Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
111 PM EDT Fri Jun 01 2018

Valid Jun 01/1200 UTC thru Jun 05/0000 UTC

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

12Z model evaluation including the NAM/GFS and preliminary
preferences

Model initialization errors do not appear to be sufficiently large
to impact their forecasts of large scale features.

...Upper trough crossing the Great Lakes/Ohio Valley today and
Mid-Atlantic Sat/possibly off the coast Sun...
...Coastal low off of the northern Mid-Atlantic coast through
Monday morning...

Preliminary Preference: 00Z ECMWF/06Z GEFS mean blend
Confidence: Average

Models show good consensus with the shortwave as it crosses the
Great Lakes/Ohio Valley/Appalachians through Sat morning, and the
NAM/GFS handle the feature similarly to consensus. The upper wave
should prompt a surface low to develop along the Mid-Atlantic
coast on Sat, which is then expected to drift slowly east into Sun
before accelerating away from the coast on Monday. The NAM/GFS
handle the low similarly to the model consensus through Sunday.
Some differences emerge by Monday with the GFS keeping the surface
low closer to the Northeast U.S. coast (similar to the 00Z
CMC/UKMET) and the NAM farther offshore, similar to the 00z ECMWF.
By Monday the 06Z GEFS mean was most closely positioned to the
center of the spread. A blend between the 00Z ECMWF and 06Z GEFS
mean should best represent the consensus at this time.


...Upper trough moving from the Rockies into the northern plains
today/tonight, and upper MS Valley Sat night...

Preliminary Preference: GFS/00Z ECMWF blend
Confidence: Average

The NAM/GFS handle this features similarly to the model/ensemble
consensus through tonight, and by Saturday the NAM (along with the
00Z ECMWF) become slightly faster than consensus while the GFS
(along with the 00Z UKMET) were slower. At this time a GFS/00Z
ECMWF blend should represent a middle ground/consensus solution
for this system.


...Mid-level vorticity maximum entering the Southwest U.S. on
Saturday...

Preference: General model blend
Confidence: Slightly above average

The NAM/GFS handle this feature similarly to the model consensus,
tracking it along the periphery of the broad upper ridge anchored
across the southern tier. The consensus, brings it across the Four
Corners region by Sun and into the central plains, by Mon.


...Upper trough reaching the Pacific Northwest Sunday/Monday...

Preference: General model blend
Confidence: Above average

The models show minor differences with this system, and the 12Z
NAM/GFS are comparable to the consensus. Given the relatively
small spread, a general model blend is preferred to smooth out
these smaller scale differences.


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

Ryan