Public Information Statement
Issued by NWS National HQ

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
NOUS41 KWBC 031230

Service Change Notice 16-03
National Weather Service Headquarters, Washington, DC
830 AM EDT Tue May 3 2016

TO:   Subscribers:
   -NOAA Weather Wire Service
   -Emergency Managers Weather Information Network
   -Other NWS partners and NWS employees

FROM:   Robyn Heffernan
   Acting Chief, Severe, Fire, Public and Winter Services

   Eric Christensen
   Acting Chief, Marine, Tropical, and Tsunami Services

SUBJECT:   Improved warning polygons along complex coastal
   boundaries effective May 10, 2016

Effective May 10, 2016, the NWS will complete enhancements to the
product generation software used to draw warning threat areas
(polygons) along complex coastal boundaries. This change allows a
buffer along land-marine boundaries. Small scale details of a
coastline are no longer mapped and fewer polygon vertices are
needed. This change only affects the appearance of the polygon.
There is no change to product formats, and users do not have to
take any actions.

Special Marine Warning (SMW) and the follow-up Marine Weather
Statement (MWS) polygons will be drawn slightly further into land
zones than in the past, particularly along complex coastlines.

Similarly, polygons for Tornado Warnings (TOR), Severe Thunderstorm
Warnings (SVR), Flash Flood Warnings (FFW), Flood Warnings (FLW),
Special Weather Statements (SPS) and the corresponding follow-up
Severe Weather Statements (SVS), Flash Flood Statements (FFS), and
Flood Statements (FLS) will be drawn slightly farther into marine
zones than in the past.

This change will improve warning polygons along complex coastal
boundaries of the Atlantic and Pacific Oceans, Gulf of Mexico and
Great Lakes. This change will not apply to warning polygons along
complex inland County Warning Area boundaries, such as along the
Mississippi River.

More information and several examples can be found at:

For more information, please contact:

 John Ferree
 NWS Severe Storms Services Leader

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.