tropical storm

Intense low pressure system which forms over the warm oceans of the world's tropical areas, occurring in late summer and early autumn. Warm, moist air rises in a spiral to form a storm that can measure several kilometres across. The weather conditions vary considerably throughout the duration of the storm. Coastal areas are usually the worst affected by tropical storms, which can bring about both human and financial damage. Areas affected by a tropical storm often lose their electricity, water, and sewerage facilities. Tropical storms in different parts of the world are known by various names: hurricane, tropical cyclone, or typhoon.

As a storm approaches, temperature and pressure both fall rapidly, whilst cloud cover and wind speed increase. Rainfall gradually increases until it is torrential, often with thunder and lightning. Wind speeds can reach up to 160 km/100 mi per hour. The passage of the calm ‘eye’ of the storm may take two or three hours. During this time, the skies clear and the temperature and pressure rise. Once the eye has passed the storm begins again with renewed force. This time the winds blow from the opposite direction. The whole storm moves at about 25 km/16 mi per hour and takes several hours finally to move away.