The zones and areas in this Annex are, in general, based
on the following criteria:
Summer - not more than 10 percent winds of force 8 Beaufort
(34 knots) or more.
Tropical - not more than 1 percent winds of force 8 Beaufort
(34 knots) or more. Not more than one tropical storm in 10 years in
an area of 5° square in any one separate calendar month.
In certain special areas, for practical reasons, some degree
of relaxation has been found acceptable.
A chart is attached
to this Annex to illustrate the zones and areas defined below.
Chart 1. Chart of Zones and Seasonal Areas