Why do tropical cyclones increase the risk of hurricanes?

Tropical cyclones come with a few impacts – strong winds, heavy rains, and several coastal hazards being the most notable.

However, there is another danger that is sometimes overlooked, which is the increasing threat of tornadoes.

The twisted truth about hurricane-driven tropical cyclones

Hurricane-driven tropical cyclones are not unheard of. In fact, many tropical systems that make landfall produce it, or at least are at risk of producing it.

Once a storm moves over land, near-surface winds become obstructed by terrain and infrastructure, causing it to slow down while maintaining its speed above.

This change in wind speed and direction with height creates vertical wind shear, a key component necessary for tornado formation. Encountering a front or increase in atmospheric instability will increase the likelihood of this occurring.

Most of these tornadoes occur in the right front quadrant, or the “dirty side” of the storm, where winds are strongest. Although tornadoes are possible in any of the thunderstorms that make up the outer bands of the storm, they can occur even near the eyewall.

Hurricane Idalia in August 2023 produced historic impacts across parts of the Southeast, including tornadoes, tropical storm force winds, storm surge and record rainfall. It also caused several tornadoes as well.

The National Weather Service (NWS) confirmed 10 tornadoes as Idalia passed through the Southeast, many of which lasted only briefly.

Before that, there was good warning of the danger of tornadoes. Many areas with confirmed tornadoes were under a tornado watch early on.

Tropical cyclones generated by hurricanes are usually weak and short-lived.

According to the National Oceanic and Atmospheric Administration (NOAA), this is because much of the instability associated with tropical cyclones occurs in the lower levels of the atmosphere. As a result, thunderstorm cells capable of producing tornadoes are smaller and more shallow.

Most tornadoes produced by tropical systems are usually rated only EF-0 or EF-1, but stronger tornadoes are still possible.

In this image from video provided by Scott Smith, a fast-moving tornado produced by Ida’s remnants is seen in the distance before the toll booth of the Burlington-Bristol Bridge on Wednesday, September 1, 2021, in Burlington, New Jersey. (Scott Smith via AP)

In September 2021, Ida’s remnants spawned several hurricanes as they passed through the central Atlantic. Among the tornadoes reported, the NWS confirmed that an EF-3 tornado touched down in Mullica Hill, New Jersey, damaging several homes and property.

Most hurricane warning cells occur during the minutes leading up to the event, and this is especially true for hurricane-driven tropical cyclones. That’s why it’s essential to stay alert and always have a way to receive important alerts and notifications when there’s a tornado threat.

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