Chapter 5 Weather

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This chapter covers what yachtsmen need to know about the weather.

Weather is an extremely important factor in boating and yachting, and it is vital that the skipper is equipped to make decisions such as whether to go to sea, whether to put in to shelter or whether to carry on.

This necessarily requires practical exposure to different conditions, and experience, and it is not the purpose of this theory class to impart these things. Instead we give you the theoretical knowledge you need to be able to interpret weather forecasts, and to some extent the weather itself.

This chapter contains two main sections:

a) weather forecasts - how to get them, and what they mean

b) weather features and what their effect is: a basic guide to understanding what is going on with the weather.

Aspiring Day Skippers will probably need to concentrate on the first of these.

I am do not intending to cover world-wide climate and weather in this chapter, and most of the explanations are unashamedly "UK-oriented" (although naturally much of it applies everywhere in the world). Nor do I intend to discuss conditions that we never get in the UK, such as sea ice and Tropical Revolving Storms (aka Hurricanes).

Weather is a limitless and fascinating subject, and well worth further study. There are many books on the weather knowledge for yachtsmen, and I would recommend a browse in the bookshop, because depending on your level of understanding of the science, you may find some more useful than others.

The Met Office HMSO publication "Meterology for Mariners" is a particularly useful and authoritative publication: it's relatively advanced, but full of good information, and covers world-wide climate and weather. (I had a copy on board when I did my first long distance sailing trip. Of course I hadn't read it all beforehand, and each new and unfamiliar weather event had us scurrying for the book and frantically mugging up the relevant chapter.)


Seafarers are notoriously affected by the weather, because it can make a huge difference to the conditions we face at sea. With no exaggeration whatever, the weather can turn a really enjoyable family day out in a boat, into a terrifying, extremely uncomfortable, life-threatening situation.

Added to this, sailors actually rely on one feature of the weather - wind - for their propulsion, so its strength and direction have a great effect on that where we can go.

Our main source of information, and defence against being caught out by bad weather, is the weather forecasts provided for mariners. These are more specialised than the "general weather forecasts" on radio or television broadcasts (which for example rarely mention the direction of the wind). In order to be concise and relevant, forecasts for mariners use a number of terms with specific meanings, and we need to understand those terms in order to benefit from the forecasts.

Besides the forecasts, there is the reality of the weather and the science of what causes it. A small amount of knowledge of this can pay huge dividends when we come to observe what is happening and make decisions accordingly. Sections 3 and 4 of this chapter attempt to open skippers' eyes to some of the readily observable phenomena of the weather and their physical causes. This observation and understanding makes for better interpretation of weather forecasts.