Scientists study the nursery of tropical cyclones
Jason Dunion led a historic deployment of a National Oceanic and Atmospheric Administration Hurricane Hunter aircraft to the Cape Verde Islands to survey the region where many of the most powerful hurricanes originate.
The Hurricane Hunter plane had never flown so far east – the Cape Verde archipelago just off the west coast of Africa, 3,800 miles from their base in Lakeland, Florida.
But in early August, one of the planes, a modified Gulfstream IV jet operated by the National Oceanic and Atmospheric Administration (NOAA) and fitted with a suite of advanced surveillance equipment, was deployed for the very first time in the chain of islands, allowing a team of scientists on board to study an area known as the nursery of some of the fiercest storms in the Atlantic.
“About 80-85% of major hurricanes – Category 3 and above – that impact the United States originate in this region, beginning with thunderstorms that drift off the West African coast and build into tropical waves. that pass over or near the Cape Verde Islands,” said Jason Dunion, a scientist at the University of Miami’s Cooperative Institute for Marine and Atmospheric Studies (CIMAS), who was part of the historic deployment. this summer from a NOAA hurricane hunter to the island nation to study the genesis of the cyclonic tropics.
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Storms that form near these islands are called Cape Verde hurricanes. Many are powerful and vivacious. And when they hit the ground, they are usually destructive.
On August 16, 1992, Cape Verde waters spawned the tropical depression that would become Hurricane Andrew, which devastated southern Miami-Dade County as a powerful Category 5 cyclone.
Hurricane Irma, the first Category 5 storm of the 2017 season, also originated in these waters. After hitting a chain of small islands in the Caribbean, the storm, which stretched 650 miles from east to west, impacted at least nine US states, downing power lines and turning roads into rivers.
But despite Cape Verde’s reputation as a breeding ground for some of the most intense storms in history, “we still don’t know as much about the region as we should,” Dunion said. “So we wanted to get closer to those islands to investigate the beginning of the whole process rather than waiting days for those storms to come our way.”
As director of this year’s Hurricane Field Program, a collaboration between CIMAS, part of the University’s Rosenstiel School of Marine, Atmospheric, and Earth Science, and NOAA, Dunion coordinated and conducted three eight-hour search missions over the skies of Cape Town. Green.
Flights operated from Amílcar Cabral International Airport on the island of Sal. Once airborne, Dunion and a crew of nine other scientists launched weather reconnaissance devices called dropsondes that measured tropical disturbances in the region.
Sophisticated onboard instruments identified areas of potential storm activity, generating diagrams showing researchers where to deploy their consumables. The devices, launched from altitudes as high as 45,000 feet, transmitted data that will not only help reveal the dynamics of storm formation, but also improve forecasts of hurricane intensity and track, a said Dunion.
The three days of flights also gave Dunion the opportunity to continue research into the Saharan Air Layer, an extremely dry and dusty air mass that forms over the Sahara Desert in late spring, in summer and early fall.
“These Saharan dust outbreaks rush off the West African coast every three to five days; and they’re huge, about the size of the lower 48 states,” Dunion said, noting that the dust is reaching as far as Miami, the Gulf Coast and even Central America. “They’re traveling about a mile above the surface, the winds are very strong, and the air is dry and warm. It’s a trifecta that suppresses hurricane activity. So we’re studying how these Saharan dust storms can interact with the tropical waves that come from the African coasts.
The search, along with some of the technology that makes it possible, “simply didn’t exist 30 years ago when Andrew struck,” Dunion said. “We’ve come a long way.”