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000
NOUS41 KWBC 262200 AAC
PNSWSH

Service Change Notice 23-124 Updated
National Weather Service Headquarters Silver Spring MD
500 PM EST Mon Feb 26 2024

To: Subscribers:
 -NOAA Weather Wire Service
 -Emergency Managers Weather Information Network
 -NOAAPORT
 -Other NWS Partners and Employees

From: Ben Kyger
 Director, NCEP Central Operations

Subject: Updated: Upgrade of the Surge and Tide Operational
 Forecast System (STOFS), Effective March 27, 2024

Updated to reflect the new implementation date of March 27, 2024 and
to
update version number to v2.1.7.

On or about March 27, 2024, beginning with the 1200
Coordinated Universal Time (UTC) cycle, the National Centers for
Environmental Prediction (NCEP) will be upgrading the Surge and Tide
Operational Forecast System (STOFS) to v2.1.7.

STOFS v2.1.7 represents a major upgrade of the STOFS modeling system.
It
was last upgraded in January 2023. STOFS v2.1.7 contains several
enhancements improving model performance, resolution, and coverage.
It
includes upgrades to the global modeling system (STOFS-2D-Global) and
to
the 3D component for the Atlantic basin (STOFS-3D-Atlantic).


Model upgrades for STOFS-2D-Global (ADCIRC-based) include:

    -Inclusion of bias correction at station locations where
NOS/CO-OPS
observations are available. This bias correction a) computes the bias
at
these stations by subtracting the combined (storm surge + tide) water
level forecast guidance from the observed water level, b) removes
this
hourly bias from the current cycle’s 6-hour nowcast, c) averages
the bias
over 5 days using the most recent 5 days of nowcasts and
observations, and
d) removes this average bias from the future forecast guidance (with
a 12-
hour linear interpolation from current bias to average bias). This
post-
processing bias correction is implemented in STOFS-2D-Global in the
same
way that Extra-Tropical Storm Surge (ETSS) implements it (also called
“anomaly”, which is the same as the negative bias). Note that no
gridded
bias correction is implemented in this version of STOFS-2D-Global.

    -Improved temporal resolution for GFS forcing, by including
hourly
GFS forcing out to 5 days in the forecast, then 3-hourly from 5 days
to
7.5 days in the forecast. Previously, 3-hourly GFS forcing was used
for
the entire forecast period.

    -Improvements to coastal topography, bathymetry, friction
values, and
the mesh, for improved accuracy of water level forecast guidance.
Specifically, there are improvements to the bottom boundary
conditions
(friction, topography, and bathymetry), and a few mesh nodes were
adjusted
for improvement in performance. Also, a model output station was
added at
a relatively new tide gauge at NOS/CO-OPS Bremerton, WA (9445958).


Model upgrades for STOFS-3D-Atlantic (SCHISM-based) include:

    - Major improvements to the mesh in the watersheds, including
better
resolving of river channels to enhance watershed flow and
connectivity and
to minimize ponding. The mesh in coastal areas such as the Great
South Bay
and Shinnecock Bay is also improved for enhanced accuracy of water
level
forecast guidance.

    - Incorporation of satellite altimetry observations,
specifically
absolute dynamic topography (ADT), to improve open ocean boundary
conditions and overall accuracy. Also, xGEOID20b is used instead of
NAVD88
to improve model initialization and vertical datum referencing.
Station
output will remain in NAVD88, while gridded output (e.g. *field*.nc
and
*.grib2) will be referenced to xGEOID20b.

    - Extending the forecast horizon from 48 to 96 hours into the
future.

    - Expanding the model coverage east and north to include the St.
Lawrence River and improve boundary conditions and overall accuracy,
especially in the Gulf of Maine.


