Tropical cyclones are intense circular storms that originate over tropical oceans are called hurricanes in the Caribbean, North Atlantic, and eastern Pacific regions. They are most likely to form in late summer and early fall, when ocean temperatures exceed eighty degrees F. Tropical cyclones may develop tremendous strength and become most destructive of all storms. These storms always start over an ocean and usually move across areas of warm water, the source of energy. When they strike a large land area, they quickly weaken; the storm is cut off their source of energy and friction caused by land slows their winds. Tropical cyclones are characterized by very strong winds and torrential rains, severe thunder storms, and water spouts are embedded in the storms cloud system.
Tropical cyclone is a rotating pressure weather system that has thunderstorms but no fronts. Hurricanes originate in the Atlantic basin, which includes the Atlantic Ocean, the Caribbean Sea, Gulf of Mexico, the eastern north Pacific Ocean, and the less frequently, the central north Pacific Ocean. ''Hurricane Season'' begins on June 1 and ends on November 30, although hurricanes can, and have, occured outside of this frame. When a storm's maximum sustained winds reach seventy-four miles per hour, it is called a hurricane. The Saffir-Simpson Hurricane Wind Scale, is a one to five rating, or category, based on a hurricanes's sustained winds. The higher the category, the greater the potential for property damage.
Tropical cyclones are like giant engines that use warm water and moist air as fuel. That is why they only form only on warm ocean waters near the equator. Air from surrounding areas with high air pressure pushes into the low pressure area. Then that ''new'' air becomes warm and moist and rises too. As the warm air continues to rise, the surrounding air swirls in to take its place. As the warm air rises and cools off, the water in the air forms clouds. The whole system of clouds and winds spin and grow fed by the ocean's heat and water, evaporating from the surface. Storms that form north of the equator spin counterclockwise. Storms that form south of the equator spin clockwise.
Tropical cyclones derive their energy from the warm warm tropical oceans, and do not form unless the sea surface temperature is above twenty-six degrees C. The circular eye or the center of a tropical cyclone is an area characterized by light winds and often clear skies. Eye diameters are typically forty kilometers, but can range from under 10 kilometers to one hundred kilometers. The eye is surrounded by a dense ring of cloud about sixteen kilometers high, known as the eye wall, which marks the belt of strongest winds and heaviest rainfall. Cyclones have wind gusts in excess of ninety kilometers per hour around their centers, and most severe cyclones, gusts can exceed two-hundred-eighty kilometers per hour. These very destructive winds can cause extensive property damage, and turn airborne debris into potentially lethal missiles.
Tropical cyclones are essential features of the Earth's atmosphere, as they transfer heat and energy between the equator and the cooler regions near the poles. The whole storm system may be five to six miles high and three-hundred to four-hundred miles wide, although sometimes can be even bigger. It typically moves forwards at speeds of ten to fifteen miles per hour, but can travel as fast as forty miles per hour. At a tropical cyclone's very early week stages, it is called a tropical depression. When winds reach thirty-nine miles per hour, it is called a tropical storm. If the wind should reach seventy-four miles per hour, the tropical storm is called a hurricane in the Atlantic and the eastern north Pacific or a typhoon in the western north Pacific. Great amounts of energy are transferred when warm water is evaporated from tropical seas. This energy is stored within the water vapor contained in most air. As air ascends, ninety percent of the stored energy is released by condensation, giving rise to the towering cumulus clouds and rain.
The warm water is one of the most important keys as it is water that powers the tropical cyclone. As water vapor cools it rises. This cooling causes the water vapor to condense into a liquid we see as clouds. In this process condensation, heat is released. This heat warms the atmosphere making the air lighter still which then rises into the atmosphere. As it does more air moves in near the surface to take its place, which is the strong wind we feel from these storms. Just having warm water alone is not enough for the formation of a tropical cyclone.
The eye represents an area of the hurricane where there is little to no precipitation, the sun or stars can be visible for a time, and the winds are light. Also in the eye is the lowest barometric pressure associated with the hurricane. Air will rapidly in a counterclockwise fashion around the center of the hurricane. As air continues to rise rapidly causing the ongoing heavy convection on the eye wall, there is a pocket of air that sinks towards the water or ground. The sinking air that occurs inside the eye wall is when the eye of the hurricane will start to appear visible on sattelight imagery. The eye of a hurricane can last anywhere from a couple of hours to several days if the environment remains favorable.
When a hurricane makes landfall, the shear force of hurricane strength winds can destroy buildings, topple trees, bring down power lines, and blow vehicles off roads. When flying debris such as signs, roofing material, building siding, and small items, is added to the mix, the potential for building damage is even greater. Many people have been killed or seriously injured by falling trees and flying debris that fell from hurricanes. Hurricane winds impact homes and other buildings in two different ways: 1. differential pressures act on the building envelope. 2. wind borne debris may strike a building. Rain water damage to a building's interior will normally result after damage to the building envelope has occurred. Wind borne debris generated from loose-laid ground materials and/or building components can fly an unbelievable distance up to several hundred feet. Wind speed tends to decrease significantly within twelve hours. An often misunderstood aspect of hurricane winds is the potential for increased damage as wind speeds increase. The forces against structures do not increase linearly, they increase exponentially, and as wind speeds increase. Hurricane wind damage is also dependent on other factors such as the duration on high winds, change of wind direction, amount of accompanying rainfall, and condition of affected structures. Depending on circumstances, less intense storms may still be strong enough to produce significant damage, particularly in areas that have not sufficiently prepared in advanced of the storm.
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