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Service Change Notice 24-98
National Weather Service Headquarters Silver Spring MD
915 AM EDT Fri Oct 18 2024

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

From: Greg Schoor, Chief
 Marine, Tropical, and Tsunami Services Branch

Subject: The Coastal Waters Forecast Product from the Weather
Forecast Office (WFO) in Guam Will Include Additional Wave
Information on or about November 4, 2024

The National Weather Service (NWS) Weather Forecast Office (WFO)
in Guam (GUM) will start including wave height, period, and
direction in the Coastal Waters Forecast (CWF) text product for
Guam and the Commonwealth of the Northern Mariana Islands (CNMI)
coastal waters on or about November 4, 2024.

The initial nationwide implementation that did not include Guam
was completed in the Spring of 2024 and can be referenced in
Service Change Notice (SCN) 24-17, with further information
about the changes to the CWF included as a reference.

This implementation will enable WFO Guam to provide the
following enhanced and detailed wave information in the CWF:

1) Significant wave height (mandatory) with ranges (optional):

- Seas 6 ft. (wave height)
- Seas 4 to 6 ft. (wave height with range)

2) Wave detail information - height, period, and direction
(single values) for one or more wave systems:

- Wave Detail: E 4 ft at 5 seconds and NE 2 ft at 13 seconds.

3) The terms "wind wave" and "swell" will no longer be utilized
in the CWF.  While once helpful for describing wave
characteristics before the advent of modern wave models,
continued use of these terms hinders the standardization of more
informative wave terminology, such as height, period, and
direction, produced by wave models.

The Coastal Waters Forecast (CWF) product for WFO Guam can be
found at the following link:

https://forecast.weather.gov/product.php?site=CRH&product=CWF&is
suedby=GUM

Table 1: NWS Office that Will Issue CWF Containing the Wave
Component

WFO   WMO Header   AWIPS ID
----------   ----------   --------
Tiyan, Guam   FZMY50 PGUM   CWFGUM

Further information on the CWF Wave Component can be found in
the Product Description Document available at the following
link:

https://nsdeskdev.servicenowservices.com/api/g_noa/nwspc/res2/d7
f8c71d87111e10fd6c0f280cbb3541

On NWS websites, clicking on coastal areas of the Watches,
Warnings and Advisories (WWA) map will display the marine
forecast with wave details.  However, selecting a point on the
secondary map does not include detailed wave terminology, though
this feature is expected in a future update.

If you have questions or comments, please contact:

Melinda Bailey
NWS National Marine Program Manager
Silver Spring, MD
melinda.bailey@noaa.gov

or

Elizabeth Vickery
Regional Operational Services Meteorologist
NWS Pacific Region Headquarters
Honolulu, HI
elizabeth.vickery@noaa.gov

National Service Change Notices are online at:

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