HurricanesHurricanes

Hurricanes

What is a Hurricane?

A hurricane is a type of tropical cyclone, the generic term for a low pressure system that generally forms in the tropics. A typical cyclone is accompanied by thunderstorms, and in the Northern Hemisphere, a counterclockwise circulation of winds near the earth’s surface.

The development of a hurricane begins with a depression or a low in the barometric pressure.  As the storm becomes more organized, classifications of the storm benchmark the development.  The following are the benchmarks for a developing storm.

Tropical Depression

An organized system of clouds and thunderstorms with a defined surface circulation and maximum sustained winds* of 38 mph (33 kt**) or less 

Tropical Storm

An organized system of strong thunderstorms with a defined surface circulation and maximum sustained winds of 39-73 mph (34-63 kt)

Hurricane

An intense tropical weather system of strong thunderstorms with a well-defined surface circulation and maximum sustained winds of 74 mph (64 kt) or higher

All Atlantic and Gulf of Mexico coastal areas are subject to hurricanes or tropical storms. Parts of the Southwest United States and the Pacific Coast experience heavy rains and floods each year from hurricanes spawned off Mexico. The Atlantic hurricane season lasts from June to November, with the peak season from mid-August to late October.

Hurricanes can cause catastrophic damage to coastlines and several hundred miles inland. Winds can exceed 155 miles per hour. Hurricanes and tropical storms can also spawn tornadoes and microbursts, create storm surges along the coast, and cause extensive damage from heavy rainfall.

Hurricanes are classified into five categories based on their wind speed, central pressure, and damage potential. Category Three and higher hurricanes are considered major hurricanes, though Categories One and Two are still extremely dangerous and warrant your full attention.

Category 1                   74-95 mph winds

Category 2                   96-110 mph winds

Category 3                   111-130 mph winds

Category 4                   131-155 mph winds

Category 5                   Greater that 155 mph winds

Flooding

Hurricanes can produce widespread torrential rains. Floods are the deadly and destructive result. Slow moving storms and tropical storms moving into mountainous regions tend to produce especially heavy rain. Excessive rain can trigger landslides or mud slides, especially in mountainous regions. Flash flooding can occur due to intense rainfall. Flooding on rivers and streams may persist for several days or more after the storm. Between 1970 and 1999, more people lost their lives from freshwater inland flooding associated with land falling tropical cyclones than from any other weather hazard related to tropical cyclones.

To prepare for a hurricane, you should take the following measures:

  • Make plans to secure your property. Permanent storm shutters offer the best protection for windows. A second option is to board up windows with 5/8” marine plywood, cut to fit and ready to install. Tape does not prevent windows from breaking.
  • Install straps or additional clips to securely fasten your roof to the frame structure. This will reduce roof damage.
  • Be sure trees and shrubs around your home are well trimmed.
  • Clear loose and clogged rain gutters and downspouts.
  • Determine how and where to secure your boat.
  • Consider building a safe room.

 

If a hurricane is likely in your area, you should:

  • Listen to the radio or TV for information.
  • Secure your home, close storm shutters, and secure outdoor objects or bring them indoors.
  • Turn off utilities if instructed to do so. Otherwise, turn the refrigerator thermostat to its coldest setting and keep its doors closed.
  • Turn off propane tanks.  Avoid using the phone, except for serious emergencies.
  • Moor your boat if time permits.
  • Ensure a supply of water for sanitary purposes such as cleaning and flushing toilets. Fill the bathtub and other large containers with water.

 

You should evacuate under the following conditions:

  • If you are directed by local authorities to do so. Be sure to follow their instructions.
  • If you live in a mobile home or temporary structure—such shelters are particularly hazardous during hurricanes no matter how well fastened to the ground.
  • If you live in a high-rise building—hurricane winds are stronger at higher elevations.
  • If you live on the coast, on a floodplain, near a river, or on an inland waterway.
  • If you feel you are in danger.

 

If you are unable to evacuate, go to your wind-safe room. If you do not have one, follow these guidelines:

  • Stay indoors during the hurricane and away from windows and glass doors.
  • Close all interior doors—secure and brace external doors.
  • Keep curtains and blinds closed. Do not be fooled if there is a lull; it could be the eye of the storm – winds will pick up again.
  • Take refuge in a small interior room, closet, or hallway on the lowest level.
  • Lie on the floor under a table or another sturdy object.

 

 http://www.nhc.noaa.gov/HAW2/english/basics.shtml

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