined to the southern stream due to a couple factors:
(1) variation in the amplitude of a southern stream wave arriving
in Texas Thursday Night and Friday, and (2) small variation in
frontal placement and instability.

The 12Z NAM, 12Z GFS and 00Z UKMET show a more amplified southern
stream trough, and thus show more focused precipitation in Texas
on Day 3, while the 00Z ECMWF and 00Z CMC are less amplified and
drier. The ECMWF is not as flat with the flow as the CMC, and thus
offers a reasonable scenario to be blended with the wetter GFS as
a compromise. The ECMWF also shows a more southward placement of a
QPF maxima in the southern Plains on Day 2 relative to the GFS
(and the ensembles follow suit), and a blend should also capture
some of this placement uncertainty.

The CMC seems far too deamplified with the southern stream
pattern, and thus the forecast blend recommendation does not
include the CMC. These pattern differences do lead to substantial
variation in the QPF distribution.


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

Lamers