Sailing Weather

Sailing weather watching

Sailing Weather

Weather can sometimes change quickly out at sea, so weather reports and personal observation will be invaluable when reading the signs. When undertaking a sailing course, the instructor will have first-hand knowledge gained from personal experience about the sailing weather conditions likely to be expected.
There is probably some truth to the saying ‘red sky at night, sailors delight; red sky in morning, sailor’s warning’, for an evening red sky is said to be caused by light reflecting off dust particles trapped by high pressure from the west, which may mean good weather to come. The morning red sky however, is thought to be caused by light reflecting off water vapor in high cirrus clouds, which could indicate a weather front approaching.

Sailing weather clouds video

Clouds

Cirrus cloud - sailing weather

Cirrus cloud - Photo by Piccolo Namek

Cirrostratus cloud - sailing weather

Cirrostratus cloud - Photo by Fir0002

Cirrostratus cloud-sailing weather

Cirrostratus cloud - Photo by Simon Eugster

Cirrus

Cirrus clouds are often called ‘mare’s tails’ due to their wispy, threadlike appearance. Made of ice crystals, they may be a sign of a weather front approaching.

Cirrostratus

Cirrostratus clouds are also made of ice crystals. Forming thin veil-like layers, they may be a sign that rain is on its way.

Cumulus cloud - sailing weather

Cumulus cloud - Photo by Picolo Namek

Cirrocumulus cloud - sailing weather

Cirrocumulus cloud- Photo by King of Hearts

Cumulonimbus cloud - sailing weather

Cumulonimbus cloud Photo by Googie Man

 

 

Cumulus

Cumulus clouds are fluffy white clouds that commonly indicate fine sailing weather, however if clouds get bigger and darker thunderstorms may develop.

Cirrocumulus (Mackerel Sky)

– Thin white wisps with a hint of fluffy white, cirrocumulus clouds are a sign of fine sailing weather to come.

Cumulonimbus

Cumulonimbus form from cumulus clouds and are usually a sign that squalls are approaching. Squalls often come line after line, bringing gusty winds and quick, but heavy, rain.

Winds

Winds can be explained simply: hot air rises creating low pressure on the Earth’s surface while cold air falls, causing high pressure. The airflow from high to low pressure creates wind. During your sailing course, you will notice how the boat behaves in different wave conditions. Importantly, we must be prepared for changes in weather so that the sails can be trimmed early and correctly.

British Naval Officer Sir Francis Beaufort observed visual signs out at sea in order to estimate wind conditions. Essentially, wave speed, height and appearance are listed and provide a measure of the wind forces up to 8, according to the Beaufort Wind Scale table.

Beaufort Wind Scale

No Description Wind speed knots Appearance
Approximate wave height (meter)
0 Calm < 1 Sea like a mirror 0
1 Light airs 1 to 3 Ripples like scales Less than 0.1
2 Light breeze 4 to 6 Small wavelets; unbroken crests 0.1 to 0.3
3 Gentle breeze 7 to 10 Large wavelets; maybe white horses 0.3 to 0.9
4 Moderate breeze 11 to 16 Longer small waves; frequent white horses 0.9 to 1.5
5 Fresh breeze 17 to 21 Moderate waves; many white horses 1.5 to 2.5
6 Strong breeze 22 to 27 Large waves; white foam crests, spray 2.5 to 4
7 Near gale 28 to 33 Sea heaps up; waves break, foamy 4 to 6
8 Gale 34 to 40 Moderately high, long waves; crests break, foam streaks 6 to 8
9 Strong gale 41 to 47 High waves. Dense foam. Large amounts of airborne spray. 7 to 10
10 Whole gale 48 to 55 Very high waves, overhanging crests, large patches of foam, sea has a white appearance, airborne spray reduce visibility. 9 to 12.5
11 Violent storm 56 to 63 Exceptionally high wavesand very large patches of foam, very large amounts of airborne spray severely reduce visibility. 11.5–16
12 Hurricane force 64 < Huge waves, sea is completely white with foam and spray, air filled with driving spray, greatly reducing visibility. 14 up

 

Aneroid Barometer

Aneroid Barometer

Barometers

Barometers measure atmospheric pressure and a drop or rise in pressure indicates a change in weather. Ranging from about 960 millibars to 1040 millibars, low pressure indicates bad sailing weather while high pressure indicates fine sailing weather. The rate at which pressure rises and falls can also give an indication of the change coming, for example, cyclones cause a rapid fall in pressure.

Sailing Weather forecasts

During your sailing course you will discover the many forecast sources available for you to check before going out to sea, and even while underway. Local television, radio and newspapers are good sources of sailing weather information, and marinas, sailing clubs and harbor masters offices usually post up-to-date sailing weather forecasts. Local sailors or fishermen will also be an invaluable source of sailing weather information, especially tides and local anomalies.

Bad weather

Fog

Collision is the greatest danger in fog, so skipper and crew need to be alert in fixing the boat’s position using visible landmarks. While sailing courses are usually undertaken in whatever weather is given, it pays to be aware of different conditions and to listen also to the sound of other boats and signals. Even in good visibility, fog can descend without warning, so put on the navigation lights, and keep the boat’s course and speed steady.

Gales

When experiencing gales out at sea, it is important to reduce the mainsail area early and quickly by reefing. It is a good idea to practice reefing in calm weather on your sailing course so if the need arises you will know what to do. Reducing the sail area in weather like this keeps the boat under control. It is also likely that the skipper will decide to hoist a small head sail, such as a storm jib, to keep the boat steady and maintain speed. As always, decks need to be kept clear and hatches securely shut. There may also be more motion, so sea sickness pills, food and beverages should be on hand and easily accessible.

Lee shore

A lee shore is a dangerous place to be in bad weather, as a strong onshore wind can blow the boat quickly towards the coast line, meaning the chance of running aground in shallow waters, and possible hazards such as reef and rocks. Heavy seas can build up quickly in shallow waters, so it is a good idea to stay out at sea rather than risk a hazardous anchorage or harbor approach. The risks and solutions will be explained during your sailing course so that you can be prepared for any action that needs to be taken.

Sailing Weather Summary

In all it is a very important task to check the sailing weather forecast and be always prepared for possible bad sailing weather.


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