Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
1256 AM EDT Sun Sep 15 2019

Valid Sep 15/0000 UTC thru Sep 18/1200 UTC

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

00Z Model Evaluation with Preferences and Forecast Confidence
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...Deep Latitude Trof Entering the West by Monday; Southwest
shortwave...
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Preference: General Model Blend Day 1/2; Non-UKMET blend Day 3
Confidence: Average

Deepening trough over the western U.S. through the period will
eject a shortwave trough into the Rockies and Northern Plains by
Day 3. The latest round of models have come into better agreement
with its depth and orientation as it moves on shore such that a
general model blend can be applied for Day 1/2. For Day 3, a
shortwave will round the trough and lift into the northern Rockies
and Northern Plains. The UKMET continues to be too fast compared
to the rest of the guidance. By the end of Day 3, the system is
expected to deepen somewhat (which all the models do), but the
GFS/NAM are much stronger compared to the ECMWF/CMC. Finally,
another closed low is then expected to drop into the Pacific
Northwest, and here model differences are quite high. The best
agreement at this time seems to be with the ECMWF/GFS/NAM.


...Tropical Storm Humberto...
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Preference: Official NHC Forecast
Best Proxy: General model blend through 24 hours; GFS/NAM blend
after
Confidence: Average

Humberto continues to exhibit signs of strengthening per recent IR
imagery showing convective bursts near the center, though most of
this is displaced to the northern half of the system. Its forward
direction is generally north/northwest at about 5 kt, per the
latest NHC advisory. In the next 24 hours, Humberto is expected on
this general direction before making a turn to the northeast after
36 hours. The latest guidance is tightly clustered through 24
hours, with the GFS/NAM left of the center while the non-NCEP
guidance slightly to the right of the official track. Differences
increase beyond 24-36 hours, with respect to how quickly the
system turns northeast and to what degree. The GFS/NAM suggest a
slower/more gradual turn while the ECMWF is slower but further to
the right. Meanwhile, the UKMET while initially to the right of
the track, then takes a more northerly turn. At 84 hours, the
official point lies near the consensus, but the spread is
considerable between the various deterministic models.


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

Taylor