PLAYING THE ODDS.

HOW TO GAUGE A HURRICANE THREAT.

Most weather-related accidents occur when pilots don’t realize they are heading into danger or won’t admit to themselves they are flying into conditions that they and their airplane aren’t equipped to handle. This isn’t a problem with hurricanes. They are so fierce and hard to miss that any pilot who hadn’t heard the news that a hurricane is nearby would almost surely recognize the danger in plenty of time to avoid it.

Hurricanes are born over oceans with surface water warmer than about 80 degrees. They begin weakening when they move over cooler water or land, but can remain dangerous as they move far inland.

These storms need warm water because they consist of bands of showers and thunderstorms that spiral in toward the eye, at the storm’s center. The energy that powers thunderstorms, including those that make up hurricanes, comes from the latent heat released when the water vapor in humid air condenses to form clouds and raindrops. Unlike thunderstorms over land, the extremely humid air above a warm ocean offers a continuing supply of warm water vapor to feed a hurricane’s thunderstorms. The atmosphere above cool water or land generally doesn’t have enough water vapor to support a hurricane or tropical storm.

Hurricanes begin as tropical depressions with winds blowing slower than 39 mph around an area of low atmospheric pressure over a warm ocean. When the maximum sustained surface winds reach 39 mph, a depression becomes a tropical storm and hurricane forecasters give it a name from a predetermined list. If a tropical storm’s sustained winds top 74 mph, it becomes a hurricane.

Global-scale winds in the surrounding atmosphere, from the surface to higher than 30,000 feet—called steering currents—push tropical storms and hurricanes across the ocean and land until the storm dies. Tropical storms and hurricanes in the tropics or the subtropics move generally east to west or toward the northwest from roughly 10 to 20 mph, with the path often curving toward a more northerly course. When hurricanes move north of Cape Hatteras, North Carolina, they usually pick up forward speed.

A fully formed hurricane could be 300 miles across with a central eye usually from 20 to 40 miles in diameter. The nearly calm eye in the center is where winds are light and the sky can be clear. The storm’s strongest winds are in the ring of thunderstorms around the eye—called the eyewall. Rain bands spiral inward toward the eyewall.

Winds blowing into a Northern Hemisphere hurricane follow a counterclockwise path into the hurricane, with air rising in the thunderstorms that make up the spiral bands and the eyewall. This air follows a clockwise path as it flows out of the hurricane’s top.

If you own an airplane and live within 100 or so miles of the U.S. Gulf of Mexico or Atlantic Ocean, monitor reports from the National Hurricane Center during the hurricane season. From June 1 to November 30, think about what you would do if a hurricane threatens your area.

The closer you are to the coast, the more you should worry.

A hurricane’s winds usually begin losing speed soon after the storm hits land, but not always. On September 22, 1989, Hurricane Hugo came ashore at Isle of Palms, South Carolina, as a Category 4 hurricane with 140-mph winds. When Hugo’s eye crossed Charlotte, North Carolina, roughly 150 miles inland, it was still a Category 1 hurricane with 87-mph winds at the Charlotte airport. A NOAA report says Hugo’s winds “resulted in a nearly 50-mile-wide swath of downed trees and power lines in this portion of North Carolina. Pleasure boats on Lake Norman, north of Charlotte, were piled into a heap like toys.”

Consider whether a hangar that’s available to you is likely to stand up to a hurricane’s winds. A hangar that collapses could do more damage than an airplane tied down would sustain from flying debris. Your best choice might be to fly your airplane to an airport far enough inland to be safe. Your insurance policy may cover the costs of moving the airplane out of harm’s way.

And you need to worry about flooding as well as winds. When they move ashore, hurricanes bring storm surge—water that the wind pushes ashore. This can cause major flooding, not only along the coast but also on bays and rivers near an ocean. Hurricanes also move ashore with heavy rain that can cause floods far inland, especially in hills or mountains.

Before deciding to fly to an inland airport you should check to see whether it has a history of floods. You don’t want to return to the airport to find your airplane sitting in six feet of water. You will find links to information about storms with graphical and text discussions and forecasts on the Hurricane Center website (www.nhc.noaa.gov). One of the most useful set of products you’ll find on the NHC website are the forecast maps such as the one issued at 11 p.m. on October 26, 2012—three days before Hurricane Sandy came ashore just north of Atlantic City, New Jersey (below). The NHC produces updated forecasts, including maps, every six hours during a storm with more frequent updates as a storm nears land.

Using hurricane predictions is a matter of playing the odds. Even though forecasts have been getting better, you can’t count on any one being perfect.

If you decide to fly to safety, you need to realize that the hurricane might miss; damaging winds might not hit your airport. Look at it this way: You are playing the odds. You need to weigh the possible costs of not flying the airplane away with the potential costs of leaving it tied down at an airport a hurricane could hit.

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