How tornadoes can spawn from tropical systems

A Moment of Science

While wind, rain, and storm surge are the major threats of a tropical system, tornadoes are a real threat- even hundreds of miles away.

In general, tornadoes are rare in the Lowcountry. But a good chunk of few tornadoes we do see don’t occur in spring, but late summer and autumn as hurricanes and tropical storms move onto land.

We see this time and time again with tropical systems. In fact, it’s rare for a hurricane to not produce tornadoes after landfall. The majority of these don’t form in the eyewall, but in the intense outer bands that can extend over 200 miles away from the storm’s center, usually in the front right quadrant or to the northeast of the hurricane’s eye.

This “sweet spot” for tornado development comes down to spin, or shear. At the surface, we’re battered with strong southeast winds as the storm’s bands circulate counterclockwise. But higher up in the atmosphere, the wind comes from the nearly opposite direction! This vertical wind shear only increases after landfall as winds at the surface slow down due to friction over land, increasing that tornado threat.

Spin ups can happen quickly, so be alert and ready to move to your established “safe place,” preferably an interior room on the first floor of your home without any windows or outside facing doors. 

Thankfully, these tornadoes are short-lived and generally weak compared to springtime supercells like the Lowcountry experienced last spring.

While tornadoes pose a much more isolated risk compared to wind, rain, and storm surge in tropical systems, they’re still worth planning for. Especially for tropical systems that crash into the Florida panhandle and move north, placing us in the front right quadrant.

This pattern with Irma in 2017 produced 4 tornadoes in the Charleston metro and 13 with Frances in 2004, both of which were tropical storms by the time they reached us.

This goes to show that you should be prepared for any system, even tropical storms!

Storm Team 2 Meteorologist David Dickson

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