WRAL WeatherCenter Blog

Tropical Tornadoes

Posted May 25, 2010

It is that time of year again; hurricane season is right around the corner. With the season commencing on June 1st and retiring on November 30th, we will have plenty time to tangle with these tropical systems.

North Carolina has a rich history dealing with hurricanes and their impacts. Hazel, Bonnie, Bertha, Fran and Floyd are names locals know well. For many newcomers, hurricanes have been seemingly absent from our coastline. The last hurricane to have a major impact on the state was Isabel in 2003. Our state is overdue for a landfalling hurricane. Could this be the year we are impacted? Only time will tell.

Tornadoes: An Embedded Threat

Tornadoes from hurricanes are probably not something many folks think of, but tornadoes are typically the first threat we will face from a tropical system as the outer bands or squall lines push inland — sometimes over a hundred miles ahead of the hurricanes eye. In 2004, a record year for tornadoes in North Carolina, around 45 tornadoes touched down statewide mostly spawned by the remnants of hurricanes Bonnie, Charley, Gaston, Frances and Ivan.  All of these storms came from the southwest and were not traditional landfalling storms for North Carolina.

Tornadoes can also form after a hurricane makes landfall. Once a hurricane makes landfall, the storm often weakens — slowing down winds near the surface while the winds near the top keep their momentum. It takes strong shifting winds at low levels, the lowest 3,000 feet or so, to be the source for these hurricane-related tornadoes. Most tornadoes from tropical systems form north and east of the center of circulation. This region of the storm has the most shear and most favorable wind profiles necessary for tornado development.

Often these tropical tornadoes are weak and short-lived, but they still are strong enough to demolish mobile homes, severely damage well built homes, and flip vehicles overs. These quick-developing tornadoes keep meteorologists on their toes as they diligently scan the radar to find any circulation that may become tornadic. These tornadoes may also come without warning and dissolve before a warning is even issued. Researchers often don't realize a tornado has formed until they survey the hurricane's damage and recognize the tell-tale signs of a tornado. According to one researcher, "a hurricane, if you go look at the damage, is just a big area where there's relatively uniform damage. When a tornado strikes, you get very intense, very narrow lines of damage."

Tornadoes are just one aspect of a tropical system….also threatening are flooding, storm surge and of course the winds from the storm!


 

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