Heat and moisture are both necessary for tornadoes, which helps explain why they seem to hit the South Coast most frequently.

But why so many should strike a few districts of Sussex is not clear.

A Meteorological Office spokesman said part of the explanation could be that tornadoes which hit densely populated area are more likely to reported.

Bognor was struck by a 120mph tornado on Saturday and nearby Selsey found itself in the path of a 90mph twister this morning.

Today the Tornado and Storm Research Organisation (Torro) said it received unconfirmed reports of more tornadoes in Hampshire and on the Isle of Wight.

Dr Terence Meaden, from Torro, said: "The air is potentially ready for tornadoes a lot of the time. They are almost there, but not quite happening.

"There has to be an extra factor that is the trigger, and this seems to be maritime humidity, the humid air you get along the South Coast.

"Tornadoes typically start out at sea, hit the coast and run in for about a mile, damaging buildings."

But this does not explain why there should be more tornadoes in Sussex than in Cornwall, for example.

The Met Office spokesman said: "Tornadoes are associated with thunderstorm activity, and for that you need a lot of moisture and a lot of heat, so it's not surprising that they should be more common in the South."

But he added: "Getting eyewitness accounts is often a problem with tornadoes. They are more likely to be reported in places where they are easily noticed."