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Rapidly developing tropical system taking shape over the Atlantic

By Alex Sosnowski, AccuWeather, Accuweather.com
Rapidly developing tropical system taking shape over the Atlantic
Potential Tropical Cyclone Five is currently spinning in the central Atlantic halfway between Africa and the Windward Islands. Image courtesy of NOAA

July 1 (UPI) -- A rapidly developing feature in the Atlantic may soon set a new record for the earliest E-named storm in the basin's recorded history.

AccuWeather meteorologists have been monitoring two features that could become the next tropical system of the 2021 Atlantic hurricane season, and on Wednesday, one began to show greater signs of organization.

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The feature, initially dubbed invest 97L by the National Hurricane Center, was labeled as Potential Tropical Cyclone Five around 5 p.m. EDT Wednesday. It was then upgraded to Tropical Depression Five.

It is currently spinning in the central Atlantic halfway between Africa and the Windward Islands with maximum sustained winds of 35 mph and is traveling west-northwest at 21 mph. While this feature is closer to earning the E name of the season than the second, the latter still warrants watching as well.

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Should a tropical storm form, it would be the fifth of the 2021 season. The next name on the list for this year is Elsa, and if Tropical Storm Elsa forms prior to Tuesday, it would be a record for the earliest E-named storm ever to form in the basin.

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As parts of the Lesser Antilles were being affected by drenching showers and gusty thunderstorms from one tropical disturbance, dubbed 95L by the NHC, that is on AccuWeather's "watch list," PTC 5 was located a few hundred miles farther west and had been showing signs of rotation in its cloud shield since Tuesday.

Tropical storm watches are currently in effect for Barbados, St. Vincent and the Grenadines, St. Lucia and Martinique, according to the National Weather Service.

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"By Thursday morning, it is expected to become a tropical storm," said AccuWeather Meteorologist Derek Witt.

Soon after the disturbance catches on, it could strengthen quickly into a hurricane as it approaches the Windward Islands.

This disturbance, commonly called a tropical wave by meteorologists, is part of a long series of such features that roll westward from Africa across the Atlantic and often cross into the eastern Pacific. A small fraction of these waves goes on to develop into tropical depressions, tropical storms and hurricanes under the right atmospheric conditions.

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What is so unusual about this season so far is the number of robust candidates for organized tropical systems originating from the Africa wave train so early. Usually, meteorologists expect to see their first strong candidate from this area during August and not late June or early July. There have already been a few other disturbances in this zone that AccuWeather forecasters have monitored for development in June, but none of them became organized enough to be named.

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The tropical disturbances that originate from Africa are also referred to as Cabo Verde systems, named for a group of islands just off the coast of the continent. Cabo Verde systems constitute the backbone of the Atlantic hurricane season with multiple tropical storm and hurricane candidates typically emerging in the months of August, September and October. Most of the small number of systems that develop prior to this time of the year originate in waters close to Central and North America and are often called "homebrew" storms.

"Following the showers and thunderstorms associated with 95L into early Thursday, portions of the Lesser Antilles are likely to start feeling the effects of PTC 5 on Friday," Miller said.

The weather on Friday in portions of the Leeward and Windward islands could be in the form of tropical storm or perhaps hurricane conditions with rounds of heavy rain, gusty winds, building seas and dangerous surf.

While the somewhat less organized disturbance (95L) was encountering increasing wind shear and dry air, PTC 5 was in a zone more favorable for development in its wake.

"Wind shear is currently low, and there is more moisture available to PTC 5," Miller said.

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Should the system hold together, it is forecast to drift west-northwestward over the open waters of the Caribbean Sea spanning July 3-5.

Once in the Caribbean, it could continue on to the Gulf of Mexico or possibly turn more to the north and cross one of the islands that make up the Greater Antilles, such as Hispaniola or Cuba, and re-enter the southwestern Atlantic near the Bahamas or Florida sometime between July 5 and 7. Waters in all of these basins are generally in low to middle 80s F which is plenty warm enough to support tropical development or sustain an established tropical system.

The track of the system next week will be subject to the strength of the tropical feature itself, as well as the strength and position of non-tropical systems in the region, including an area of high pressure over the western Atlantic and storms, fronts and jet streams near the United States.

"Sometimes systems such as this struggle for a time over the eastern and central Caribbean, known as the 'graveyard,' due to wind shear, dry air from South America and the mountainous terrain of the big islands of Puerto Rico and Hispaniola," AccuWeather senior meteorologist Bill Deger said.

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However, even if this system plateaus or weakens for a time, it does not necessarily mean it will dissipate entirely. Tropical systems that struggle for a time in the eastern part of the Caribbean can rebound farther west or north days later.

Meanwhile, 95L, the disturbance in front of PTC 5, was looking a bit less organized on Wednesday compared to the start of the week. This tropical wave was encountering wind shear, dry air and dust from the Sahara Desert as it was passing through the Lesser Antilles on Wednesday.

Since 95L is situated in a zone with more wind shear to start and may interact with the islands of the northern Caribbean early on, development to a tropical depression or storm is significantly lower, when compared to PTC 5. Further weakening of 95L may result in meteorologists dropping it from the tropical watch list.

At this time, all interests in the Caribbean should closely monitor the progress of PTC 5 and keep an eye on 95L for the time being. Interests in the southeastern U.S. should also monitor the progress of both systems for potential impacts beyond the first few days of July.

2021 keeping pace with record 2020 Atlantic hurricane season

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The formation of a named tropical system or two is not highly unusual by late June, but on average, the second named storm does not brew until early August, according to the NHC. To have five such systems by late June or early July is teetering on record territory. The average date for the fifth storm to form is Aug. 31.

Last year, Dolly missed the record for the earliest fourth-named storm, or D-storm, by just a few days. In 2016, Danielle formed on June 20, and Dolly formed three days later in 2020 on June 23.

This year's Tropical Storm Danny formed on June 28.

Every storm after Dolly last year set an early-formation record. The "E" storm, which was Edouard, formed on July 6, 2020. With two potential candidates in the next six days, there is at least a chance of a record being broken should Elsa take shape.

The 2020 Atlantic hurricane season was the busiest on record with 30 named storms that required the use of the Greek alphabet, once the last name and letter "W" on the list was used up. That was the second and last time the NHC will tap into Greek letters to name storms that extend via the original designated list.

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The 2021 season is forecast to fall short of the number of named systems from 2020. However, AccuWeather forecasters say that to have a significant amount of tropical disturbances that are originating from Africa this early is a concern.

Since these long-track disturbances tend to spend more time over water, they tend to have more time to organize, develop a circulation and strengthen, when compared to homebrew storms. Because of that, they could potentially pose a more significant threat to lives and property as they approach land areas.

In addition to these two main areas of concern, patches of showers and thunderstorms have continued to erupt over the Gulf of Mexico this week.

"The Gulf of Mexico will probably remain an area where there is at least a very low risk of a weak system popping up very close to the coast over the next week or so," AccuWeather Senior Meteorologist Dave Houk said.

AccuWeather meteorologists are forecasting 16-20 named systems for the Atlantic basin for the 2021 season with seven to 10 hurricanes and three to five direct impacts on the U.S. Both Danny from June 28-29 and Claudette from June 19-23 tracked over the Southeastern states.

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