What was once a broad cluster of storms in the Caribbean on Monday slowly coalesced into a hurricane on Wednesday. The intensity will ramp up on Thursday.
In the span of 12 hours, Helene is expected to transform from a Category 1 hurricane Thursday morning to a Category 3 storm by Thursday afternoon, and forecasters warn it could intensify even more before landfall.
If the storm develops the way forecasters are predicting, it would signify “a pretty aggressive intensification,” Brian McNoldy, a hurricane researcher at the University of Miami, said this week.
Behind this potential rapid intensification is the “record-to-near-record-warm” ocean temperatures — which is “like high-octane jet fuel” for the storm — and a very fast change in wind heights, Mr. McNoldy said.
This month, the Gulf of Mexico is obliterating records for Ocean Heat content, according to records by Dr. McNoldy. Ocean heat content is a sort of fuel for hurricanes — the higher the amount, the greater the influence it can have on storms like Helene.
The water Helene is traversing Thursday is roughly the ideal temperature for a warm bath. The storm is moving directly over the Loop Curren — a steady, strong current of warmer water that moves from the Caribbean and loops like a horseshoe in the eastern Gulf before moving through the straights of Florida. Storms traversing the Loop Current, like Hurricane Michael in October 2018, often get enough energy from the warm water to rapidly intensify.
In addition to the warm ocean temperature, storms tend to intensify “when winds don’t change a lot with height,” Mr. McNoldy said. Wind shear can separate the top of the center of the storm from the bottom, which keeps the eye from strengthening. With little shear forecast over the Gulf Thursday, the storm will likely intensify quickly.
At a storm briefing on Tuesday morning, Gov. Ron DeSantis of Florida expressed concern over the speed of the storm’s development.
“They’ve never in their history forecasted a major hurricane at this stage of development,” he said. “When it’s over the Gulf, especially the more north it goes rather than east, it has a chance to have a rapid intensification.”
Mr. McNoldy pleaded for people to re-evaluate how they were looking at weather forecast maps that often show the likely path of the storm as a cone stretch onto land.
But many people misinterpret the cone as “if I’m inside the cone it’s not good,” but “if I’m outside of the cone I’m fine,” he said. “That is absolutely not true.”
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