Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
142 AM EST Thu Jan 31 2019

Valid Jan 31/0000 UTC thru Feb 03/1200 UTC

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

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

...Overall Pattern across the CONUS (except for West Coast)...
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Preference: 00Z GFS/ECMWF/UKMET blend
Confidence: Average

...07Z update...

Timing/amplitude differences remain with the remains of a
mid-level closed low currently west of the California coastline as
the shortwave reaches the Gulf Coast states Saturday into Sunday.
However, there were adjustments made by the 00Z UKMET/CMC in the
direction of the previous GFS/ECMWF blend with a 00Z
GFS/ECMWF/UKMET blend now representing a decent compromise for
this system. Elsewhere east of the Rockies, adjustments in the 00Z
ECMWF/UKMET/CMC were minor compared to their previous 12Z cycles.

...previous discussion follows...

The pattern across the lower 48 will be undergoing change with the
current anomalous upper trough across the Great Lakes and
Northeast departing to the north as ridging begins to build out
East in advance of upper troughing developing across the western
U.S.

Overall, the models show fair agreement`except out West which is
discussed in the section below. A compact closed low currently off
of the coast of California will weaken and move into the southern
Plains Saturday morning and Southeast for Sunday morning. The 00Z
NAM and 12Z CMC are on the edges of the deterministic/ensemble
guidance with the NAM stronger and the CMC faster. The 12Z UKMET
is displaced toward the southern side of the models with the 00Z
GFS/12Z ECMWF fairing close to the better model clustering in the
middle. The 12Z CMC is displaced toward the northern side of the
models with a weak shortwave approaching the northern Mid-Atlantic
states Friday evening. Elsewhere, differences are relatively minor
with a 00Z GFS/12Z ECMWF blend lying close to the middle of the
ensemble clustering.

...West Coast...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: 00Z NAM/ECMWF/UKMET blend
Confidence: Average

...07Z update...

The 00Z UKMET adjusted toward the NAM/ECMWF with the 00Z ECMWF
slightly faster with the base of the trough moving into the
Southwest Sunday morning. The 00Z CMC went south of its previous
cycle regarding the upper trough and surface low offshore. Here, a
00Z ECMWF/NAM/UKMET blend appears reasonable.

...previous discussion follows...

As a large upper trough approaches the West Coast on Friday, a
closed low is expected to form west of northern California as a
northern stream trough crosses the Pacific Northwest. The biggest
differences are with the closed low/trough nearing California with
the 00Z GFS faster than a majority of models. The ensemble trends
over their past 4 cycles has generally been slower, but the slow
12Z UKMET is a near outlier here. The timing of the 00Z NAM and
12Z ECMWF fits well in the middle of the latest ensemble
clustering with the 12Z CMC showing up fast and 12Z UKMET slow.
While confidence is higher than yesterday, there is enough room
for adjustments based on the ensemble data that confidence is
average at this point in time.

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

Otto