A cumulonimbus capillatus cloud is massive in every measure. It's the only cloud which can extend from almost ground level up to the tropopause. This is the tropical monster giving monsoon rains, rain showers, hail and wind. The vertical movements inside and around this cloud can be a hazard for aviation. The top of the cloud extends horizontally on high altitudes, seen here.

Another example of the massive horizontal extension on high altitudes, here at around 10000 - 12000 metres.

School book example of the formation.

This beautiful formation was formed just before sunset at high altitude. The horizontal extension is maybe at its beginning, and you can visualise the coming development.

After long and hot days with extreme temperatures (30 degrees Celsius and more), very often capillatus clouds are formed in the evening. These are often welcome, giving winds and rain to the thirsty ground and people. Perfect solution by nature, isn't it? Extreme heat produces drought and thirst, but as well rain!

Two massive formations with very clear horizontal extensions in all directions.

Navigating around these big fellows can take you quite close sometimes. Here the top and horizontal extension is unusually clear in contrast. This particular cloud is part of an ITF, Inter Tropical Front, see further below.

The same cloud as above forming the ITF, Inter Tropical Front. This front system is formed in the tropics and follows the sun's movement in the sky. The front wanders north to south and back to the north throughout the year giving the rainy seasons in the affected region. This particular front extends to more than 15000 metres altitude. Note the normal cumulus clouds in front of the front.

Sometimes the cumulonimbus clouds are hidden in other cloud formations, normally a front system filling the sky with other clouds. Here the top of a cumulonimbus is seen coming through a covered sky. The term isolated embedded is then used.

Can you see the tops reaching above the the otherwise covered sky? At times like these a weather radar is essential for planes flying through.

So what does it look like staying on ground? Well, it could be mistaken as many other cloud types being grey and covering the sky. These two pics from the bush in Ghana are typical for the formation, however. And as so often giving rain now and then.

Just another grey underside? Well, it's a capillatus.