New and existing data files for STOFS-2D-Global and STOFS-3D-Atlantic
will
remain at their current location on the NOAA Operational Model
Archive and
Distribution Service (NOMADS)/FTPPRD web services at:

ftp://ftp.ncep.noaa.gov/pub/data/nccf/com/stofs/prod/
https://www.ftp.ncep.noaa.gov/data/nccf/com/stofs/prod
https://nomads.ncep.noaa.gov/pub/data/nccf/com/stofs/prod/


Below are the changes to the files on NOMADS and FTPPRD web services:

A. File additions and file name changes:

- Additional forecast hours for STOFS-3D-Atlantic CONUS East and
Puerto
Rico (this data will also be made available via the existing NOMADS
Grib
Filter and OPeNDAP applications):

stofs_3d_atl.tCCz.conus.east.f{hour}.grib2
stofs_3d_atl.tCCz.puertori.f{hour}.grib2

Where {hour} = {49,50,51,...,96}, and tCCz is forecast cycle: CC = 12

- The following STOFS-3D-Atlantic files experience file name changes,
increased temporal resolution, and/or an extended forecast horizon
that
results in additional files:

stofs_3d_atl.tCCz.f001_024.field2d.nc and
stofs_3d_atl.tCCz.f025_048.field2d.nc become:
stofs_3d_atl.tCCz.field2d_fhhh1_hhh2.nc

Where {fhhh1_hhh2} =
{f001_012,f013_024,f025_036,f037_048,f049_060,f061_072,f073_084,f085_
096},
and tCCz is forecast cycle: CC = 12

stofs_3d_atl.tCCz.n001_024.field2d.nc becomes:
stofs_3d_atl.tCCz.field2d_nhhh1_hhh2.nc

Where {nhhh1_hhh2} = {n001_012,n013_024}, and tCCz is forecast cycle:
CC =
12

stofs_3d_atl.tCCz.fields.out2d_forecast_day1.nc and
stofs_3d_atl.tCCz.fields.out2d_forecast_day2.nc become:
stofs_3d_atl.tCCz.fields.out2d_fhhh1_hhh2.nc

Where {fhhh1_hhh2} =
{f001_012,f013_024,f025_036,f037_048,f049_060,f061_072,f073_084,f085_
096},
and tCCz is forecast cycle: CC = 12

stofs_3d_atl.tCCz.fields.out2d_nowcast.nc becomes:
stofs_3d_atl.tCCz.fields.out2d_nhhh1_hhh2.nc

Where {nhhh1_hhh2} = {n001_012,n013_024}, and tCCz is forecast cycle:
CC =
12

B. Timeliness changes:

- For the STOFS-2D-Global model, the GRIB2 and SHEF products will be
delivered up to 20 minutes later. The NetCDF products will be
delivered up
to 30 minutes later, while the htp NetCDF files will be delivered up
to 15
minutes earlier.

- For the STOFS-3D-Atlantic model, the SHEF and NetCDF products will
be
delivered up to 45 minutes later, and the GRIB2 products will be
delivered
up to 70 minutes later.


C. File size changes:

- The expanded domain east and north and some SCHISM code I/O changes
increase the following STOFS-3D-Atlantic file sizes:

stofs_3d_atl.tCCz.fields.cwl.maxele.nc
stofs_3d_atl.tCCz.conus.east.cwl.grib2
stofs_3d_atl.tCCz.puertori.cwl.grib2

Where tCCz is forecast cycle: CC = 12

- The reduction in the station number from 342 to 108 or 107
decreases the
following file sizes:

stofs_3d_atl.tCCz.fcast.station.profile.nc
stofs_3d_atl.tCCz.ncast.station.profile.nc
stofs_3d_atl.tCCz.points.cwl.temp.salt.vel.nc
stofs_3d_atl.tCCz.points.cwl.nc
stofs_3d_atl.tCCz.points.cwl.shef

Where tCCz is forecast cycle: CC = 12


D. File content changes:

- The Bremerton, WA station is added to the following STOFS-2D-Global
files:

stofs_2d_glo.tCCz.points.cwl.nc
stofs_2d_glo.tCCz.points.htp.nc
stofs_2d_glo.tCCz.points.swl.nc

