Landlocked Vermont might not be the first state that comes to mind for hurricanes, but the recent major storms made clear that it’s not immune from their havoc.
Hurricane Debby made landfall at Category 1 strength in Florida on August 5, but days later, its windy remnants knocked out power for nearly 25,000 people in the Green Mountain State. Last month, Hurricane Beryl landed in Texas and galloped across the country. As it faded, almost 2,000 miles from Houston, Beryl soaked Vermont with more than 6 inches of rain, creating deadly floods.
These destructive storms spooled up in an unusually active hurricane season, driven by extreme heat in the Atlantic Ocean and a shift to La Niña in the Pacific Ocean, which create the ideal air and water conditions for cyclones. But Lesley-Ann L. Dupigny-Giroux, the Vermont state climatologist, explained that there’s actually a long history of hurricanes leaving their mark across New England — even far inland from the ocean, most recently Tropical Storm Lee in 2011 and Nate in 2017.
Though states around the Gulf Coast bear the brunt of most hurricanes, even storms that enter the US from the south can have a long reach inland and northward. Beryl and Debby show how they can wreak death and destruction even after they’re downgraded to tropical storms or depressions.
Average temperatures are rising due to climate change, and because warmer air can hold onto more moisture, the most damaging elements of these storms — the flooding caused by extraordinary rainfall and towering storm surges — will continue to worsen. That means hurricanes will carve a greater swath of destruction, putting people in danger who were not vulnerable before. Understanding the mechanisms behind hurricanes is a key step in preparing for future storms and preventing their worst devastation far from the shore.
How hurricanes move over land
Atlantic hurricanes begin as waves of low atmospheric pressure moving westward from Africa over warm, tropical waters. Lower pressure from the atmosphere allows for more air to rise, carrying moisture with it. That rising, warm, damp air then cools off as it climbs, condensing into clouds that can form thunderstorms.
To turn into a hurricane — a spinning storm with wind speeds greater than 74 miles per hour — a couple more factors need to fall into place. There needs to be very little wind shear, a phenomenon where wind changes speed and direction with altitude. A strong wind shear can rip up hurricanes before they form, but when the wind is minimal, a storm can accumulate strength. The water at the surface of the ocean also needs to be around 80 degrees Fahrenheit or hotter. This creates the reservoir of thermal energy that powers a hurricane’s churn.
This year, the Atlantic Ocean was so hot that Hurricane Beryl reached Category 5 strength, with sustained winds of 157 miles per hour, earlier than any hurricane on record. It also ramped up quickly and further east than most hurricanes. Typically, the Atlantic Ocean doesn’t get warm enough to fuel such powerful storms until later in the summer or early fall.
Once they spool up, trade winds push the storms westward, and as they move over patches of exceptionally warm water, hurricanes can rapidly intensify, with wind speeds picking up by at least 35 miles per hour in a day or less.
As hurricanes approach North America, they start to face westerlies, winds that blow from west to east in the mid-latitudes. “They interact with these storms that are moving west, northwest, and kind of pick them up and start moving them northward,” said Christopher Rozoff, a project scientist at the National Science Foundation’s National Center for Atmospheric Research. That often puts hurricanes on a hook-shaped path.
But as Beryl and Debby showed, that path can extend a long distance over land, even though the hurricane does not have as much warm ocean water to feed on. What keeps the engine running? “This is a really intricate question,” Rozoff said. “We don’t have all the answers.”
That said, scientists have observed a few ways this plays out. Hurricanes like Debby are large enough that even if the bulk of it is over land, a portion can extend over the ocean, providing the storm with some of the warm water it needs to keep running.
NOAA
A hurricane may also cease to be a well-defined tropical cyclone over land, but can still carry on as a severe rainstorm. “Once a tropical system makes landfall, it will dissipate as it rains itself out and is cut off from the energy and moisture of being over a warm body of water,” Dupigny-Giroux said. “Tropical systems can transition to become ‘extra-tropical’ and ‘post-tropical’ in nature, which means that their internal characteristics are no longer those of a warm core system.”
Extratropical cyclones are spinning storms that form further from the equator and have cooler air at their cores. Instead of drawing on the ocean’s heat, the jet stream — a fast-moving, high-altitude air current — can continue driving the remnants of a hurricane over land, similar to the mechanism behind major winter storms.
Warm water basins, like big lakes or wetlands, on land can fuel hurricanes as well. “You could take the storm and put it over a land surface that is swampy or has a lot of moisture, and it can keep the storm going for some time,” Rozoff said.
Another factor to consider is whether the hurricane is holding at a steady intensity or whether it’s in the process of gaining strength. “If it’s intensifying at landfall, we often see that the storm continues to be really potent and vicious over land,” Rozoff said. On the other hand, a cyclone that’s been churning at the same pace for a while tends to weaken as it hits the coast.
As if that’s not bad enough, hurricanes climbing out of the sea and onto the shore can spawn tornadoes. Land is relatively rough compared to the surface of the ocean and that creates friction for a hurricane’s winds. As the winds closer to the ground slow down while the winds higher up keep blowing fast, it induces wind shear that can create a spinning air column that can then produce tornadoes. Because they are relatively small and form quickly, tornadoes are notoriously difficult to predict, making it harder to issue warnings to get people to shelter, further exacerbating the toll of a hurricane.
Beryl and Debby are the latest compound disasters to wallop the US
Though Beryl and Debby were extraordinary storms, part of the reason they were so damaging was that they struck places with less experience with hurricanes, and thus less preparation for them.
The hard lessons are that communities far from the ocean still need to invest in more robust infrastructure, forecasting, and early warning systems. People evacuating from the coast may have to move further to get out of the path of danger. The complication is that populations are growing, particularly in coastal regions. That means tropical storms can end up causing greater property damage and in some cases lead to more deaths. And because of climate change, hurricanes are causing higher levels of storm surge due to sea level rise and more rainfall due to warmer air. Together, these factors lead to more extensive and costly flooding.
It’s important to keep in mind that the effects of hurricanes can compound on top of other disasters. Florida’s Big Bend region, where Debby made landfall, is still recovering from last year’s Hurricane Idalia. Beryl knocked out power to Houston during a heat wave, leaving thousands of residents without cooling as the temperature and humidity reached dangerous highs. That extends the devastation of the storm beyond its wind and rainfall totals alone.
And while hurricanes hog the headlines, it’s important not to lose sight of the fact a storm doesn’t have to be a hurricane to wreak havoc. “Post-Tropical Storm Beryl actually produced less rainfall than that which led to the July 2023 flooding across Vermont,” Dupigny-Giroux said. Heavy precipitation events are also getting more severe as average temperatures rise.
As a result, many people may be far more vulnerable to disasters than they realize. But with enough planning, the worst effects can be avoided.