When it comes to sailing, knowing what the wind and sea are doing is everything - and not just for the sailors; organisers and safety crews need to know what to expect in races when yachts and equipment are being pushed right to their limits. There are many elements that affect sailing, including wind direction, wind speed, the state of the sea and also thunderstorms. The type of clothing you wear is also an important element, enabling athletes to perform their best. In this article and video, Penny looks at how weather affects sailing and the best type of clothing to wear when out on the water.

Forecasting weather for Weymouth and Portland

The venue for the Olympic and Paralympic sailing events at Weymouth and Portland is an ideal spot in many ways, but also poses some complexities for the Met Office team who will be forecasting conditions for the races. The Met Office has also been providing LOCOG with detailed historic observational data to support planning for the sailing events, this will decide the positioning of the course, the course markers and their boats.

Typically, measurements are taken before the start of a race to ensure the starting line is 90 degrees to the wind perpendicular to the wind direction. There should be a spread of boats along the line, rather then bunched up at one end, which helps ensure that the start line is unbiased. Bunching up might lead to a messy start, possible disqualifications, restarts and accidents.

Wind direction

Weymouth Bay is sheltered from the predominant westerly and south westerly winds by the Isle of Portland - which is about 4 miles long and 1.5 miles wide. This means the Bay is protected from seas whipped up by these winds, making for better conditions for sailing.

Wind direction is probably the weather element you would most associate with sailing. Most competitive sailors will seek out the most accurate forecast available in order to plan their strategy and tactics before the race. Once the race has started the wind direction becomes less important as sailors have to use their skills to use changes in winds direction or 'shifts' to their advantage.

Wind speed

If the wind is below three or four knots then the boats may not go fast enough to overcome tide and hence the race may not start, be abandoned or may take too long which can also be a problem as races have a time limit. Different speed criteria is used for different boat or windsurfer classes. If the wind speed is too high then there is a danger of broken equipment on board, collisions and accidents, frequent capsizing and health and safety issues for competitors.

State of the sea

The type of waves and swell will have different impacts on the different classes of boat and windsurfer. If waves or swell are too high then boats can become swamped, equipment may be damaged and accidents and collisions can occur.

Thunderstorms

As well as the gusty winds sometimes being associated with thunderstorms, the wind speed may also go above the recommended level for the boat classes. Lightning is also an issue due to most of the masts now being made out of man-made materials such as metal which would act as a classic lightning conductor. Damage can still be sustained to a boat and its crew if a boat is struck by lightning.

Clothing

As well as having to wear a buoyancy aid there are also different types of clothing for the crew to consider. This will be mainly dependant on the weather conditions. For example light clothing in light winds in warmer weather and heavier duty clothing in cold weather and high winds. In particular for dinghy sailors there may also be a consideration on wearing a wet or dry suit and each of these can have an impact on an athletes performance on the day.

You can find out more about how we are using the latest weather forecasting technology to give guidance on the wind and wave conditions for sailors, organisers and safety crews at the Olympic and Paralympic sailing events at Weymouth and Portland during London 2012