NOUS41 KWBC 141450 Updated



Service Change Notice 17-30

National Weather Service Headquarters Silver Spring, MD

950 AM EDT Tue Mar 14 2017


To:       Subscribers:

          -NOAA Weather Wire Service

          -Emergency Managers Weather Information Network


          Other NWS Partners, Users and Employees


From:     Allison Allen

          Chief, Marine, Tropical, and Tsunami Services Branch


Subject:  Updated: Changes to the Graphical Tropical Weather

          Outlook (GTWO) issued by the National Hurricane Center   

          effective on or around May 15, 2017


Updated to change from Public Information Statement to Service

Change Notice


Effective on or about May 15, 2017, the content of the Graphical

Tropical Weather Outlook (GTWO) issued by the National Hurricane

Center (NHC) will be modified. The majority of the changes have

been necessitated to accommodate potential tropical cyclones. 

A potential tropical cyclone is a disturbance that is not yet a

tropical cyclone, but one for which the NWS has begun issuing

tropical cyclone watches or warnings because it poses the threat

of bringing tropical storm or hurricane conditions to land areas

within 48 hours.


Summary of changes:


1. The current location of all active tropical cyclones will be

included on the 5-day GTWO.


2. The current location of potential tropical cyclones will be

included on the 2-day and 5-day GTWO.  


3. The current location of the potential tropical cyclones will

be depicted by an x, with the number of the potential cyclone

(e.g., One) displayed above the x. The x will be color coded

based on the forecast likelihood of tropical cyclone formation

during the 2- or 5-day period corresponding to that graphic:


- Yellow, 30 percent or less chance

- Orange, 40-60 percent chance

- Red, 70 percent or greater chance


A swath showing the forecast development area of the potential

tropical cyclone will not be shown on the 5-day GTWO to avoid

confusion with the existing 5-day track forecasts that will be

provided for those systems.


4. The current location of potential tropical cyclones will not

be included in the shapefile that accompanies each issuance of

the GTWO. Users will be directed to the shapefiles accompanying

the full forecast advisory for potential tropical cyclones.  The

forecast advisory shapefiles will include the current location

and forecast track of the potential tropical cyclone.


If you have questions or comments please contact:


Jessica Schauer

NWS Marine, Tropical and Tsunami Services Branch

Miami, FL 33165

Telephone: 305-229-4476



John Kuhn

Meteorologist, Marine, Tropical, and Tsunami Services Branch

Silver Spring, MD





NWS Service Change Notice are online at: