214
NOUS41 KWBC 281240
PNSWSH

Service Change Notice 25-31
National Weather Service Headquarters Silver Spring MD
840 AM EDT Fri March 28 2025

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

From: Judy Ghirardelli
 NWS Office of Science and Technology Integration
 Meteorological Development Laboratory

Subject: Probabilistic Tropical Cyclone Storm Surge (P-Surge)
Model Upgrade: Effective April 29, 2025

Effective on or about April 29, 2025, starting with the 1200
Coordinated Universal Time (UTC) cycle, the National Centers
for Environmental Prediction (NCEP) will upgrade the
Probabilistic Tropical Cyclone Storm Surge model (P-Surge) to
version 3.1.

P-Surge is based on an ensemble of Sea, Lake, and Overland
Surges from Hurricanes (SLOSH) model runs which are derived from
the National Hurricane Center (NHC) official advisory along with
NHC`s historical errors in forecasts of the storm`s track, size,
and intensity.P-Surge currently is run on a case-by-case basis
in advance of hurricanes and tropical storms that may impact the
Atlantic and Gulf Coasts of the Contiguous United States (CONUS)
as well as for storms that may impact Puerto Rico and the U.S.
Virgin Islands.  With this implementation, P-Surge will be able
to be run for Hawaii.

P-Surge version 3.1 includes the following updates:

  A. Creation of P-Surge products for Hawaii that account for
surge, tide, and waves, similar to the P-Surge products
available for Puerto Rico and the U.S. Virgin Islands.P-Surge
products for the CONUS only account for surge and tide.  This
implementation represents the first time that P-Surge will
provide guidance for the Hawaii domain.
  B. More efficient calculation of waves which reduces the
processing time for Puerto Rico and the U.S. Virgin Islands
products.
  C. Discontinuing the probability of > 0 feet above ground
level products for the CONUS and Puerto Rico / U.S. Virgin
Islands domains.
  D. Various code optimizations.

Dissemination Changes:

NCEP NOMADS and FTPPRD web services:
There will be no change to the directory structure on NOMADS and
FTPPRD.  All data from CONUS, Puerto Rico / U.S. Virgin Islands,
and Hawaii products will be present in the same directory:
https://nomads.ncep.noaa.gov/pub/data/nccf/com/psurge/prod/
ftp://ftpprd.ncep.noaa.gov/data/nccf/com/psurge/prod/

However, we are introducing Hawaii GRIB2 files, which will have
"hawaii_312p5m" (vs "conus_625m" for CONUS or "puertori_625m"
for Puerto Rico / U.S. Virgin Islands) in their file names.

Examples of new NOMADS/FTPPRD Hawaii GRIB2 filenames:

psurge.tYYYMMDDHHz.BB##YYYY_eEE_cum_agl.h102.hawaii_312p5m.grib2
psurge.tYYYMMDDHHz.BB##YYYY_eEE_inc_agl.h102.hawaii_312p5m.grib2
psurge.tYYYMMDDHHz.BB##YYYY_gtF_cum_agl.h102.hawaii_312p5m.grib2
psurge.tYYYMMDDHHz.BB##YYYY_gtF_inc_agl.h102.hawaii_312p5m.grib2
  (where YYYYMMDDHH is the date and hour,
  BB## is the storm number,
  YYYY is the year,
  EE is the exceedance above ground level (10, 20, 30,
  40, 50, 90), and
  F is the feet above ground level (1, 2, 3, ..., 20))

psurge.tYYYMMDDHHz.BB##YYYY_eEE_cum_dat.h102.hawaii_312p5m.grib2
psurge.tYYYMMDDHHz.BB##YYYY_gtF_cum_dat.h102.hawaii_312p5m.grib2
  (where YYYYMMDDHH is the date and hour,
  BB## is the storm number,
  YYYY is the year,
  EE is the exceedance above datum (10, 20, 30, ...,
90),
  and
  F is the feet above datum (1, 2, 3, ..., 20))

psurge.tYYYMMDDHHz.BB##YYYY_eEE_inc_dat.h102.hawaii_312p5m.grib2
  (where YYYYMMDDHH is the date and hour,
  BB## is the storm number,
  YYYY is the year, and
  EE is the exceedance above datum (10, 20, 30, 40, 50,
  90))

Additionally, we are introducing shapefiles, which will have
suffixes of "HI.zip" (vs ".zip" for CONUS or "PR.zip" for Puerto
Rico / U.S. Virgin Islands) in their filenames.

Examples of the new NOMADS/FTPPRD Hawaii shapefile filenames:

shpfiles/psurge_tYYYYMMDDHHz_BB##YYYY_eEE_cum_agl_HI.zip
shpfiles/psurge_tYYYYMMDDHHz_BB##YYYY_eEE_inc_agl_HI.zip
shpfiles/psurge_tYYYYMMDDHHz_BB##YYYY_gtF_cum_agl_HI.zip
shpfiles/psurge_tYYYYMMDDHHz_BB##YYYY_gtF_inc_agl_HI.zip
  (where YYYYMMDDHH is the date and hour,
  BB## is the storm number,
  YYYY is the year,
  EE is the exceedance above ground level (10, 20, 30,
  40, 50, 90), and
  F is the feet above ground level (1, 2, 3, ..., 20))

shpfiles/psurge_tYYYYMMDDHHz_BB##YYYY_eEE_cum_dat_HI.zip
shpfiles/psurge_tYYYYMMDDHHz_BB##YYYY_gtF_cum_dat_HI.zip
  (where YYYYMMDDHH is the date and hour,
  BB## is the storm number,
  YYYY is the year,
  EE is the exceedance above datum (10, 20, 30, ... 90),
  and
  F is the feet above datum (1, 2, 3, ..., 20))

We are discontinuing the probability of greater than zero feet
above ground level products.

