A tropical cyclone is a large storm rotating around an area of very low pressure, with strong winds blowing around the centre. The whole storm system may be five to six miles high and 300 to 400 miles wide, although sometimes can be even bigger. It moves forward like an immense spinning top, at speeds of up to 30 m.p.h. At its very early and weak stages it is called a Tropical Depression. When the winds reach 39 m.p.h. it is called a Tropical Storm. If the wind should reach 74 m.p.h. or more the tropical storm is called a Hurricane in the Atlantic and the north-east Pacific or a Typhoon in the north-west Pacific. In other parts of the world, such as the Indian Ocean and South Pacific the term Cyclone or Tropical Cyclone is used.

America has the most sophisticated tropical cyclone warning system. Once a tropical depression has been identified, a series of forecast advisories, which detail the expected track and likely strength of the tropical cyclone, is broadcast. When there are definite indications that a tropical cyclone is approaching land, watches and warnings along coastal regions are raised, which aim to give information to the local authorities of places likely to be in the tropical cyclone’s path, so that they can make preparations to protect public safety.

Specially designed shelters in which people can ride out the worst of the weather may have been built in advance. Coastal regions immediately in a tropical cyclone’s path are particularly dangerous and people are usually advised to move away from these. In the USA, this can involve the mass evacuation of a million or more people. Warnings are broadcast on TV and radio. NOAA Weather radio is available on a variety of frequencies and gives up-to-date information and advice. There is also a lot of information on a variety of web sites, the most authoritative being those maintained by NOAA and the National Hurricane Center.