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NOUS41 KWBC 311725

Service Change Notice 16-36
National Weather Service Headquarters, Washington, DC
125 PM EDT Wed Aug 31 2016

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

FROM:   John Ferree
   Acting Chief, Severe, Fire, Public and Winter Weather
   Services Branch

   Tim Oram
   Acting Chief, Marine, Tropical and Tsunami Services

SUBJECT:   Tornado and Severe Thunderstorms Watches May Include
   Outer Marine Zones Effective September 29, 2016

Effective Thursday, September 29, 2016, at 1800 Coordinated
Universal Time (UTC), Continental U.S. Tornado and Severe
Thunderstorm Watches may include outer marine zones. Currently
Tornado and Severe Thunderstorm watches can only include the near-
shore marine zones, out to approximately 20 miles off-shore. This
change allows watches to extend to the outer marine zones, to
approximately 60 miles off-shore.

Inclusion of the outer marine zones in some Tornado and Severe
Thunderstorm Watches will give a more complete understanding of the
severe thunderstorm risk to mariners, particularly in the Gulf of
Mexico and off the Atlantic Coast. Tornado Watches and Severe
Thunderstorm Watches will only include the outer marine zones when
the adjacent near-shore marine zones are included in the watch.

This change only affects Tornado Watches and Severe Thunderstorm
Watches. Warnings are not impacted by this change, and only Special
Marine Warnings will continue to be issued in these outer marine
zones. There is not a change to product formats.

Maps of the inner and outer coastal marine zones around the
CONUS are posted at

(click marine coastal areas for detail).

These zones are described further in NWS Instruction 10-302
found at:

List of additional marine zones potentially included in a tornado
or severe thunderstorm watch:

GMZ170   ANZ070     AMZ170 PZZ170
GMZ175   ANZ071     AMZ172 PZZ173
GMZ270   ANZ170     AMZ174 PZZ176
GMZ275   ANZ172     AMZ176 PZZ270
GMZ370   ANZ174     AMZ178 PZZ275
GMZ375   ANZ270     AMZ270 PZZ370
GMZ470   ANZ271     AMZ272 PZZ376
GMZ472   ANZ272     AMZ274 PZZ470
GMZ475   ANZ273     AMZ276 PZZ475
GMZ570   ANZ370     AMZ370 PZZ570
GMZ572   ANZ373     AMZ372 PZZ571
GMZ575   ANZ375     AMZ374 PZZ575
GMZ577   ANZ470     AMZ470 PZZ576
GMZ670   ANZ471     AMZ472 PZZ670
GMZ675   ANZ472     AMZ474 PZZ673
GMZ770   ANZ473     AMZ570 PZZ676
GMZ775   ANZ475     AMZ572 PZZ775
GMZ870   ANZ670     AMZ575
GMZ873   ANZ672     AMZ670
GMZ876   ANZ674     AMZ671
GMZ676   ANZ676
GMZ033   ANZ678

For more information, please contact:

John Ferree
Severe Storms Services Leader
Telephone: (405) 325-2209

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