Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
1217 PM EDT Thu Jul 11 2019

Valid Jul 11/1200 UTC thru Jul 15/0000 UTC

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

12Z Initial Model Evaluation and Preference
Days 1-3, ending 00Z July 15
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...Overall Pattern Across the CONUS...
...Including Tropical Storm Barry...
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Preference: Blend of 00Z ECMWF with 06Z NAM

The dominant weather feature is newly named Tropical Storm Barry
in the Gulf of Mexico. The official center-line forecast track
from the National Hurricane Center is similar in placement and
timing to the 00Z ECMWF and 06Z NAM. This looks like the most
likely scenario from a WPC perspective. The GFS has consistently
been aiming toward the eastern edge of what is possible for a
forecast track. Ensemble clustering reveals a number of GEFS
members that are much farther west, such that the overall
weighting of the multi-ensemble consensus is more inline with the
operational ECMWF forecast. With light steering flow overall, the
track definitely carries some uncertainty, and shifts toward the
east or west may still occur before landfall. Given the model
guidance, however, and the observed ridge / trough positions over
the CONUS, it would appear this storm will drift primarily
northward once it is fully formed. There should be slightly
stronger advective southerly winds on the east side of the system,
compared to the gradient flow on the west side. Tendency to lean
into the latent heat release would also argue for the center to
hang back south and a bit east over time, certainly reflected in
QPF fields from the models in our preference.

In the 12Z cycle, however, the NCEP guidance speaks to the
uncertainty, as the NAM trended farther west, and the GFS also
trended farther west but that just brings it closer to being in
line with consensus.

The models we chose for Barry through Day 3 are also quite similar
in their handling of northern stream features from the Pacific
Northwest to the northern Plains to New England.

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

Burke