On Thursday, with Hurricane Helene approaching the U.S. coastline, tornado watches were issued for over 25 million individuals.

Although tornadoes often don’t receive as much media attention as the fierce winds and dangerous storm surges of hurricanes, they remain a significant threat when storms make landfall and move inland.

This danger is heightened as tornadoes can form over 1,000 miles from where a hurricane makes landfall, and even outside the storm’s direct path, noted Roger Edwards, a tornado specialist at the Storm Prediction Center.

As Helene advanced inland, the center had already begun to warn of an elevated tornado risk early in the week. Edwards highlighted that the extensive size of Helene amplifies the potential for tornadoes, raising concerns for individuals residing far from the initial landfall on the coast.

By Thursday afternoon, tornado watches were issued for states including Florida, Georgia, and South Carolina.

Tornadoes originating from hurricanes can develop rapidly and often be hidden by heavy rain, making them difficult to spot, according to Edwards.

“People need to act immediately if a tornado warning is issued,” he cautioned. “Waiting to check outside can be dangerous, as a tornado could already be causing damage by the time they look.”

Residents in structures that might not endure a tornado are advised to utilize the forecasts provided by the center to develop relocation plans to safer locations, such as staying with family or friends, Edwards said. “Once a tornado watch is announced, it’s time to move to safety.”

Hurricanes Can Spawn Tornadoes for Several Days

“A hurricane can generate tornadoes for two to three days after moving inland,” Edwards explained. The most significant tornado risk linked to a hurricane was observed three days after Hurricane Ivan struck Alabama in September 2004.

Forecasters predicted numerous supercells would develop in regions such as Virginia, Maryland, and southern Pennsylvania.

“We were highly confident that we would see destabilization in the area, despite some weakening winds and persistent shear,” he noted. “And that’s exactly what unfolded—a highly productive tornado day.”

He emphasized that even far inland, people should stay vigilant if they are in the path of a hurricane’s remnants.

Examining Hurricane Beryl’s Tornado Record

Hurricane Beryl exemplified the significant number of tornadoes that can form as a hurricane moves inland, and how widespread they can become, Edwards pointed out.

Beryl made landfall on Texas’s Gulf Coast in July, yet its winds triggered so many tornadoes that it achieved a record 67 tornado warnings in one day from the National Weather Service in Shreveport, Louisiana. Remarkably, it also set a record for the Buffalo, New York weather service—over 1,300 miles away—with tornado warnings issued there as well, totaling more than 100 linked to Beryl’s winds.

The National Weather Service is still analyzing storm data post-Beryl. By the time all assessments are complete, Edwards anticipates Beryl caused about 65 tornadoes.

“This total would likely place Beryl in the top five for tornado production,” he stated.

Beryl exhibited more instability and wind shear than many other hurricanes during their inland phase, Edwards noted, adding that greater wind shear from weakening hurricanes correlates to a higher number of tornadoes.

The Impact of Hurricane Size on Tornado Generation

Similar to Beryl, Helene also appears poised to produce many tornadoes, Edwards remarked. “In terms of tornado generation, the size of a hurricane is crucial.”

Larger storms generally create broader areas of beneficial winds and instability, increasing the odds of tornado formation, he clarified.

Helene is particularly large, with an average diameter exceeding 440 miles, according to data from the National Hurricane Center, in comparison to the typical hurricane diameter of about 300 miles.

As Helene intensifies while approaching the coast, it may enhance the likelihood of tornadoes due to increased wind shear production, Edwards explained.

Some of the most prolific tornado-producing hurricanes in history included the largest storms like Ivan in 2004, Beulah in 1967, and Harvey in 2017.

Using Tornado Data for Future Preparedness

The National Oceanic and Atmospheric Administration has gathered data on tornado occurrences for many years, but the most reliable data has been collected since the introduction of Doppler radar. Consequently, the database that Edwards uses starts from 1995.

Most tornadoes occur in the eastern part of a hurricane because forming a tornado requires conditions like moisture, instability, and lift, which are typically present on the “right” side of the storm, according to Edwards.

He noted that tornadoes tend to form most frequently in the Northeast section of a storm. While tornadoes can also appear in the Southeast section, these areas usually remain over water for longer periods, meaning it’s likely that tornadoes are forming as vortexes out in the ocean. “We simply cannot track their movements unless they transition to land,” he added.

Data from Iowa State University has shown that Hurricane Beryl resulted in a significant 113 tornado warnings, as previously reported by YSL News in July.

“Having 113 warnings is quite substantial, especially since this occurred in July, making it even more noteworthy,” explained Daryl E. Herzmann, a systems analyst at Iowa State University who conducted the research. He added, “The right-front quadrant of the hurricane was in an unusually conducive environment for tornado formation.”

Since 1995, hurricanes and tropical storms have caused over 1,700 tornadoes, stated Edwards.

Tornadoes From Hurricanes and Tropical Storms Since 1995