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Thursday, Mar 23, 2017
Hurricane Guide

Hurricane dangers: More than wind and water

When most people think about the dangers associated with a hurricane, they think of two things – wind and water.

That might be correct, but oversimplifies the power of even a small hurricane.

The major hazards associated with hurricanes are:

♦  storm surge and storm tide

♦  heavy rainfall and inland flooding

♦  high winds

♦  rip currents

♦  tornadoes

♦ Storm Surge and Storm Tide

Storm surge and large waves produced by hurricanes pose the greatest threat to life and property along the coast.

A storm surge is an abnormal rise of water generated by a storm’s winds. Storm surge can reach heights well over 20 feet and can span hundreds of miles of coastline.

Conversely, storm tide is the level to which the water rises during a storm due to the combination of storm surge and the astronomical tide.

The destructive power of storm surge and large battering waves can result in loss of life, buildings destroyed, beach and dune erosion and road and bridge damage along the coast. Storm surge can travel several miles inland. Additionally, it can cause salt water intrusion to area water supplies, endangering the public health and the environment.

♦ Heavy rainfall and inland flooding

Hurricanes and tropical storms often produce widespread, torrential rains in excess of 6 inches, which may result in deadly and destructive floods. In fact, flooding is the major threat for people living inland. Flash flooding – a rapid rise in water levels – can occur quickly due to intense rainfall. Longer term flooding on rivers and streams can persist for several days after the storm. When approaching water on a roadway, always remember: Turn Around, Don’t Drown.

Rainfall amounts are not directly related to the strength of the storm itself but rather to the speed and size of the storm, as well as the geography of the area. Slower moving and larger storms produce more rainfall.

Tropical storm-force winds are strong enough to be dangerous to those caught in them. For this reason, emergency managers plan on having their evacuations complete and their personnel sheltered before the onset of tropical storm-force winds, not hurricane-force winds.

Hurricane force winds, 74 mph or more, can destroy buildings and mobile homes. Debris, such as signs, roofing material, siding and small items left outside become flying missiles during hurricanes. Winds can stay above hurricane strength well inland.

♦ Rip currents

The strong winds can cause dangerous waves that pose a significant hazard to mariners and coastal residents and visitors. When the waves break along the coast, they can produce deadly rip currents - even at large distances from the storm.

Rip currents are channeled currents of water flowing away from shore, usually extending past the line of breaking waves, that can pull even the strongest swimmers away from shore.

Hurricanes and tropical storms can also produce tornadoes. These tornadoes most often occur in thunderstorms embedded in rain bands well away from the center of the hurricane; however, they can also occur near the eyewall. Usually, tornadoes produced by tropical cyclones are relatively weak and short-lived, but they still pose a significant threat.