Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
149 PM EDT Thu Sep 05 2019

Valid Sep 05/1200 UTC thru Sep 09/0000 UTC

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

12Z Model Evaluation, Confidence, and Preferences
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...Overall Pattern Across the CONUS...
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Preference: GFS/ECMWF/CMC blend
Confidence: Average through 60 hours, below average for day 3

Through about 48-60 hours, the general synoptic pattern across the
CONUS will feature strong ridging across the southwest US and
southern Plains while a shortwave trough approaching the Northeast
U.S. interacts with Dorian to be the final kicker as it quickly
lifts offshore the eastern U.S. and into the Canadian Maritimes.
For this period, model guidance show average to above average run
to run and model to model consistency such that a general blend of
the available guidance should suffice across the CONUS. There are
some subtle strength/timing differences noted with the approach of
the Great Lakes and Northeast U.S. shortwave, particularly the
secondary shortwave that moves through on Saturday. The GFS/NAM
are a bit faster while the ECMWF/CMC are a touch deeper.

Beyond 60 hours and further west, the main challenges will be a
couple of shortwaves and a deeper trough approaching the western
U.S. coast on Saturday night into Sunday. The big picture is in
good agreement with all the guidance showing a trough, but the
typical biases in the models are present. The GFS is faster than
most of the guidance while the UKMET is deeper (more south) and
slower, closing off a low across southern California on Sunday
afternoon.

Given the run to run variability, the preference would be to lean
toward the previous preference somewhat and go with a GFS/ECMWF
blend. The CMC can also be incorporated but perhaps to a lesser
weight.


...Hurricane Dorian...
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Please refer to the official National Hurricane Center forecast
track. With the latest (15Z) NHC Advisory, there is good agreement
with the latest model suite through 48 hours as Dorian takes a
northeast turn and begins extratropical transition, interacting
with an approaching shortwave trough from the Great Lakes region.
Beyond 48 hours, there are some differences in the track, with the
UKMET left of the current advisory track and the latest GFS just a
tad east. A general model blend, with a focus on the
GEFS/ECMWF/UKMET will suffice.


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

Taylor