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What kept Tropical Storm Gonzalo from becoming a hurricane? Saharan dust is the No. 1 suspect

Gonzalo was forecast to become the first hurricane of the Atlantic season. Then the dust arrived. But that won't slow Tropical Storm Hanna, which could reach hurricane strength.

Once, Tropical Storm Gonzalo seemed destined to become the first hurricane of the 2020 Atlantic season.

Then came dust from the Sahara Desert.

The Trinidad and Tobago government’s weather service released an advisory Thursday that attributed Gonzalo’s weakening to the plume of dust that’s moving from the Saharan Desert in Africa toward the U.S. and the Caribbean.

“Over the last several hours, Tropical Storm Gonzalo has become less organized and has weakened slightly,” the agency said. “Saharan dust around the system is inhibiting further development and intensification.”

Related: How dust from the Sahara Desert put a temporary pause on hurricane activity this season

Meanwhile in the Gulf of Mexico, Hanna reached tropical storm strength on Friday morning and is expected to make landfall in Texas on Saturday afternoon, according to the National Hurricane Center. There’s a possibility it could strengthen into a Category 1 hurricane before making landfall.

In the Atlantic, the hurricane center on Wednesday forecast that Gonzalo’s wind speeds would reach the 74 mph threshold needed to be declared a Category 1 hurricane by Friday as it moved into the Caribbean Sea. It issued hurricane watches for a number of islands who were in storm’s projected path.

But the Saharan dust has slowed Gonzalo’s wind speeds down, reducing them from 65 mph on Wednesday to 45 mph as of 2 p.m. Friday. The storm is now expected to dissipate completely by the middle of next week, according to the hurricane center, which forecasts that it will fail to make it out of the southern Caribbean Sea.

The hurricane center said Gonzalo was 445 miles east of the Windward Islands on Friday and is continuing to weaken. As a result, a number of countries, such as Barbados and St. Vincent and the Grenadines, replaced their hurricane watches with tropical storm warnings instead.

The Saharan dust is called the “Saharan Air Layer” by the National Oceanic and Atmospheric Administration. It’s a common phenomenon that lifts dust particles from the desert up 5,000 to 20,000 feet above the earth.

When the dust enters an area, it chokes up all moisture, causing tropical systems to weaken when present — and when it’s there from the start, it can stop cyclones from forming all together.

A National Oceanic and Atmospheric Administration model shows the plume of dust that’s weakening Gonzalo traveled from off the coast of Africa this week and will reach Florida by 5 a.m. Sunday. While the dust will likely put an end to Gonzalo, it’ll arrive too late to help weaken Hanna in the Gulf.

Hanna brought increased rain chances in Florida earlier in the week but is now aimed at Texas, where a tropical storm warning was enacted on Friday. The hurricane center predicts that Hanna, which had sustained winds up to 50 mph, will continue to strengthen until it makes landfall.

While Saharan dust helps quell potential hurricanes, NASA says it can also cause poor visibility and air quality wherever it looms.

“It affects human health by causing irritation of eyes, nose and throat,” according to a July 17 article from the NASA Earth Science Division. “It often contains fine particulates of silica and other minerals that are of a size that can easily infiltrate and irritate lung tissue.”

The dust can also cause a thick haze to hang in the air over Texas, said National Weather Service meteorologist Rick Davis, who is in the Ruskin office. It sometimes feeds into deadly algae blooms in the Gulf of Mexico, like in 2018, when the dust contributed to scores of sea life deaths around Florida for more than 14 months.

While the dust can bring both bad and good, perhaps the most obvious sign of its arrival this weekend will be from looking at Saturday and Sunday’s sunsets.

“One unique aspect of the dust will be our sunsets being incredibly vivid,” Davis said. “Saharan dust is orange and red, so as the sun sets through the haze you’ll get bright, brilliant sunsets.”

JIM DAMASKE | Times The setting sun draws a large crowd to the waters edge on Clearwater Beach. - Sunsets and a movie at Pier 60 on Clearwater Beach. Catch a sunset then sit down in the grass near Pier 60 and watch a free movie. Step up all in was playing Friday night and Men in Black 3 is scheduled for Saturday night. Every Friday and Saturday a movie is scheduled. They start about 6:30. 1/2/2015 [ Tampa Bay Times (2015) ]

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