Boating 101: Interpreting Wave Forecasts

Checking and interpreting wave forecasts proves critical to safety and comfort.

First, let me plead, “Mea culpa.” I’ll admit to fixating on marine wind forecasts before venturing out to sea, sometimes to the exclusion of wave projections. That shortcut has more than once come back to bite me in the stern quarters.

While wind has a major effect on sea conditions, boaters need to pay attention to other elements outlined in the marine forecast and how they translate to real-life conditions at sea.

Wave Check

Planning an ocean trip without reviewing the wave forecast can lead to startling and uncomfortable surprises, as it did for me one windless morning in spring as we headed out the inlet of Mission Bay in San Diego. Had I checked the wave forecast, I would have known that a healthy lump generated by a spring gale far out in the Pacific was rolling in from the west.

As waves approached the shallows at the west-facing cut, they rose up and closed ranks like menacing demons, with steep 6- to 7-foot faces and cresting tops. Our 21-footer made it out, but the experience certainly ramped the pucker factor and required careful throttle work to climb each wave without launching and slamming hard on the back side before facing the next one and eventually escaping the danger zone.

Had I checked the wave forecast, I might have decided to launch the boat a mile down the coast in San Diego Bay, which has a much wider opening, a deeper channel and faces south, so it’s less vulnerable to a lump out of the west.

Fortunately, the waves mellowed out during the course of the day, so the return to Mission Bay was not nearly as gnarly as the exit. But the lesson here is to pay close attention to the wave forecast as well as the projected winds.

Interval Influence

Not all waves are created equal, even those of equal size. If that sounds like double talk, bear in mind that the interval between the waves has a major effect on sea conditions. For example, 3- to 4-foot waves that roll in about 12 seconds apart prove far more friendly than waves of the same height that are four to five seconds apart…