The Threat of a Hurricane - Are You At Risk?
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Handling a Hurricane, Part 1
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
- 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
- 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 http://www.home-weather-stations-guide.com where you can find reviews and advice to help you choose and use your own home weather station. You can email him at firstname.lastname@example.org================================================================
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Last update 05/24/2011