Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
246 AM EDT Thu May 31 2018

Valid May 31/0000 UTC thru Jun 03/1200 UTC

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

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

General Preference: Blend of 00Z GFS; 00Z ECMWF; 00Z UKMET
Overall Confidence: Slightly above average

---06Z UPDATE---

No change to the preliminary preference. Models have continued to
trend slower and flatter with the wave moving into the Southwest
than the NAM, and the NAM and CMC still appear the most different
with the Great Lakes trough. Prefer the consistency of the ECMWF,
GFS, and UKMET, and they provide a reasonable blend for the
overall pattern.

---PREVIOUS DISCUSSION---

Models do not appear to have significant initialization errors
that would impact their forecasts. Overall, there is reasonably
good agreement overall, particularly with the synoptic scale
features. This includes the Great Lakes trough gradually shifting
into the Mid Atlantic, the strong trough moving from the Pacific
Northwest to the Great Lakes by Saturday, a southern-stream vort
max and trough pushing into the Southwest, and a ridge over the
Southern Plains.

The largest differences were with the 00Z NAM and 12Z CMC. The NAM
showed a much stronger trough moving from the Plains into the
Great Lakes on Saturday, with a closed low even developing at the
base of the trough over Wisconsin by the end of the short term
period. It also was fastest and strongest with the trough moving
into the Southwest, and given the weak flow pattern that far south
-- model consensus for a slower approach seems more likely. The
CMC showed its largest differences with the Great Lakes trough as
well, with a much flatter wave and a more amplified downstream
ridge.

In general, the UKMET, GFS and ECMWF offer reasonably good
agreement in their mass fields and a blend of the three is very
consistent with ensemble means as well. The overall preference is
for a blend of the three.


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

Lamers