The Hazards of Hurricanes

Beware the High Winds, Storm Surge, Flooding, and Tornadoes

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Every year, from June 1 to November 30, the threat of a hurricane strike looms in the minds of vacationers and residents of U.S. coastlines. And it's no wonder why...with the ability to travel across ocean and land, a hurricane can't be outrun as can other severe storms.

In addition to having an evacuation plan in place, your best line of defense against hurricanes is to know and be able to recognize its main hazards, of which there are four: high winds, storm surge, inland flooding, and tornadoes.

High Winds

As pressure drops inside of a hurricane, air from the surrounding atmosphere rushes into the storm, generating one of its trademark characteristics--winds.

A hurricane's winds are among the first conditions to be felt during its approach. Tropical-storm-force winds can extend as far as 300 miles (483 km), and hurricane-force winds, 25-150 miles (40-241 km) from the storm center. Sustained winds pack enough force to cause structural damage and carry loose debris airborne. Remember that hidden within maximum sustained winds are isolated gusts that actually blow much faster than this.

Storm Surge

In addition to being a threat in and of itself, wind also contributes to another danger--storm surge.

See Also: What you need to know to understand the NHC's new storm surge warnings

While a hurricane is out to sea, its winds blow across the ocean surface, gradually pushing water out ahead of it.

(A hurricane’s low pressure assists in this.) By the time the storm nears the coast, water has “piled up” into a dome several hundred miles wide and 15 to 40 feet (4.5-12 m) high. This ocean swell then travels onshore, inundating the coast and eroding beaches. It is the primary cause of loss of life within a hurricane.

If a hurricane approaches during high tide, an already risen sea level will lend additional height to a storm surge. The resulting event is referred to as a storm tide.

Rip currents are another wind-induced marine hazard to watch for. As winds push water outward toward the shore, water is forced against and along the shoreline, creating a fast current. If there are channels or sandbars leading back out to sea, the current flows violently through these, whisking along anything in its path (including beachgoers and swimmers).

Rip currents can be recognized by the following signs:

  • A channel of churning, choppy water
  • An area with a noticeable difference in color when compared to the surrounding ocean
  • A line of foam or debris moving out to sea
  • A break in the incoming wave pattern

Inland Flooding

While storm surge is the main cause of coastal inundation, excessive rains are responsible for the flooding of inland areas. A hurricane's rainbands can dump up to several inches of rain per hour, especially if a storm is slow-moving. This much water overwhelms rivers and low-lying areas, and when experienced for several consecutive hours or days, leads to flash and urban flooding. 

Because tropical cyclones of all intensities (not just hurricanes) can produce excessive rains and carry this far inland, freshwater flooding is considered the most wide-reaching of all tropical cyclone related dangers.

Tornadoes

Embedded in a hurricane's rainbands are thunderstorms, some of which are strong enough to spawn tornadoes. Tornadoes produced by hurricanes are typically weaker (usually EF-0s and EF-1s) and shorter-lived than those occurring across the Central and Midwestern U.S.

As a precaution, a tornado watch is usually issued when a tropical cyclone is forecast to make landfall.

Beware the Right Front Quadrant!

A number of factors, including storm strength and track, influence damage levels caused from each of the above. But you may be surprised to learn that something as seemingly insignificant as which one of a hurricane's sides first makes landfall can also greatly increase (or lower) the damage risk, especially for storm surge and tornadoes.

A direct hit from the right-front quadrant (left-front in the Southern Hemisphere) is considered the most severe.

That's because it's here where the storm's winds blow in the same direction as the atmospheric steering wind, causing a net gain in wind speed. For example, if a hurricane had sustained winds of 90 mph (category 1 strength) and was moving at 25 mph, its right front region would effectively have winds up to category 3 strength (90 + 25 mph = 115 mph).

Conversely, because winds on the left side oppose steering winds, a reduction in speed is felt there. (Using the previous example, a 90 mph storm - 25 mph steering winds = a 65 mph effective wind).

Since hurricanes continually spiral counter-clockwise (clockwise in the Southern Hemisphere) as they travel, it can be difficult to distinguish one side of the storm from another. Here's a tip: pretend you're standing directly behind the storm with your back in the direction it's traveling; its right side will be the same as your right. (So if a storm was traveling due west, the right front quadrant would actually be its north region.)

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Means, Tiffany. "The Hazards of Hurricanes." ThoughtCo, May. 17, 2017, thoughtco.com/the-hazards-of-hurricanes-3443926. Means, Tiffany. (2017, May 17). The Hazards of Hurricanes. Retrieved from https://www.thoughtco.com/the-hazards-of-hurricanes-3443926 Means, Tiffany. "The Hazards of Hurricanes." ThoughtCo. https://www.thoughtco.com/the-hazards-of-hurricanes-3443926 (accessed November 24, 2017).