Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
234 AM EDT Tue May 15 2018

Valid May 15/0000 UTC thru May 18/1200 UTC

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

00Z model preferences and confidence intervals
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
GFS/NAM initialization errors do not seem to degrade their short
range forecasts.


West/Plains
~~~~~~~~~~~
Preference: Model blend; confidence above average

The guidance shows good agreement concerning the evolution of the
digging trough and the weakening system moving into Montana, so a
blend of the 00z NAM, 00z GFS, 00z ECMWF, 00z Canadian, and 00z
UKMET should work out well in the mid-level height and surface
pressure pattern, which is preferred with above average confidence.


Southeast/OH Valley/Mid-Atlantic States
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: Non-NAM blend; confidence above average

The 00z NAM uses convective/gridscale feedback over the Mid-South
and Ohio Valley to overly deepen a mid-level system in the OH
Valley which is much stronger than the other deterministic and
ensemble guidance.  This leads to a quicker recurvature to the
Gulf system into the Southeast and Mid-South and a frontal
placement in the Mid-Atlantic States which is too far north.  The
00z NAM was not considered reasonable from Wednesday morning
onward.

Otherwise, the deterministic guidance lies within the ensemble
envelope regarding the depth of the Gulf of Mexico upper trough
and the movement of the low into the Southeast and a
boundary/front to its west and north.  A compromise of the 00z
ECMWF, 00z UKMET, 00z Canadian, and 00z GFS is preferred with
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