June 1, 2005 — Tornadoes can form when hurricanes make landfall, as their winds at ground level slow down, while the winds near the top keep their momentum. Data from 2004 show this tendency seems to have increased. Residents of hurricane-stricken areas should prepare for the eventuality of tornadoes.
Hurricane season officially started in June, and now forecasters say once a hurricane reaches land, it could form tornadoes -- thousands of miles away.
"This is where I felt the floor shudder," Tena Selby says. Selby's floor wasn't shaking from an earthquake. It was a tornado ripping through her backyard. "When I peaked around the corner and looked outside, I didn't see any grass," she says. "All I saw was debris, limbs, and the trees had fallen out back."
Spiraling tornadoes are usually caused by violent thunderstorms. But now meteorologists say another kind of weather system can stir up tornadoes...
"These are tornadoes that get their strength and power from the hurricane in which they're embedded," says Joe Schaefer, a meteorologist at NOAA Storm Prediction Center in Norman, Okla.
Once a hurricane makes landfall, the storm often weakens -- slowing down winds near the surface, while the winds near the top keep their momentum. This can lead to tornadoes, even thousands of miles away.
Meteorologist Greg Forbes, a severe weather expert at The Weather Channel in Marietta, Ga., says, "It takes real strong shifting winds at low levels, the lowest 3,000 feet or so, to be the source for these hurricane-related tornadoes."
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.
"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," Schaefer says.
Spotting tornadoes from hurricanes could keep forecasters busy this season. Selby feels fortunate she survived her close encounter. "It didn't hurt any of the houses in the neighborhood," she says. "We were so fortunate."
The year 2004 brought the most tornadoes on record with 1,817, and more than 330 of those were from hurricanes. Hurricane Ivan produced the most tornadoes ever in September 2004 with 123 spawned tornadoes.
BACKGROUND: Scientists have discovered that hurricanes can actually encourage the formation of tornadoes. When meteorologists studied hurricane-related damage, they found some damage that didn't fit the pattern, and discovered it was actually damage resulting from hurricane-related tornadoes.