The Weather Hazards Associated With Hurricanes

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. Because of its ability to travel across ocean and land, a hurricane is almost impossible to outrun.

In addition to having an evacuation plan in place, your best line of defense against hurricanes is to know and 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 can extend 25-150 miles (40-241 km) from the storm center. Sustained winds pack enough force to cause structural damage and carry loose debris. 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.

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 moving slowly. This water overwhelms rivers and low-lying areas. When rainbands release water for several consecutive hours or days, this leads to flash and urban flooding. 

Because tropical cyclones of all intensities (not just hurricanes) can produce excessive rains, 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 by 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 risk of related hazards, especially storm surge and tornadoes.

A direct hit from the right-front quadrant of a hurricane (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 has sustained winds of 90 mph (category 1 strength) and is 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 with 25 mph steering winds becomes 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 is traveling due west, the right front quadrant would actually be its northern region.