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NOUS41 KWBC 091950

Service Change Notice 21-41
National Weather Service Headquarters Silver Spring MD
350 PM EDT Fri Apr 9 2021

To: Subscribers:
 -NOAA Weather Wire Service
 -Emergency Managers Weather Information Network
 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 May 11, 2021

Effective on or about May 11, 2021, 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 2.9.

P-Surge is based on an ensemble of Sea, Lake, and Overland Surge
from Hurricanes (SLOSH) model runs which are derived from the
National Hurricane Center (NHC) official advisory along with
historic errors in its track, size, and intensity.  P-Surge has
historically been run when NHC hurricane watches were in effect
for the Atlantic and Gulf Coasts of the continental United
States (i.e., up to 48 hours before the onset of tropical storm
force winds), and on a case by case basis for tropical storms
too weak to warrant a hurricane watch.P-Surge will now be run
on a case-by-case basis up to 60 hours before the onset of
tropical storm force winds.

P-Surge version 2.9 includes the following updates:

  A. Initialize the wind ensemble members based on an NHC
forecast of the radius of maximum winds rather than assuming
either the storm`s central pressure or size will remain
  B. Expansion of pre-computed tide-only computations, used to
optimize run-times, to November 2023.
  C. Various code optimizations

Dissemination Changes: None

The products are available over the Satellite Broadcast Network
(SBN) and NOAAPORT in GRIB2 format.  A complete list of WMO
Headers for the products can be found online at the top of MDL`s
storm surge technical notices here:

or more directly at:

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

For questions about the dataflow aspects, please contact:

     Anne Myckow
     NCEP Central Operations Dataflow Team Lead

National Service Change Notices are online at: is the U.S. government's official web portal to all federal, state and local government web resources and services.