Weather

By Storm Dunlop

A compact introduction to observing, predicting, and understanding the weather

Note: this ebook for black and white devices was originally created and printed in colour. For this reason, a small number of the illustrations will be difficult to read on a black and white device.

This handy little guide provides the perfect introduction to what is happening in the sky, come rain or shine. Different weather conditions are all illustrated, so you can look through the pictures to identify what you have seen, or if you know the type of cloud or phenomenon that interests you, Gem Weather will tell you much more about it. A helpful glossary explains any technical or scientific terms you may not be familiar with.

The book starts by teaching you how to recognise basic cloud types, and from there some of the variations you may encounter. Becoming familiar with these and understanding why they occur is a practical way to begin making your own weather predictions. Then winds, precipitation, other optical phenomena and weather fronts are all explained, providing all you need to know to understand satellite images and how the weather is forecast. Extreme and severe weather conditions, such as tornadoes and hurricanes, are finally included because they help to illustrate the range of weather events and explain some of the processes that occur in the atmosphere.

All weather conditions, clouds and optical phenomena are fully illustrated with colour photographs, and there are practical explanations of how the weather is forecast and how to read weather maps. This bestselling natural history gem is an ideal pocket reference for budding meteorologists, and an accessible introduction to the subject for beginners of all ages.

• Language: English
• Publisher: HarperCollins UK
• Release date: Apr 12, 2012
• ISBN: 9780007439997

Storm Dunlop

Storm Dunlop is an experienced Astronomy and meteorology author andtranslator. Books include Clouds (Haynes, 2019), Gem Weather (Collins,2012), How to Read the Weather (National Trust, 2018), MeteorologyManual (Haynes, 2014), Practical Astronomy (Philip’s, 2012) and is thelead author for the bestselling annual Guide to the Night Sky (Collins).Fellow of the Royal Astronomical Society, the Royal MeteorologicalSociety and a member of the International Astronomical Union.

Book preview

CLOUD TYPES

CUMULUS

Cu

Cumulus clouds are easy to recognise. They are the fluffy clouds that float across the sky on a fine day, and are often known as ‘fair-weather clouds’. The individual heaps of cloud are generally well separated from one another – at least in their early stages. They have rounded tops and flat, darker bases. It is normally possible to see that these bases are all at one level. Together with stratus and stratocumulus, they form closer to the ground than other cloud types.

The colour of cumulus clouds, like that of most other clouds, depends on where they are relative to the Sun and the observer. When illuminated by full sunlight they are white – often blindingly white – but when seen against the Sun, unless they are very thin, they are various shades of grey. This should be borne in mind when reading the descriptions.

Cumulus clouds are the visible sign of bubbles of warm air (thermals) rising from the ground when it is heated by the Sun. Individual thermals generally last for a few minutes and then decay. You can see this process at work if you watch what happens to an individual cloud. Isolated cumulus fade away as the moist air forming them gradually mixes with the drier air from their surroundings.

Early in the day cumulus are often like small wisps of cotton wool. As heating increases more thermals arise, which produce larger clouds. These also decay, and may become very ragged in shape rather than rounded heaps if there is a stiff wind blowing. All the thermals (and ordinary small cumulus) die away towards dusk.

Frequently, many active cells occur close together and combine to give a cloud that covers a larger area or is much deeper (or both). Deep cumulus often lean downwind, because the wind speed is usually greater at higher altitudes. Sometimes, however, high vertical towers may build up. When heating is particularly vigorous, cumulus may evolve into much heavier cumulus (cumulus congestus) that may even produce some rain, or turn into cumulonimbus clouds.

See also the following species of cumulus:

STRATUS

St

Stratus is a low, grey, water-droplet cloud that may hide the top of high buildings. It often has a fairly ragged base and top, and is identical to fog, which is stratus at ground level. Although the cloud may be so thin that the outline of the Sun is seen clearly, generally there are no optical phenomena. It forms under stable conditions and is one cloud type associated with ‘anticyclonic gloom’.

Stratus forms either by the slow uplift of moist air, or when a gentle wind carries nearly saturated air across a cold land or sea surface. It tends to arise when wind speeds are low, because strong winds mix a deep layer of air, which normally prevents the cloud from forming. However, stratus may occur, even with strong winds, when there is a large temperature difference between the air and the surface. Stratus also often forms when a moist air stream brings a thaw to ground that is covered in