Special recommendations on CAP for tropical storms
In general, we strongly recommend that the <area> element of a CAP alert
represent the geographic area to be notified, not the incident area. In the case
of a tropical storm, this means that the <area> should contain polygons or
geocodes for the places that you expect to be affected by strong winds, heavy
rain, and other threats from the storm. If the storm is still offshore, this
means that the <area> of your CAP alert shouldn't be the storm's current
location.
Instead, you can provide a separate Crisis Map layer
to specify the storm's current location and forecast track. For each current or
predicted storm location, helpful data points to specify in the Crisis Map file
include the time when the storm will be (or is) at that location, the storm
center's latitude and longitude, and an error radius or area of uncertainty.
It's a good idea to describe the storm's location and expected path in your CAP
alert's <description> element, too, for users who prefer reading a textual
description.