NOUS41 KWBC 311655



Technical Implementation Notice 15-16

National Weather Service Headquarters Washington DC

1255 PM EDT Tue Mar 31 2015


To:       Subscribers:

         -Family of Services

         -NOAA Weather Wire Service

         -Emergency Managers Weather Information Network


         Other NWS users and employees


From:    Mark Tew

         Chief, Marine and Coastal Services Branch


Subject: Tropical Cyclone Threat Grids in the National Digital

         Forecast Database will Transition to Operational

         Effective June 1, 2015


Effective June 1, 2015, the Tropical Cyclone Threat Grids in the

National Digital Forecast Database (NDFD) will transition from

experimental to operational. 


The Tropical Cyclone (TC) Threat grids consist of four elements:

- Wind

- Storm surge

- Flooding rain

- Tornado


There are five levels to describe each TC Threat grid:

- Little to None (changed to add Little)

- Elevated (changed from Low)

- Moderate

- High

- Extreme


The TC Threat elements provide the reasonable worst case

scenario, taking into account the forecast magnitude of the

hazard, along with the associated uncertainty of the forecast. 

The elements are produced only by coastal WFOs along the Atlantic

and Gulf coasts and by San Juan, PR, whenever tropical cyclone

watches and warnings are in effect for their area of

responsibility (AOR).


Because the grids do not convey specific timing, they are valid

for the duration of the event. Updates will be provided at least

every 6 hours shortly after the National Hurricane Center's

advisory, and will cease when tropical cyclone watches and

warnings are no longer in effect for a WFOs AOR.


Additional details regarding these grids are available in the

Product Description Document at:


The TC Threat grids will be available from NDFD in the following

standard methods:


- Gridded Binary Version 2 (GRIB2) files via Hypertext Transfer

  Protocol (HTTP) and File Transfer Protocol (FTP)

- Extensible Markup Language (XML) via Simple Object

- Access Protocol (SOAP)

- Graphics via web browser


Users who pull NDFD elements in GRIB2 format, either via the

Internet or via the Family of Services (FOS) server, may need to

update their procedures and scripts in order to access these new

elements.  The GRIB2 files are available online at:


CONUS Sector


Puerto Rico Sector


with the following file names used: 


Wind                ds.tcwt.bin

Storm Surge         ds.tcsst.bin

Flooding Rain       ds.tcfrt.bin

Tornado             ds.tctt.bin


For Users who key on the World Meteorological Organization (WMO)

super heading to access NDFD elements, the super headings are:


Geographical Area   Threat Element   WMO Header


CONUS               Wind             ZWUZ98 KWBN

CONUS               Storm Surge      ZSUZ98 KWBN

CONUS               Flooding Rain    ZFUZ98 KWBN

CONUS               Tornado          ZYUZ98 KWBN

Puerto Rico         Wind             ZWAZ98 KWBN

Puerto Rico         Storm Surge      ZSAZ98 KWBN

Puerto Rico         Flooding Rain    ZFAZ98 KWBN

Puerto Rico         Tornado          ZYAZ98 KWBN


Graphics for the threat grids will be available at:


Information on accessing and using NDFD elements is online at:


For general questions regarding NDFD data, please email:


For technical questions regarding NDFD data, please contact:


  David Ruth

  Mesoscale Prediction Branch Chief

  NOAA/NWS Office of Science and Technology

  Silver Spring, Maryland



If you have questions regarding this notice, please contact:


  John F. Kuhn

  Marine and Coastal Weather Services   

  National Weather Service Headquarters

  Silver Spring Maryland 20910



Technical Implementation Notices specifically related to NDFD are online at:


National Technical Implementation Notices are online at: