Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
1141 PM EST Sun Jan 06 2019

Valid Jan 07/0000 UTC thru Jan 10/1200 UTC

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

00Z Model Evaluation...with Preferences and Confidence
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

...Overall Pattern Across the CONUS...
Preference: Non-NAM blend for eastern US; general model blend
elsewhere across CONUS
Confidence: Slightly above average

Shortwave troughs tracking across the Rockies currently will eject
out into the central Plains and eventually carve out a deeper
longwave trough over the Great Lakes and Northeast US by
Wednesday. A surface low is expected to develop in response to the
deepening mid/upper level trough over New York then turn northeast
through Nova Scotia by the end of the forecast period. Meanwhile
ridging aloft and high pressure at the surface will provide more
benign weather for the middle of the CONUS. Finally, a couple of
weather systems will keep bringing precipitation to the western
US.

One area of model differences lies across the Northeast US with
the developing surface low and its track off the coast into Nova
Scotia. The 00z NAM is too fast and inland compared to the rest of
the model spread, and overall its upper trough is considerably
stronger/deeper compared to any of the other deterministic models.

Other model differences to note are across the western US by the
end of the forecast period (10.12z) as a weak shortwave trough
moves into California. The UKMET is more pronounced with this
feature while the rest of the guidance is flatter/weaker. The CMC
barely has a reflection of it at all.

Overall, a non-NAM blend is still preferred, particularly across
the eastern US with the differences noted about the mid/upper
trough and surface low track/speed. Outside of that, a general
model blend would likely suffice for the remainder of the CONUS.


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

Taylor