How hurricanes affect Alabama

How hurricanes affect Alabama
U.S. Geological Survey (USGS) researcher Dave Thompson stands next to a garage in Gulf Shores, Alabama, that filled with sand after Hurricane Ivan in 2004. (contributed)

This is Hurricane Preparedness Week (May 3-9) in anticipation of the Atlantic Hurricane Season (June 1-November 30).

The threats from hurricanes to you and your family can vary widely depending on where you live.

Storm surge

Along the coast, storm surge is often the greatest threat to life and property from a hurricane. Storm surge is produced by water being pushed toward the shore by the force of the winds moving cyclonically around the storm.

In the past, large death tolls have resulted from the rise of the ocean associated with many of the major hurricanes that have made landfall. Hurricane Katrina (2005) is a prime example of the damage and devastation that can be caused by surge. At least 1,500 persons lost their lives during Katrina, and many of those deaths occurred directly, or indirectly, as a result of storm surge.

In 2004, Hurricane Ivan caused a storm surge as high as 13 feet.

Storm surge should not be confused with storm tide, which is defined as the water level rise due to the combination of storm surge and the astronomical tide. This rise in water level can cause extreme flooding in coastal areas, particularly when storm surge coincides with normal high tide.

Things to know about hurricanes from Alabama NewsCenter on Vimeo.

Learn more about storm surge at nhc.noaa.gov/surge.

Inland flooding

Hurricanes and tropical storms can cause flooding in every county of Alabama.

Tropical hurricanes often produce widespread, torrential rains in excess of 6 inches, which may result in deadly and destructive floods. Flash flooding, defined as a rapid rise in water levels, can occur due to intense rainfall. Longer-term flooding on rivers and streams can persist for several days after the storm.

Rainfall amounts are not directly related to the strength of tropical cyclones 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. In addition, mountainous terrain enhances rainfall from a tropical hurricane.

When approaching water on a roadway, always remember Turn Around Don’t Drown. Learn more at nhc.noaa.gov/prepare/hazards.php#rain.

Tornadoes and damaging wind

The wind from a hurricane can cause tornadoes and damaging wind gusts across all of Alabama.

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. In 2004, Hurricane Charley made landfall at Punta Gorda on the southwest Florida coast and produced major damage well inland across central Florida with gusts of more than 100 mph.

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

Tropical storm winds, 39 mph or more, are strong enough to be dangerous to those caught in them. For this reason, emergency managers recommend completing evacuations before the onset of tropical storm-force winds, not hurricane-force winds.

Learn more about all of the hazards associated with hurricanes at nhc.noaa.gov/prepare/hazards.php.

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