Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
256 PM EDT Wed Jul 10 2019

Valid Jul 10/1200 UTC thru Jul 14/0000 UTC

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

12Z Model Evaluation Including Preference and Forecast Confidence
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...Overall Pattern Across the CONUS...
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Preference: General model blend (across the CONUS)
            See latest NHC advisories for P.T.C. TWO (Gulf Coast)
Confidence: Slightly above average

Over the next 3 days, there continues to be reasonably good
agreement with the synoptic pattern across the CONUS. Shortwave
energy will track across the Great Lakes and into the Northeast
U.S. while a ridge builds and retrogrades to the Four Corners
region. Tropical development is expected across the northern Gulf
of Mexico, and the NHC has initiated advisories on Potential
Tropical Cyclone Two (P.T.C. TWO). The track of this system will
be dictated by the strength/position of the strengthening ridge to
the north and west of the cyclone. Elsewhere, there will be a new
shortwave trough impacting areas of the Pacific Northwest, but the
bulk of the height falls are expected to remain offshore.

For the northern tier of the U.S., a general model blend can be
applied where the guidance is well clustered with timing and depth
of the shortwave trough evolution. Likewise, a general model blend
can be applied for the troughiness offshore the Northwest that
brushes the Pacific Northwest through the period give reasonably
good model clustering and with the intent of resolving some of the
smaller scale mass field differences.

The biggest model differences lie with the P.T.C. over the
northern Gulf of Mexico which is forecast to move west-southwest
and then eventually west and northwest through Saturday while
approaching areas of southern LA and the upper TX coast. The 12Z
NAM has the fastest and farthest west track of the storm, and
suggests a direct impact on the middle TX coast by early Saturday.
The 12Z UKMET is the strongest solution and is also farther west,
although not as fast as the NAM, and supports a direct impact
midday Saturday along the upper TX coast. The UKMET definitely has
a much stronger subtropical ridge building north of the system
through the period which is aiding its farther west track,
however, the UKMET is also trending farther west with the storm.

On the flip side, the 12Z GFS is the slowest solution and supports
a recurvature up across south-central to southeast LA by early
Saturday. This then leaves the 12Z ECMWF and 12Z CMC which are
clustered in between the faster and slower camps. Although, the
ECMWF did trend a tad right of its previous track. Meanwhile, the
CMC trended a tad farther west. A blend of the ECMWF/CMC camp is
closest to the 15Z NHC forecast track at this time, and supports a
direct impact across southwest to south-central LA by midday
Saturday. Please consult the latest NHC forecast
advisories/discussions for more details on P.T.C. TWO.


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

Orrison