Where tCCz is forecast cycle: CC = 00, 06, 12, and 18

- Dimension parameters (such as node, nele, nbou, nvel, and
max_nvell) are
changing in the following STOFS-2D-Global files due to the ADCIRC
model
grid change and the adjustment of a few mesh nodes:

stofs_2d_glo.tCCz.fields.cwl.nc
stofs_2d_glo.tCCz.fields.htp.nc
stofs_2d_glo.tCCz.fields.swl.nc

Where tCCz is forecast cycle: CC = 00, 06, 12, and 18

- A new processID "21", which is Extra-tropical Storm Surge Atlantic
Domain (3D), is used for the following STOFS-3D-Atlantic GRIB2 files:

stofs_3d_atl.tCCz.conus.east.f{hour}.grib2
stofs_3d_atl.tCCz.puertori.f{hour}.grib2
stofs_3d_atl.tCCz.conus.east.cwl.grib2
stofs_3d_atl.tCCz.puertori.cwl.grib2

Where {hour} = {1,2,3,...,96}, and tCCz is forecast cycle: CC = 12

- Due to the change of the vertical datum referencing to xGEOID20b
for the
STOFS-3D-Atlantic model, the number of stations is reduced from 342
to 108
or 107 (i.e. xGEOID20b to NAVD88 or MLLW conversion is not available
for
some stations). The affected files are:

stofs_3d_atl.tCCz.fcast.station.profile.nc
stofs_3d_atl.tCCz.ncast.station.profile.nc
stofs_3d_atl.tCCz.points.cwl.temp.salt.vel.nc
stofs_3d_atl.tCCz.points.cwl.nc
stofs_3d_atl.tCCz.points.cwl.shef

Where tCCz is forecast cycle: CC = 12

- The following files have new variables:

Variable crs is added to provide the Coordinate Reference System
(CRS)
definition in the following file:

stofs_3d_atl.tCCz.fields.cwl.maxele.nc

Where tCCz is forecast cycle: CC = 12

Variables crs, SCHISM_hgrid_face_x, SCHISM_hgrid_face_y,
SCHISM_hgrid_edge_x, SCHISM_hgrid_edge_y, evaporationRate,
precipitationRate, windStressX, and windStressY are added in the
following
files:

stofs_3d_atl.tCCz.fields.out2d_nhhh1_hhh2.nc
stofs_3d_atl.tCCz.fields.out2d_fhhh1_hhh2.nc

Where {nhhh1_hhh2}={n001_012,n013_024},
{fhhh1_hhh2}={f001_012,f013_024,f025_036,f037_048,f049_060,f061_072,f
073_0
84,f085_096}, and tCCz is forecast cycle: CC = 12


- A new type source "HMIFR" is used for these STOFS-3D-Atlantic SHEF
files:

stofs_3d_atl.tCCz.points.cwl.shef

Where tCCz is forecast cycle: CC = 12


A consistent parallel feed of STOFS v2.1.7 data is available on the
NCEP
sites at the following URLs:

https://nomads.ncep.noaa.gov/pub/data/nccf/com/stofs/para/
https://www.ftp.ncep.noaa.gov/data/nccf/com/stofs/para/
ftp://ftp.ncep.noaa.gov/pub/data/nccf/com/stofs/para/
https://para.nomads.ncep.noaa.gov/pub/data/nccf/noaaport/stofs_2d_glo
/

NCEP urges all users to ensure their decoders can handle changes in
content order, changes in the scaling factor component within the
product
definition section (PDS) of the GRIB files, and volume changes. These
elements may change with future NCEP model implementations. NCEP will
make
every attempt to alert users to these changes before implementation.








For questions concerning science changes, please contact:
Greg Seroka
Coastal Marine Modeling Branch
Coast Survey Development Laboratory
NOAA/NOS/Office of Coast Survey
Silver Spring, MD
gregory.seroka@noaa.gov

For questions regarding the data flow aspects of these datasets,
contact:
Tony Salemi
NCEP Central Operations Dataflow Team Lead (Acting)
College Park, Maryland
ncep.pmb.dataflow@noaa.gov

National Service Change Notices are online at:

https://www.weather.gov/notification/


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