The Threat of a Hurricane - Are You At Risk?

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The Threat of a Hurricane - Are You At Risk?

For sustained violence, no form of weather beats a major hurricane. With wind speeds which may exceed 155mph (240 kph), torrential rain, destructive waves and storm surges which can raise sea level by 20 feet or more, their power is enormous, and they should never be taken lightly.

North America can claim to be the hurricane centre of the world. Every year hurricanes develop in the South Atlantic and make their way through the Caribbean, usually growing as they move westwards.

They start off as small disturbances with moderate winds and thunderstorms. Those that keep growing and develop a spiral wind pattern are classified as Tropical Storms and given a name. They will keep this name whether or not they intensify into a hurricane, for as long as they remain a threatening weather system.

As Caribbean islands are battered, the mainland of North America holds its collective breath. Will the hurricane reach the Gulf of Mexico, swing further north to cross the Atlantic Coast of the USA, or take a northward track and stay at sea? Will it be a relatively minor Category 1 hurricane, or will it grow to a devastating Category 5, like Camille in 1969.

But no matter how they are classified, all hurricanes are a threat to life and property. Each hurricane is different, although all are notable for strong winds and heavy rains. More information can be found at

Hurricanes can cause problems in five ways;

  • Strong Winds. Sustained wind speed is one of the main ways of classifying hurricanes. Category 1 hurricanes bring winds of 74-95 mph (119-153kph), Category 3, classified as a major hurricane, blows at 111-130mph (178-209kph), and the winds of Category 5 monsters exceed a devastating 155mph (249 kph). At these speeds many roofs and some complete buildings will be destroyed.

  • Storm Surge. Storm surge is mostly caused by strong winds driving sea water ahead of them, resulting in an increase in sea level. Because winds rotate anticlockwise around hurricanes, storm surges are highest within and to the left of its eye as viewed from landfall. Becasue they are wind related, they show a steady increase in height from low to high category hurricanes, from 3-5 feet in Category 1, through 9-12 feet in Category 3 to surges in excess of 18 feet (5.5m) in a Category 5 hurricane.

  • Strong Waves. On top of the storm surge come strong destructive waves. They are more notable for their speed and roughness than their size, because the high winds tend to blow the tops off them, but they are capable of significant damage in exposed situations.

  • Flooding Rains. Hurricanes are composed of thick bands of turbulent, rain laden clouds. Thunder and lightning are common, but the main result is long periods of torrential rain, inevitably leading to flooding, particularly when combined with storm surge.

  • Thunderstorms, including tornadoes. Although thunder and lightning are commonly seen with hurricanes, most destruction comes from the hurricane winds. But as the hurricane moves inland, it loses power and becomes disorganized. At this stage, when the atmosphere is still unstable, powerful storm cells may form, bringing violent winds, heavy rain, and often tornadoes to more inland areas.

This means is that the coastal fringe will be most affected by a hurricane, with the degree and area of severe damage increasing with increasing severity of the storm, particularly from Category 3 upward. Evacuation may be ordered as Category 3 or higher hurricanes approach, although mobile homes are in danger even in Category 2 hurricanes.

In a Category 3 storm, low lying areas within a few blocks of the shoreline will probably be evacuated, increasing to 5-10 miles (8-16km) for a Category 5 hurricane. As the severity of the hurricane increases, so does the extent of damage by both wind and storm surge, including the damaging effect of floating debris.

Low lying areas may be flooded, and roads cut, 3-5 hours before the arrival of the center of the hurricane, so although there is considerable warning of a hurricane's approach, the time available for safe evacuation is quickly reduced.

I am sure anyone who has experienced a hurricane is keenly aware of its power, and the speed with which conditions can deteriorate. But its affect on you can be greatly reduced with a little careful planning before the hurricane season, as well as well thought out action in the brief period of time between a hurricane warning and the start of disruption to access routes and damage to property.

That is the subject of Part 2 of this article

================================================================©2005, Graham McClung. A retired geologist, Graham McClung has had a lifelong interest in the outdoors. And where there's outdoors there's weather. He is the editor of where you can find reviews and advice to help you choose and use your own home weather station. You can email him at

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Last update 05/24/2011