Most of those who earn their living on the water are familiar with the old adage “mackerel scales and mares’ tails cause tall ships to fly low sails." Working far from shore, they know to keep a weather eye to cloud formations that portend incoming storms and a test of their seamanship.
Recreational boaters can avoid boating in bad weather for the most part by checking the marine forecast before heading out and postponing their cruise until the weather improves. But once on the water sudden severe thunderstorms are still a hazard and can materialize out of nowhere. That’s when seamanship—the ability to pilot a vessel effectively under adverse conditions—comes into play. It is a skill acquired over time and involves a broad understanding of your vessel and how it handles in different situations and with varying loads. It also requires knowledge of wind, water and geography, information that can be gained both in the classroom and in on-the-water training. You and your boat need to be prepared at all times. Anchors and rodes should be kept in a state of readiness, along with life jackets and all other safety equipment.
No two storm situations are alike. Many small boats are not designed or constructed to take a heavy pounding and the result can be structural damage that can cause the boat to break apart. In strong breaking waves, flooding and capsizing may occur. In beam seas (waves perpendicular to the side of the boat), excessive roll can cause your load to shift, creating a dangerous list. In following seas (waves coming from behind the boat), your vessel may lose stability on a wave crest; plus, if your speed is excessive, broaching may occur – a situation where the vessel runs down the crest of a wave, gathering speed, and buries its bow into the backside of the next wave. This frequently causes the boat operator to lose control and the vessel to veer sharply off course. In quartering seas, beam and following seas combine to create one of the most serious conditions a boater may encounter.
In a sudden storm, your most immediate problems are limited visibility, high winds and – depending on your location – rapidly building seas. Try to remain calm. Have everyone dress as warmly as possible, put on their life jackets and, if possible, go below.
Close all hatches, doors, watertight compartments and windows to reduce the amount of water taken on board. In an open boat, passengers should sit low in the bottom of the boat along the center line.
Although you need to get your boat to the dock as quickly as possible, once waves reach a certain height, safety dictates that you match the speed of the vessel to the speed of the waves. That means slowing down a lot. The more you reduce speed, the less strain will be put on the hull and superstructure and less risk that portholes and windows will pop out or break. Keep your vessel at a 45-degree angle to the wind and make slow but steady progress to the nearest port.
Stay away from rocky shorelines. If you’re far from port but have shelter available, such as islands and peninsulas, sheltering may be a good idea depending on the depth of the water and the condition of the shoreline. Just bear in mind that in most thunderstorms the wind direction will probably change. In a thunderstorm, winds generally blow outward from the area of heaviest rain. As the storm approaches, winds come straight at you. As it passes overhead, the winds ease off, then reverse direction. Understanding this pattern can give you a reasonable idea of how long you’ll be fighting the storm. In smaller boats, putting up on a sandy beach may be a good idea. If you perceive the situation as life threatening, it's better to sacrifice the boat to save yourself and your family or friends.