Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
1216 AM EDT Mon Apr 09 2018

Valid Apr 09/0000 UTC thru Apr 12/1200 UTC

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

00Z NAM/GFS evaluation with preliminary model preferences
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
NAM/GFS initialization errors do not seem to degrade their short
range forecasts.


Trough moving into the West late Wednesday
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: Non-UKMET compromise; confidence slightly above ave

The 12Z UKMET is a touch slower than the other guidance aloft.  As
the 12z ECMWF/18z GEFS means show a quicker solution and the
overall trough is broad and the ensemble means are not in perfect
agreement, will lean toward the slightly more progressive 12z
Canadian/12z ECMWF/00z GFS/00z NAM consensus at this time with
slightly above average confidence.


Front moving into the West on Tuesday
Shortwave moving across Great Lakes/Northeast Monday
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
As the guidance is in good agreement with these features, a
compromise of the 12z Canadian/12z ECMWF/12z UKMET/00z GFS/00z NAM
is preferred with above average confidence.


Shortwave/Low moving across the Great Lakes Tuesday
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: Non-NAM blend; confidence slightly above ave

The 00z NAM uses a deeper but broader/less sharp mid-level feature
to yank its surface low track more northerly of the other
deterministic guidance and on the northern periphery of the 12z
global ensemble guidance.  Prefer a compromise of the   12z UKMET,
12z ECMWF, 12z Canadian, and 00z GFS is preferred with slightly
above average confidence.


Trough moving across the East Tuesday/Wednesday
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: Non-NAM blend; confidence slightly above ave

Although the guidance is agreeable in the surface pressure
pattern, the 00z NAM becomes a slow/strong outlier with the base
of the trough moving from the southern Plains through the
Southeast/Florida -- its usual bias -- which leads to a notable
difference in its QPF across Florida.  The general flow pattern
features a long wavelength which argues against an upper trough as
sharp as the NAM.  The ensemble mean solutions show some slight
difference aloft with this feature, but outpace the NAM.  A
compromise of the 12z UKMET, 12z ECMWF, 12z Canadian, and 00z GFS
is preferred with slightly above average confidence.


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

Roth