Hurricane shield to end

Bubble over Atlantic kept storms at bay

Florida and the rest of the coastal U.S. have had a bubble of protection from hurricanes so far this year, but it’s about to burst as the Atlantic heads into what’s forecast to be a record-breaking season.

Dust carried across the ocean from Africa is disappearing, sea temperatures are creeping warmer, and storm-killing wind shears are going away — changes that are combining to clear the way for storms to form and grow stronger.

Two updated seasonal forecasts issued last week broke the bad news. The National Oceanic and Atmospheric Administration predicted as many as 25 storms — more than the agency has ever forecast — and Colorado State University forecast more storms than any season except 2005, the year of Hurricanes Wilma and Katrina.

“It’s the switch-point in the Atlantic, sea surface temperatures, also the winds are more favorable,” Dr. Jason Dunion, a scientist with the University of Miami and NOAA, said. “The conditions are really becoming ripe for more activity.”

The Saharan air layer forms every year over Africa starting in mid-June, carrying a plume of dust over the Atlantic that slows the development of storms. The winds, which are typically a mile or two above the surface, can reach speeds of 25 miles per hour, or even higher. Dunion said that’s enough to rip a storm apart.

That air layer is also dry, which starves storms of moisture they need to become hurricanes.

“In late June, it was some of the most active [Saharan air layers] we’ve seen on record,” Dunion said. “It was difficult for sure for tropical cyclones to really intensify because these outbreaks were so large and they were covering most of the Atlantic while they were coming across.”