Huge waterspout looms over Cuban coastal city as it swirls above the sea in stunning footage 

What are they and why do they form?

Waterspouts are whirling columns of air and water mist.

They form when cumulus clouds grow rapidly. These clouds are detached, fluffy-looking and cauliflower-shaped.

Cumulus clouds develop due to convection. This is when hot air rises and cools to form water vapour, which then condenses to form clouds. 

They fall into two categories: ‘fair weather’ and ‘tornadic’ 

(1) Tornadic waterspouts 

These are tornadoes that form over water, or move from land to water, and develop downwards during thunderstorms.

They have the same characteristics as a land tornado and can be accompanied by high winds and seas, large hail and lightning.

(2) Fair weather waterspouts 

These usually form along the dark flat base of a line of developing cumulus clouds and develop upwards from the surface of water.

They are generally not associated with thunderstorms and form in light wind conditions so don’t move very much. 

The five stages of formation 

1. Dark spot: A light-coloured disk appears on the water’s surface surrounded by a larger darker area

2. Spiral pattern: A combination of light and dark patches on the water spiral out from the dark spot

3. Spray ring: A ring of sea spray appears around the dark spot

4. Mature vortex: The waterspout reaches maximum intensity, making a funnel shape which appears hollow. It can rise several hundred feet.

5. Decay: The funnel and spray vortex begin to dissipate as the inflow of warm air into the vortex weakens

Sources: Met Office / National Ocean Service / National Weather Service