September 25, 2024
4 min learn
What Makes Hurricane Helene Such a Harmful Storm?
Hurricane Helene is a big storm set to convey substantial storm surge to the coast of Florida, in addition to wind and rain-driven flooding up into Tennessee and South Carolina
Hurricane season isn’t performed with the Gulf Coast, it appears. One more storm, Helene, is heading for Florida a bit of greater than two weeks after Francine walloped Louisiana. Helene is massive—and is ready to convey as much as 15 toes of storm surge within the state. It’s additionally anticipated to trigger excessive downpours effectively inland, with the best potential for flash flooding within the southern Appalachian Mountains.
Although Helene shaped simply after the mid-September peak of the Atlantic hurricane season, that is nonetheless prime time for storms as a result of ocean waters have loads of warmth to gas them after months of summer time solar. This hurricane continues a resurgence in storms that started with Francine in early September following weeks of comparatively little exercise. The lull got here after the season began with a bang with Hurricane Beryl, which turned the earliest Class 5 storm on report within the Atlantic basin.
Now Helene is barreling into the Gulf of Mexico, the place the setting is predicted to be near best for the storm to strengthen. Helene is forecast to turn into a significant hurricane earlier than it makes landfall someplace in Florida’s Large Bend space (the criminal between the state’s panhandle and its principal peninsula).
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One key menace from Helene can be storm surges, that are anticipated to achieve 10 to fifteen toes above floor degree within the worst-hit areas of the Large Bend. Decrease, although nonetheless doubtlessly damaging, surge ranges are forecast as distant from the middle of the storm because the southern tip of Florida. One cause for the big surge footprint would be the storm’s dimension, which is predicted to be within the prime 10 p.c of hurricanes at related latitudes.
Helene can be so massive partially as a result of “it’s beginning out massive,” says Kim Wooden, an atmospheric scientist on the College of Arizona. Additionally, the storm’s heart is presently threading the needle between Cuba and Mexico; this retains it over water, permitting the convection that powers the core of tropical techniques to proceed getting gas within the type of warmth and moisture. In the meantime the winds swirling round that heart are travelling over land, the place they encounter friction—“and that strikes power and momentum round” in a method that may improve the scale of the storm, Wooden says. Lastly, when the storm strikes into the gulf, it would have ample moisture and warmth, and Wooden notes there’s some analysis that means that extra humid environments yield larger hurricanes. For example, they cite Hurricane Katrina, which grew a lot larger after it emerged into the gulf than it had been earlier, when it was within the Atlantic to the east of Florida. “The Gulf of Mexico can assist larger storms,” Wooden says.
These heat, moist circumstances—together with comparatively little wind shear, which might disrupt a storm’s heart—are additionally anticipated to trigger Helene to steadily intensify. It’s prone to turn into Class 3 or stronger earlier than it makes landfall. There’s a powerful likelihood it may endure what is known as fast intensification, which suggests a storm’s sustained winds leap by not less than 35 miles per hour in 24 hours.
Whether or not Helene does so relies upon partially on all of these exterior environmental elements, in addition to the storm’s inside construction. Hurricanes that develop a closed “eye wall” of thunderstorms round their heart “eye” can use warmth extra effectively and thus develop, Wooden explains. That is one cause consultants and forecasters are watching detailed satellite tv for pc imagery that helps them view what is occurring on the heart of the storm, “virtually like an x-ray to see what’s occurring beneath the cloud tops,” they are saying.
Helene’s winds will possible trigger issues unusually far inland—with tropical-storm-force winds doubtlessly reaching into northern Georgia—as a result of the storm can be shifting pretty briskly. Storms that transfer quicker after making landfall don’t lose power as rapidly, Wooden says.
Helene can even convey substantial flooding threats from heavy rains far inland. The areas most definitely to be affected lengthen northward from the Gulf Coast to the southern Appalachians, the place the menace can be at its highest. That is partly as a result of that area has been enduring a drought, so the soil is dry and packed. Meaning a lot of the rain will merely run off, says Derek Eisentrout, a meteorologist on the Nationwide Climate Service’s workplace in Morristown, Tenn. Moreover, the mountainous terrain means rain can rush down slopes into lower-lying valleys, he says.
Local weather change can also be taking part in a job in growing the threats from hurricanes: Rising seas add to surge quantities, and storms now produce increased rainfall totals than they did previously. And there’s proof {that a} increased proportion of hurricanes are reaching the best intensities, so storms are additionally anticipated to endure fast strengthening due to local weather change.
Forecasters observe that anybody in Helene’s path ought to pay shut consideration to native forecasts and orders from native officers about evacuations and areas to keep away from. Wooden notes that the Nationwide Climate Service additionally has useful Hurricane Threats and Impacts Graphics, which let folks toggle between completely different threats—reminiscent of flooding and winds—and click on to see the standing of their particular space.
Further reporting by Meghan Bartels.