Why Hurricanes Bring Tornadoes After They Make Landfall

Tornadoes start in the outer edges of hurricanes. Once a storm is over land, the increase in surface friction can lead to twisters.

As Hurricane Isaias worked its way through the Mid-Atlantic states Tuesday, its winds steadily diminishing, a new hazard arose: tornadoes.

It is not uncommon for hurricanes to spawn tornadoes, and they are similar to those that arise out of large thunderstorms in the Central Plains, said Jana Houser, an associate professor of meteorology at Ohio University.

When they form, tornadoes are created in the outer rain bands of hurricanes, Dr. Houser said, which contain convective cells — thunderstorms — of their own.

But as long as a hurricane is over water, tornadoes will not form, Dr. Houser said. That’s because the surface of the water is relatively smooth, and in the formation of tornadoes “the biggest culprit is surface friction,” she said.

But once the rain bands reach land, surface friction greatly increases. That slows the storm’s winds close to the ground.

“You suddenly create a situation where you have a change in wind speed and often direction” compared with winds higher aloft, Dr. Houser said. This is called wind shear, and it can induce a spinning movement in the air.

At first this creates a spinning cylinder of air that is parallel to the surface. But as with any thunderstorm, the convective cells in a hurricane create strong updrafts. These can tilt the spinning air upright; a tornado is born.

If the updraft is very strong, the spinning air will be packed tighter, with a smaller diameter. When this occurs the tornado can intensify, like a figure skater pulling her arms in to increase her rate of spin.

This can lead to a powerful, destructive tornado. “But typically they are not as long lived, and typically a little weaker, than those formed from supercells in the Central Plains,” she said. And the threat diminishes over time as the hurricane breaks up and weakens further.


This article was originally published on

Recent news

Sri Lanka returns 'hazardous waste' to UK

Sri Lanka says it is sending 21 containers of waste back to the UK after… Read more

A Moving Checklist for Organizing Your Next Move

Moving can be so stressful: the packing, finding moving boxes, hiring movers, or doing it… Read more

Touring Superleggera fires the shark-like Aero 3 onto road and track

"Weight is the enemy, air resistance the obstacle." Not novel ideas to anyone who's spent… Read more

We're Not Doing Nearly Enough To Stop The Planet's Spiraling Plastic Problem

The planet’s plastic problem is swirling out of control and current efforts to get out… Read more

Study tallies up the plastic fibers shed globally through laundry

Discarded soda bottles, cigarette butts and fishing nets are some common examples of pollution in… Read more

Company Uses Peas To Make Eco-Friendly Material That Acts Like Single-Use Plastic

Microplastics are a big polluter of our waterways and oceans, and single-use items are a… Read more

'Zombie' Tropical Storm Paulette returns from the dead because it's 2020

As if the weather chaos of a record hurricane season wasn't enough, we now have… Read more

We know climate change set the conditions for Oregon fires. Did it stoke the flames, too?

As the global ocean temperatures rise due to climate change, scientists from the University of… Read more

The disturbing truth about plastic recycling

Our oceans are now awash in at least 150 million tons of plastic, an amount… Read more

'Shocking': wilderness the size of Mexico lost worldwide in just 13 years, study finds

Researchers say loss of 1.9m square kilometres of intact ecosystems will have ‘profound implications’ for… Read more