Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
239 AM EDT Fri Apr 27 2018

Valid Apr 27/0000 UTC thru Apr 30/1200 UTC

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

00Z model evaluation...with final preferences
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

...Evolution of the eastern CONUS trough through Sunday...
...Shortwave pushing through the Southeast today, phasing with
digging wave into the Great Lakes and Northeast by Saturday...
...Weak East Coast surface low development Friday-Saturday...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: non 00Z NAM blend
Confidence: Average

Minor detail differences exist with this system, but the 00Z NAM
ends up toward the slower side with a surface low and related cold
front moving through the central and northern Appalachians
Saturday. Toward the end of the period...12Z/30, the 00Z UKMET/CMC
appear to have adjusted back toward the GFS/ECMWF blend, with
better ensemble support existing for a non 00Z NAM blend.


...Positively tilted shortwave over the southern Plains, digging
toward Florida tonight...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: General model blend
Confidence: Average

The models show similarly with this system.


...Closed low reaching the West Coast today, opening into a trough
over the Northwest by Monday...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: 00Z NAM, 00Z GFS, 00Z ECMWF blend
Confidence: Average

The latest ensemble spaghetti height plots show the 00Z UKMET and
00Z CMC differ from the better clustering represented well in the
ensemble means. While the 00Z GFS and 00Z ECMWF show the best
agreement to the ensemble means, cannot rule out the 00Z NAM as
part of a blend, given detail differences in individual vorticity
maxima as the closed low begins to open up heading into Monday.


...Weak southern stream shortwave ejecting out toward the southern
High Plains by Saturday...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: non 00Z UKMET blend
Confidence: Slightly above average

The 00Z UKMET continues to stand out as stronger regarding
mid-level heights crossing into Texas on Saturday. While it and
the 00Z CMC backed off of their previously strong solutions, only
the 00Z UKMET stands out from the strong ensemble support for a
non 00Z UKMET blend.


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

Otto