[meg.infolist.announce] Upgrade to the GFS to V15.1

[Brian Gross - NOAA Federal]

Dear GFS Community,

As we have discussed on the MAP and other fora, NWS heard concerns from the
weather community about our planned implementation of the GFS model upgrade
from version 14 to version 15, due to cold and snow biases observed in the
model.

In February, we paused our implementation timeline to review these concerns
and the data, and explore potential improvements we could make. During this
time, we made three modifications to the model (now called version 15.1) to
alleviate excessive snow and cold bias in the model and address feedback
from the community. The results show an improvement over biases previously
found in the model. As a result of the overall advantages offered by GFS
version 15.1 we are confident moving forward with the upgrade.

Yesterday, we announced via a public information statement
<https://www.weather.gov/media/notification/pns19-09gfs_v15_1.pdf> that the
National Weather Service is lifting the pause on the implementation the
U.S. Global Forecast System (GFS) with the Finite-Volume Cubed-Sphere (FV3)
dynamical core - version 15.1 of the model. We will conduct a planned
30-day technical test and upon successful completion of the test, version
15.1 will be the new operational model. Additional details about the 30-day
technical test went out today via an official service change notice
<https://www.weather.gov/media/notification/scn19-40gfs_v15_1.pdf>.

When version 15.1 becomes operational after the end of the final technical
test, we will continue to run version 14 in parallel through September 2019.

Additional material relevant to the performance of the new model
configuration is available here
<https://docs.google.com/presentation/d/1EafmMwFpg7V8yZwqQ0WT7WIxzGRKSvBOMbLc7hAukck/edit?usp=sharing>.

As was demonstrated on the path to upgrading GFS, it is important for EMC's
model development efforts to receive feedback from the community of
stakeholders. We are counting on continued feedback as we commence with
future model upgrades. Thank you for your help in advance!

Cheers,

Brian D. Gross
Director, NOAA/NWS/NCEP/Environmental Modeling Center

5830 University Research Court, Room 2050
College Park, MD 20740

Email: Brian.Gross at noaa.gov
Phone: 301-683-3748
Cell:  609-439-9702
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