Basic Marine Weather
30
Estimating Equations
It actually takes 18 hours
for a 12 second wave to travel 335 nm.
While individual waves travel at ~3.2 T
knots, groups of waves travel at ~(3.2/2)T knots.
This is the group speed which is used to
determine how long it will take a packet of swells to arrive.
The wave speed is the speed your boat would
need to travel at to stay out in front of an individual wave.