Examples of NOMADS/FTPPRD files being removed:

psurge.tYYYYMMDDHHz.BB##YYYY_gt0_cum_agl.h102.conus_625m.grib2
psurge.tYYYYMMDDHHz.BB##YYYY_gt0_inc_agl.h102.conus_625m.grib2
psurge.tYYYYMMDDHHz.BB##YYYY_gt0_cum_agl.h102.puertori_625m.grib
2
psurge.tYYYYMMDDHHz.BB##YYYY_gt0_inc_agl.h102.puertori_625m.grib
2
shpfiles/psurge_tYYYYMMDDHHz_BB##YYYY_gt0_cum_agl.zip
shpfiles/psurge_tYYYYMMDDHHz_BB##YYYY_gt0_inc_agl.zip
shpfiles/psurge_tYYYYMMDDHHz_BB##YYYY_gt0_cum_agl_PR.zip
shpfiles/psurge_tYYYYMMDDHHz_BB##YYYY_gt0_inc_agl_PR.zip
  (where YYYYMMDDHH is the date and hour,
  BB## is the storm number, and
  YYYY is the year)

NOAAPORT/SBN:
The products are available over the SBN and NOAAPORT in GRIB2
format.  A complete list of WMO Header IDs for the products can
be found online at the top of the Meteorological Development
Laboratory`s storm surge technical notices here:
https://vlab.noaa.gov/web/mdl/storm-surge-technical-notices

or more directly at:
https://vlab.noaa.gov/documents/6609493/7858383/Mar2025-P-Surge-
v3.1-Headers-Actual.pdf/4c5385e0-d176-c94f-9dc0-
7ef999c931c5?t=1743002554830

Note, due to bandwidth limitations, some of the products on
NOMADS/FTPPTRD are not disseminated over the SBN.  The SBN will
contain the following:

6-hourly cumulative and incremental products to 102 hours:
  A. (10, 20, 30, 40, 50, 90)% exceedance above ground level
  B. Probability of > (1, 2, 3, ..., 10) feet above ground
level

102-hourly cumulative products:
  A. (10, 20, 30, 40, 50, 90)% exceedance above datum
  B. Probability of > (2, 3, 4, ..., 15) feet above datum

We are discontinuing the probability of > 0 feet above ground
level products.  The GRIB2 products have a WMO header scheme of
"T1-T2-A1-A2-i-i CCCC" described here:
https://vlab.noaa.gov/documents/6609493/7858383/Mar2025-P-Surge-
v3.1-Headers-Scheme.pdf/374cd7a8-096b-6aff-59d5-
f0ce4985c7e9?t=1743002561991

In that scheme T2=C or D and A1=A indicates a "Probability of
Surge > 0 feet above ground level," so those products will no
longer be generated.  Specifically for CCCC=KWEV T1=Y or Z, and
CCCC=KWEW T1=Z the following T2-A1-A2-i-i headers will no longer
be generated:

CAB03, CAB09, CAB15, CAB21, CAC03, CAC09, CAC15, CAC21,
CAD03, CAD09, CAD15, CAD21, CAE03, CAE09, CAE15, CAE21,
CAF03, CAF09, CAF15, CAF21

DAB03, DAB09, DAB15, DAB21, DAC03, DAC09, DAC15, DAC21,
DAD03, DAD09, DAD15, DAD21, DAE03, DAE09, DAE15, DAE21,
DAF03, DAF09, DAF15, DAF21

Several canned test runs will be available for testing.  The
data will be hosted on the NCEP HTTPS sites at the following
URLs when they are available, although they may not be present
for the entire 30-day period:
https://nomads.ncep.noaa.gov/pub/data/nccf/com/psurge/para/
https://ftp.ncep.noaa.gov/data/nccf/com/psurge/para/
https://ftpprd.ncep.noaa.gov/data/nccf/com/psurge/para

NCEP encourages users to ensure their decoders are flexible and
are able to adequately handle changes in content order, changes
in the scaling factor component within the product definition
section (PDS) of the GRIB files, and any volume changes that may
be forthcoming.  These elements may change with future NCEP
model implementations.NCEP will make every attempt to alert
users to these changes prior to any implementations.

Any questions, comments or requests regarding this
implementation should be directed to the contacts below.  We
will review any feedback and decide whether to proceed.

For questions regarding the science changes, please contact
Arthur Taylor
Meteorological Development Laboratory
Arthur.Taylor@noaa.gov

For questions about the dataflow aspects, please contact:
Margaret Curtis
NCEP Central Operations HPC Dataflow Team Lead
ncep.pmb.dataflow@noaa.gov

National Service Change Notices are online at:
https://www.weather.gov/notification/