Tropical Cyclones

A Tropical cyclone is an intense circular storm that originates over warm tropical oceans and is characterized by low atmospheric pressure, high winds, and heavy rain. In indian Oceans they are called cyclones, in the Caribbean they are hurricanes, and in the South China Sea they are called typhoons. Meteorologists name each tropical cyclone, in order to emit forecasts and warnings. The World Meteorological Organization (WMO) applies each new cyclone season alphabetically. This names can be reused in different seasons, but the ones from the most dangerous cyclones are retired. Hurricanes need a lot of heat to form and a sea surface temperature of at least 26°C, which is why they usually occur over tropical seas. They also need to be between 5 and 20° north or south of the equator. They form when:

1. Air above the surface is heated, and the warm moist air starts to rise.
2. A deep centre of low pressure develops, which sucks up even more air from the surface.
3. Wind speeds around the centre of the cyclone increase to 150-200 km per hour, in a huge circular swirl of cloud.
4. Torrential rain falls, except from the cyclone's eye (where the weather is calm and dry).

The intensity of a cyclone is determined by its wind speed. There are different intensity scales across the world. For example, in Australia a Category 1 cyclone is when the wind speed is less than 78 miles per hour; it is a Category 2 cyclone when the wind speed is between 78 and 102 miles per hour; in a Category 3 the wind speed is between 103 and 139 miles per hour; in a Category 4 cyclone it is between 140 and 173 miles per hour; and finally it is a Category 5 cyclone when the wind speed is more than 174 miles per hour.

The main effects of tropical cyclones are heavy rain, strong wind, big storms, and tornadoes. The destruction it causes depends on the cyclone´s intensity, size and location. On coastal areas one of the main effects of a cyclone is the change of landscape (as its winds move sand dunes, and cause extensive erosion). However, inland, by heavy rainfall, cyclones usually cause mudslides and landslides in mountainous areas. After the cyclone has passed, the damages continue; standing water can cause the spread of a disease, and people may not be able to use transportation or communication (as it may have been destroyed). Along the world, nearly 2.000.0000 people have died because of a tropical cyclone. But, despite of their devastating effects, tropical cyclones are also helpful, by bringing rain to dry areas and moving heat from the tropics. We can reduce its bad effects by doing the following things:

1. Remove dead branches and trees.
2. Cover windows with plywood.
3. Store:

• Water (1 gallon per person per day).
• A battery-powered radio, many flashlights, and batteries for them.
• A first-aid kit and copies of any medical prescriptions that you have.
• Cash (as credit cards may not be usable if the power is lost).
• 5 to 10 gallons of gasoline
• Important documents in a waterproof bag.

4. Remove any loose objects in your yard and store them indoors.
5. Shut off the home's natural gas supply.
6. Fill bathtubs with water and then shut off the water supply to your home.
7. Close all doors within the house.
8. If you are told to evacuate, do so, and remain in your evacuation point until your area is declared safe for re-entry.