In meteorology, a cyclone is an area of closed, circular fluid motion rotating in the same direction as the Earth. This is usually characterized by inward spiraling winds that rotate counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere of the Earth. A "tropical cyclone" is a synonym for a hurricane.
Katrina was the largest hurricane of its strength to approach the United States in recorded history; its sheer size caused devastation over 100 miles (160 kilometers) from the storm's center.
A hurricane's eye ‑- the relatively calm center ‑- is usually 20 to 30 miles wide, and the rest of the storm can extend as many as 400 miles from it.
Researchers from MIT and Yale University have found that coastal regions of North America and the Caribbean, as well as East Asia, are most at risk for hurricane damage — a finding that may not surprise residents of such hurricane-prone communities. However, the researchers say by the year 2100, two factors could more than quadruple the economic damages caused by tropical storms in such regions and around the world: growing income and global warming.
Two hurricanes lashed Mexico in 1984 and caused considerable damage to several communities. However, the rains filled reservoirs, saved crops and the economic agricultural gains more than offset the coastal losses.
A new study suggests that tropical cyclones shoot water high into the atmosphere. The result may be a small but significant contribution to the greenhouse effect.
Sea temperatures of 27 degrees or above, along with a group of thunderstorms or pre-existing conditions, create ideal weather conditions for a cyclone to form. To give an example, Hurricane Katrina, which hit New Orleans in 2005, formed in sea temperatures around 32 degrees or warmer.
To make comparisons easier and to make the predicted hazards of approaching hurricanes clearer to emergency managers, National Oceanic and Atmospheric Administration's hurricane forecasters use a disaster-potential scale which assigns storms to five categories. This can be used to give an estimate of the potential property damage and flooding expected along the coast with a hurricane. The scale was formulated in 1969 by Herbert Saffir, a consulting engineer, and Dr. Bob Simpson, director of the National Hurricane Center.
The Saffir-Simpson Hurricane Scale is a rating system based on the hurricane's current intensity. Numbered 1 to 5 it is used to give an estimate of the potential property damage and flooding expected along the coast from a hurricane landfall. Wind speed is the determining factor in the scale, as storm surge values are highly dependent on the slope of the continental shelf in the landfall region.
Great amounts of energy are transferred when warm water is evaporated from tropical seas. This energy is stored within the water vapour contained in moist air. As this air ascends, 90% of the stored energy is released by condensation, giving rise to the towering cumulus clouds and rain. The release of heat energy warms the air locally, causing a further decrease in pressure aloft. Consequently, air rises faster to fill this area of low pressure, and more warm, moist air is drawn off the sea, feeding further energy to the system.
Tropical cyclones are intense, spinning storm systems, with low-pressure centres that can be vast in size. They form over warm oceans and can wreak havoc when they approach the shore. As the name suggests, tropical cyclones and hurricanes occur in the world's tropics. They require the difference in speed of rotation of the Earth at different latitudes to gather momentum as they spin, and they can form either side of the equator.