http://www.hwn.org/home/net-procedures.html

The Hurricane Watch Net and the operation at WX4NHC at the National
Hurricane Center in Miami are manned entirely by volunteers. We activate
whenever a system has achieved hurricane status and is within 300 miles of
populated land mass or at the request of the National Hurricane Center.

Net operations are conducted on 14.325 MHz, and when band conditions
warrant, we move to 3.950 MHz.