Summer hurricane shield set to fade
Florida’s dusty safety blanket will lower itself next week
Florida’s dusty shield against hurricanes is lowering itself next week at a time when meteorologists predict to see one of the most extreme and active tropical weather seasons ever.
Gulf and Caribbean communities were covered this summer by a hurricane safety blanket, thanks to the annual migration of beige African dust known as the Saharan African Layer, according to the National Oceanic and Atmospheric Administration.
The layer is responsible for sucking up moisture in the tropical Atlantic and creating a large increase in vertical wind sheer in the upper atmosphere, preventing storms from organizing.
Every year, the SAL blows a large plume of dust across the ocean, tightly gripping the area in a choke hold and bringing the tropical formation factory to a grinding halt. This year meteorologists observed the largest dust plume to cross the Atlantic in 20 years. The cloud kept conditions surrounding the Caribbean and Gulf Mexico unfavorable for tropical development.
Earlier this summer, scientists observed the SAL moving over 2,000 miles between June 13 and June 18, thanks to westerly winds whipping it up to the atmosphere and across the ocean, according to NASA. At its greatest distance, it covered 5,000 miles, equal to the entirety of the continental United States, said Jason Dunion, meteorologist at the University of Miami at NOAA’s Atlantic Oceanographic and Meteorological Laboratory Hurricane Research Division.
Aside, from hurricane prevention, the dust serves other purposes as well including fertilizing the soils in the Amazon and building the beaches in the Caribbean, according to NASA.
It’s hard to say how many storms the layer has actually prevented from forming, however, but experts can say that July’s Tropical Storm Gonzalo didn’t become 2020’s first hurricane thanks in large part to having to battle a tsunami’s worth of brown dust.
The dust cloud’s windy dryness is expected to peak by Aug. 15, allowing tropical storms much more breathing room, Dunion said.
“Hurricane models don’t predict out more than a week, but there’s consistently a lot of data showing that by mid-August, this is the point where the SAL is smaller and not reaching as far,” Dunion said. “Aug. 15 is the switch point where we expect a ramp down to start happening.”
The high pressure ridge hanging over the Atlantic is the “conveyor belt” responsible for pushing the SAL westward, but the pressure was expected to peak by July, Dunion said. Meaning, the conveyor pumping hurricane face masks for the tropics, is slowing down.
This year has already proven to be an unusual hurricane season, with the ninth named storm having been formed by August. Usually the ninth storm of the season isn’t observed until Oct. 4.
SAL’s demise comes at a bad time for coastal residents who received a prediction last week from the NOAA, which gave its largest forecast for total number of named tropical storms in a single season. Hurricane specialists are predicting conditions are ripe enough for 19 to 25 named storms to form before the season’s end on Nov. 30.
The only hurricane season to have more was 2005 when 28 storms developed, the same year that saw Hurricane Katrina, Rita and Wilma bring devastating wind and water to the United States.
Scientists think the fact the season’s record-breaking hyperactive forecast comes on the heels of the largest African dust plume could be connected, but there’s not enough data to definitely say. What raises eyebrows is the location of the “hurricane nursery;” a location off the coast of Africa where half of all hurricanes come from and is the origin point of 80% of major hurricanes. Its location is just north of where the SAL lifts off from.
NOAA had planned a major collaboration with NASA to study the dust plumes in the peak of season; last July, but the operation was stalled until next year because of COVID-19 concerns, Dunion said.
“It’s very disappointing. We put a lot into planning, and we haven’t been out there since 2006 to study the SAL or cyclones,” Dunion said. “We have technology that is far advanced since the last time we were there, so we’re eager to see what we can learn. But we’ll push on. We should be out early next July. It’s something we need to learn a lot more about.”