THE FICKLE FOE

Lightning is a violent and powerful force of nature. Of all the perils sailors face at sea, lightning is one of the most dangerous and it is highly unpredictable and far more common than you might think. Although a lightning bolt may last only milliseconds, a direct hit on an unprotected boat can cause catastrophic damage. There is no ‘safe’ place for a boat in a thunderstorm and sometimes lightning just can’t be avoided, but it is possible to take precautions against a bad outcome.

LIGHTNING 101

Lightning is usually produced by cumulonimbus clouds, huge formations with bases typically 1–2km above the ground, rising as much as 15km to flattened, anvil-shaped tops. Within them, warm, moisture-laden air rises rapidly, cooling and condensing into water vapour the higher it goes. The denser cold air falls and may leave the cloud as rain, or it may reheat and rise again to repeat the process. This turbulent cycle produces ‘charge separation’, an electrostatic imbalance in which positive ions gather near the top of the cloud, leaving negatively charged particles near the bottom. As the negative charge increases, it induces an accumulation of opposite, positive charge on the surface of the