Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
113 PM EDT Tue Jul 09 2019

Valid Jul 09/1200 UTC thru Jul 13/0000 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: Non-UKMET blend (Northern Plains to the Northeast)
            12Z GFS/00Z UKMET/00Z ECMWF blend (Gulf Coast States)
            Blend of the 12Z GFS and 00Z CMC (Pacific Northwest)
Confidence: Slightly above average

For the majority of the CONUS, there continues to be reasonably
good agreement on the details of the synoptic pattern which will
include a robust upper trough/closed low feature over the northern
Plains advancing east-southeast through the Great Lakes and
Northeast through the end of the week. Also, there will be a
modestly negative height anomaly brushing the Pacific Northwest
and then reloading offshore the Northwest by the end of the
period. Meanwhile, a strong deep layer ridge builds across the
central U.S. which will advance west well across the Four Corners
region and stretch as far east as the middle MS Valley. The
strength and position of this ridge will be important in dictating
the ultimate track of any tropical cyclone development across the
northern Gulf of Mexico over the next several days.

Regarding the initial northern stream trough/closed low over the
northern Plains, the 00Z UKMET is slower and more amplified versus
the remaining guidance. Overall, the 12Z GFS is the most
progressive, with the 12Z NAM/00Z CMC and 00Z ECMWF all just a
little slower. The 06Z GEFS mean and 00Z ECENS mean favor a
solution that overall is a tad more progressive than the model
consensus. A non-UKMET blend should work for this system.

The other region of focus will certainly be the northern Gulf
Coast region as the models have all come into very good agreement
on taking a broad area of low pressure over the FL Panhandle down
to the southwest over the northern Gulf of Mexico where tropical
cyclone development is likely to occur. The 12Z NAM is the most
progressive and weakest solution and supports a direct impact
along the middle southeast TX coast by early Friday. Meanwhile,
the global models are all slower and deeper, with the 12Z GFS, 00Z
ECMWF and 00Z UKMET the deepest solutions overall. However, the
UKMET tracks the system a bit north of the GFS/ECMWF solutions and
would a direct impact across south-central to southeast LA during
the day on Friday and Friday night. The impacts from the GFS/ECMWF
and CMC solutions would be lesser in nature through this time
frame since they still have their low center farther offshore. The
06Z GEFS mean supported a solution slower and weaker than the 12Z
GFS as the latest GFS did trend slower and stronger. Meanwhile,
the 00Z ECENS mean is closely supportive of the deterministic
ECMWF. For now, a consensus of the GFS/UKMET and ECMWF will be
preferred for the time being.

Otherwise, the guidance does support a reloading upper trough
offshore the Pacific Northwest by the end of the period. The 12Z
NAM is the slowest and deepest with this solution, with the 00Z
UKMET the fastest and a tad weaker. The 00Z ECMWF is a bit weaker
as well, but is slower than the UKMET. The 12Z GFS and 00Z CMC
solutions are deeper but split the difference between the
weaker/faster UKMET and the slower/deeper outlier per the NAM.
Based on this, a blend of the GFS and CMC will be preferred for
the energy offshore the Pacific Northwest toward the end of the
period.


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

Orrison