NOUS41 KWBC 091955



Service Change Notice 17-28

National Weather Service Headquarters Silver Spring MD

355 PM EST Thu Mar 9 2017


To:      Subscribers:

         -NOAA Weather Wire Service

         -Emergency Managers Weather Information Network


         Other NWS Partners and NWS Employees


From:    Allison Allen

         Chief, Marine, Tropical and Tsunami Services Branch


Subject: Changing criteria for issuing tropical cyclone watches

         and warnings to include certain land-threatening

         disturbances that are not yet tropical cyclones

         effective on or about May 15, 2017


Beginning on or about May 15, 2017, the NWS will have the option

to issue watches, warnings, and graphical and textual advisory

products for disturbances that are not yet tropical cyclones,

but which pose the threat of bringing tropical storm or

hurricane conditions to land areas within 48 hours. Under long

standing policy, the NWS has not been permitted to issue a

hurricane or tropical storm watch or warning until after a

tropical cyclone had formed. Advances in forecasting over the

past decade now allow the confident prediction of tropical

cyclone impacts while these systems are still in the

developmental stage. 


For these land-threatening "potential tropical cyclones," the

NWS will now issue the full suite of products that previously

has been issued only for ongoing tropical, subtropical or 

post-tropical cyclones. In addition, the NWS will begin issuing

watches and warnings for storm surge associated with tropical

cyclones threatening the Atlantic and Gulf coasts of the

contiguous United States in 2017 and will have the ability to

issue these watches and warnings for potential tropical cyclones

as well. The Potential Storm Surge Flooding Map and Storm Surge

Watch/Warning graphic will also be issued for these systems when



Potential tropical cyclones will share the naming conventions

currently in place for tropical and subtropical depressions,

with depressions and potential tropical cyclones being numbered

from a single list (e.g., One, Two, Three, ..., Twenty-Three,

etc.). The assigned number will always match the total number of

systems (tropical cyclones, subtropical cyclones, or potential

tropical cyclones) that have occurred within that basin during

the season. 


For example, if three systems requiring advisories have already

formed within a basin in a given year, the next land-threatening

disturbance would be designated Potential Tropical Cyclone Four.

If a potential tropical cyclone becomes a tropical depression,

its numerical designation remains the same (i.e., Potential

Tropical Cyclone Four becomes Tropical Depression Four).


The issuance times for potential tropical cyclone products will

be identical to the standard tropical cyclone product issuance

times. NWS products for potential tropical cyclones will be

issued until watches or warnings are discontinued or until the

wind and storm surge, if applicable, threat for land areas

sufficiently diminishes, at which point advisories would be

discontinued. If, however, it seems likely that new watches or

warnings would be necessary within a short period of time (e.g.,

6-12 hours), then advisories could continue briefly in the

interest of service continuity. Once a system becomes a tropical

cyclone, the normal procedure for discontinuing advisories will

apply. Potential tropical cyclone advisories will not be issued

for systems that pose a threat only to marine areas.


Because NHC and the Central Pacific Hurricane Center will be

issuing their normal graphical products depicting the 5-day

forecast track and uncertainty cone for potential tropical

cyclones, the Graphical Tropical Weather Outlook will no longer

display a formation area for these systems to avoid confusion.


If you have questions, please contact:


Jessica Schauer

NWS Marine, Tropical and Tsunami Services Branch

National Hurricane Center

Miami, FL 33165

Telephone: 305-229-4476



Wayne Presnell

NWS Marine, Tropical and Tsunami Services Branch

Silver Spring, MD  20910

Telephone: 301-427-9390



National Service Change Notices are online at: