Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
156 AM EST Sat Feb 09 2019

Valid Feb 09/0000 UTC thru Feb 12/1200 UTC

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

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

...Eastern U.S...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: General model blend through 11.12z; ECMWF/CMC/UKMET
blend after
Confidence: Average

Good model agreement in the near term with the closed low and
surface cold front track/speed across the Great Lakes and
Northeast. Most of the energy with that system will pull north of
the CONUS by Saturday morning. With subtropical ridging anchoring
across southern Florida.

Model differences increase toward the end of the forecast period
as a system developing in the central US moves toward the East
Coast. Earlier biases in the 00z GFS across the central US
continue as the low moves into the lower Great Lakes with a cold
front sweeping across the East Coast.


...Central/Western U.S...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: General model blend...through 11.00z
            ECMWF/CMC/UKMET blend...after 11.00z
Confidence: Average to Slightly Below Average


07z update: With the rest of the 00z guidance now in, the GFS (and
NAM) remain the outliers for the central US cyclone on Day 3.
There is rather good agreement in the operational runs of the
ECMWF/CMC/UKMET with its track from OK Panhandle to the lower OH
Valley.

---previous discussion---

An active weather pattern is expected to develop across the
western U.S. through the forecast period with several impulses
moving onshore. Initially, two mid/upper level features are moving
across the western US, one opening up as it moves onshore across
central California while a stronger closed low drops through B.C.
and into Washington State. Through about 48 hours there is
favorable model agreement and a general model blend can be used.

Much of the energy associated with the Pacific Northwest closed
low will be ejecting downstream across the Plains by late Monday
which will allow surface low pressure to develop in the lee of the
Rockies. Model difference become more substantial by Tuesday as
the shortwave trough takes on a negative tilt. The 00Z GFS is
considerably stronger with this feature and also further northwest
with its surface low track, particularly compared to the ECMWF.
The UKMET is slower/south while the NAM is fast/east. Overall,
model spread is much higher beyond 48 hours as this system ejects
into the central US and the operational GFS appears to be an
outlier this cycle, so the preference will be for a blend of the
ECMWF/CMC and NAM to some degree beyond 48 hours.

Back toward the Pacific Northwest, another in a series of impulses
looks to move into Washington State Sunday night and again Monday
night. There is a fair amount of spread in the operational runs
with respect to the timing and placement of the synoptic features.
The GFS and the NAM appear to be slightly faster compared to the
rest of the models. A blend toward the ECMWF/CMC is preferred for
this portion of the CONUS beyond 48 hours.


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

Taylor