Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
1254 AM EDT Sat Jul 13 2019

Valid Jul 13/0000 UTC thru Jul 16/1200 UTC

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

00Z Model Evaluation Including Preference and Forecast Confidence
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

...Overall Pattern Across the CONUS...
...Tropical Storm Barry...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: 00Z GFS/12Z ECMWF/12Z CMC blend (CONUS)
            00Z GFS...through 36 hours (T.S. Barry)
            12Z ECMWF...after 36 hours (T.S. Barry)
Confidence: Average

The dominant weather feature impacting the CONUS through the
short-range period will again be Tropical Storm Barry which is
currently offshore of the central Louisiana coastline. The 03Z NHC
forecast track of Barry is closest to the 00Z GFS now through
about 36 hours, and thereafter follows more closely to the 12Z
ECMWF. The 00Z GFS did trend a bit farther west overall through
the 84 hours. The 12Z UKMET and 00Z NAM remain westward tracking
outliers relative to the GFS/ECMWF/NHC tracks. The 12Z CMC for its
part is a bit east of the GFS/ECMWF/NHC cluster but in time
becomes a bit of a slower outlier.
 
Regarding the 00Z hires model guidance and their handling of
Barry, the 00Z NAM-conest is the closest to the NHC track, but
does edge left of the NHC track after 24 hours. The 00Z NMMB
solution is well left of the NHC track through 48 hours as it
tracks Barry into southeast TX. The 00Z ARW/ARW2 solutions are
slower than the NMMB, but are also both left of the NAM-conest and
the NHC track in general. The 00Z HRRR is closest to the ARW2
solution. Therefore, it can be concluded that all of the hires
models track left of the NHC track, and especially after 24 hours.
Please consult the latest NHC forecast advisory for more details
on Barry.
 
Elsewhere across the country, there will be a shortwave trough
moving into the Northwest through the period as multiple smaller
scale vorts/impulses traverse the northern tier of the nation
around the northern flank of a fairly strong subtropical ridge
over the Four Corners region and stretching east across portions
of the central Plains and Midwest. This ridge is expected to break
down by Monday and Tuesday as the upstream trough advances deeper
into the western U.S. The 00Z NAM is a tad stronger than the
global models with this trough, with the 12Z UKMET generally on
the weaker side of the model envelope. There are some modest
timing differences as well with the 12Z non-NCEP guidance
collectively a bit slower than the NAM/GFS solutions. However, by
the end of the period, the NAM is the most out of phase with the
remaining guidance, and especially across the northern Rockies and
northern Plains.

Over the Northeast, there will be a shortwave trough advancing
through this weekend and then lifting through southeast Canada
through early next week. Model spread with this troughing is
rather modest, but gradually the non-NCEP solutions slow the
trough a little bit versus the 00Z GFS as the trough begins to
advance offshore and up across the Canadian maritimes.

The preference for the CONUS outside of Tropical Storm Barry will
be for a blend of the 00Z GFS, 12Z ECMWF and 12Z CMC. The T.S.
Barry NHC track is closest to the GFS through 36 hours, and then
follows the ECMWF thereafter. However, it should be noted that all
of the 00Z hires guidance take Barry left of the NHC track in time
and there is at least one global model (the UKMET) that supports
that idea as well.


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

Orrison