A hurricane's deadly forces
Hurricanes have an arsenal of effects that can destroy property and cause loss of life. The combination of wind and water can have devastating impacts on man and nature. Learn what these deadly features can do and how to survive them.
Storm Tides and Waves
Storm surge is simply the rise in water that floods the coast as water is pushed onshore by strong winds, and to a much lesser degree very low pressure. It is important to know the tides of the coastal area where you are located. For example, many locations on the Gulf coast have very small tidal ranges, whereas locations on the U.S. east coast have large tidal ranges. It makes a significant difference on the impacts to the coast if a hurricane moves ashore during a low or high tide in a location where the tidal range is large.
Today, inland flooding causes the largest loss of life. In the past, when hurricane forecasting technology was not as sophisticated, storm surge was the reason for most deaths.
It is best to leave a structure that could be affected by the storm tide of a hurricane. The force from sea water is extremely powerful and can destroy a house easily. High waves carry the debris from destroyed buildings that are on the coast that batter other structures farther inland. Houses built on stilts have a much greater survivability from surge damage. Even so, it is best
not to "ride out" a hurricane and evacuate to a safer location.
Hurricanes produce strong sustained winds which have the capability of destroying structures and toppling trees and power lines. The Saffir-Simpson hurricane scale gives an estimate on the type of wind damage that can be expected with different categories of hurricanes. A major hurricane is considered a category 3 or higher. Maximum sustained winds are greater than or equal to 111 mph.
Strong winds can blow in garage doors, break windows, or lift roofs off of houses. Make sure that you have shutters or plywood to cover windows properly during a hurricane. Also, know how structurally sound your roof and garage doors are so that they will not fail in the event of high winds.
The safest place to stay is in the basement to protect you and your family from high winds. If you are in a flood zone, evacuate to higher ground. If you do not have a basement, find a small room on the lowest floor with no windows near the center of the house to stay.
Tornadoes are many times associated with land falling tropical cyclones. The tornadoes usually occur in outer rain bands in the right
front quadrant with respect to storm motion. Most of the tornadoes occur within 24 hours of land fall, although it's possible for tornadoes to still occur two or three days later still associated with the circulation.
The largest hurricane associated tornado outbreak on record occurred with Hurricane Ivan in 2004 with 117 tornadoes. Other hurricanes that produced a significant tornado outbreak were: Hurricane Beulah (1967) - 115, Hurricane Frances (2004) - 103, and Hurricane Rita (2005) - 98 tornadoes.
Unlike their Midwest cousins, tornadoes on average are weaker in hurricanes. There is usually a weaker signature on radar and hail almost never accompanies them. Stronger land falling hurricanes have a greater potential to produce tornadoes than weaker ones.
Tornadoes occur with land falling hurricanes as the hurricane moves over land and encounters greater low level friction from the land. This slows the wind at the surface more than higher aloft, adding to vertical wind shear. It is this increase in wind shear that sets up an environment favorable for tornado development.
Follow the same safety guidelines for high winds to protect you and your family from the harmful effects of tornadoes.
All hurricanes do not produce severe flooding. There are several factors that contribute to the flooding potential of a hurricane or weaker tropical cyclone. The most important factor is the rate of motion. If a tropical cyclone moves into a region where steering currents from the winds aloft are weak, very heavy rain can result. It is possible for the tropical cyclone to be nearly stationary for days resulting in very heavy rainfall amounts of 40 to 50 inches or more. Recently, Hurricane Harvey dropped rainfall totaling to 50 inches near Houston, Texas causing catastrophic flooding.
The surrounding environment where the hurricane forms is another consideration. If a hurricane forms in the deep tropics, it usually can tap a deeper source of deep layered moisture. Hurricanes that form in higher latitudes have a greater chance of entraining dry air from mid latitude weather systems limiting moisture. Rainfall amounts are also affected by the terrain of a location. Mountains cause an added lift to occur, enhancing rainfall rates on the windward slopes.
When a tropical cyclone is approaching, understand the potential for heavy rainfall to produce flooding or flash flooding
where you live. If you live in a flood plain, evacuate to high ground before the hurricane's effects arrive.
A hurricane has the potential to cause widespread damage and loss of life. The best way to survive the effects of a hurricane is by staying informed. For more on how to prepare before a hurricane strikes, check Tropicalweather.net's article on hurricane preparedness.
Explore more hurricane impacts with the Saffir-Simpson wind scale.
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