Why do gusts always arrive from a different direction to the prevailing wind and always seem to head you rather than lift? The wind is never very steady, but given an open stretch of water, any variations in strength tend to be in the same direction as the prevailing wind. Things change, however, in two ways: (1) wind coming from the land, and (2) squalls. Wind is created by differences in air temperature, warm air rising and cooler air rushing in to fill the space left. This happens worldwide as tropical air rises and polar air moves in to fill the vacuum created.

This basic wind pattern is altered by the difference in temperature between land and sea. Air is not really heated by direct sunshine which passes straight through and has very little effect. It does, however, heat up the land very quickly and this in turn heats up the air above it. This hot air rises quickly and as it rises it expands and cools. This cooler air cannot contain the same amount of moisture and condensation occurs in the form of clouds.

Where the wind is passing over land and out to sea, it passes areas of warm land and its pattern varies considerably, leading to strong and variable gusts. In my club, we are on the eastern shore of Southampton Water and it is well recognised that an easterly wind is a hazard to sail in. The wind swirls through trees near the land and gusts offshore and as you try to beat back to shore, it provides great amusement for the barroom sailors to watch people leaping in and out of their boats, trying desperately not to capsize, especially near the clubhouse, where points will be awarded afterwards for style, ingenuity and content.

The other type of gusts come from squalls which are always associated with large black clouds, called cumulo-nimbus, which can grow into the massive anvil shaped storm clouds and can decimate a racing fleet. I well remember as a newcomer to racing, watching all the experienced sailors ahead of me on the beat suddenly turn around and head for shore. When the squall hit, I managed to push my boat head to wind and even hold it there for what seemed like three or four days, but was probably 30-40 seconds, before being pushed flat in the water, losing paddles, buckets, spinnaker poles and spare tools. I now try to tie everything on, but have not found any real answer to the power of these winds.

These great clouds occur in conditions the weather men call ‘unstable air’. The air is cooler the higher you go and the bubbles of hot air rising from the land also cool as they expand. More heat is released by the process of condensation (called Latent Heat), re‑warming the air mass which continues to rise, expand and cool. Often, the air bubble reaches a point where it is the same temperature as the surrounding air and stops rising. You often see this in the effect of the cotton wool balls floating across a summer sky. If, however, the surrounding air is still colder than the air bubble, the hot pocket of air carries on cooling and rising at great speed. The wind continues to blow this great cloud along, the stronger winds at great altitude blowing the top of the cloud out in front to form the ‘anvil’ shape. As it moves, it sucks more warm air into it, which rises, loses moisture and cools down. These tiny drops of condensate are lifted many thousands of feet into the air, becoming supercooled. The cold air then falls quickly at the rear of the cloud carrying moisture with it. As these great stormy black clouds are pushed along by the wind towards your boat, the first thing you notice is that the wind dies and the air is ominously still. The air being sucked into the cloud matches the speed of the wind blowing the cloud along. The light darkens as the huge mass of the cloud blots out the sun and then suddenly, with the speed and power of a locomotive, a huge gust hits you, complete with rain or hail falling from 10,000 ft. It is almost impossible to anticipate which is the best direction to go as the main wind is almost vertically down, only going horizontal as it hits the sea.

If the squall passes to one side of you, you will notice that the wind will start to veer towards the cloud and suddenly return in the opposite direction with great force and a lot of water. I have seen boats going in opposite directions, both on port tack, on opposite sides of a squall.

My own way of dealing with this situation is to harden up sharply until I am ‘pinching’ or slightly nearer head to wind than a normal beat, let off the kicker to spill wind, but don’t free off too much or you simply lose weigh and will capsize. I would be interested to hear from anyone else who has a successful method of dealing with gusts (other than changing crew for one without a stomach problem), as we cope about 75% of the time, but have improved our capsize recovery drill in the remainder. Squalls always happen too quickly to avoid them and even if you do make it to shore, it always hits you just before you get the trolley under the boat. If you are racing, good luck, but if you are cruising, it may be worth putting in a reef before you set sail, but take a bucket anyway. It is very useful to put over your head if it hails!