Documentation on ATCF data formats are maintained by the 
Naval Research Laboratory (NRL) in Monterey, CA.

Updated NRL documentation can be found at the link below:

http://www.nrlmry.navy.mil/atcf_web/docs/database/new/database.html

The National Hurricane Operations Program (NHOP) document also describes
every product produced by the NHC for tropical cyclone forecasting.

The NHOP document is updated once a year. Please see the 2015 NHOP at the link below:

http://www.ofcm.noaa.gov/nhop/15/nhop15.htm