Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
1220 AM EDT Mon Apr 15 2019

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

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

00Z NAM/GFS Evaluation...with Preferences and Confidence
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

...Overall Pattern Across the CONUS...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: General model blend through 17/00Z, then 00Z GFS/12Z
ECMWF blend thereafter
Confidence: Slightly above average

There are two systems of note across the CONUS for this forecast
package. The first system is the negatively tilted long wave
trough and surface low tracking from the Ohio Valley early on Day
1 to Newfoundland by the end of Day 2. The 00Z GFS is a bit faster
with the surface low through 16/00Z, but comes back into agreement
with the consensus thereafter. Both the 00Z NAM and the 12Z ECMWF
indicate a possibly secondary surface low developing over southern
New Hampshire around 16/06Z, but both rejoin the pack with the
surface low after that time. Based on the above, a general model
blend is preferred with above average confidence.

The second system is a developing the long wave trough crossing
the Pacific Northwest before 16/00Z. Both the 00Z NAM and 00Z GFS
showed good agreement with the consensus through Day 2, After that
time, the NAM appears to drop short wave energy into the trough
more quickly that the consensus, slowing the progression of the
long wave trough as it reaches the Central and Southern Plains by
the end of Day 3 (18/12Z). The 00Z GFS is close to the pack with
the long wave trough evolution, but is faster with its surface low
as it tracks from OK into WI by 18/12Z. The 12Z ECMWF has been
more consistent with this feature, and more weight should be given
to the 12Z ECMWF concerning the surface low track by 18/12Z (which
has the support of the 12Z ECMWF ensemble and the 12Z GEFS mean).
Given the spread in the placement of the surface low during Day 3,
confidence is average.


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

Hayes