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Tropical lull following Maria, Lee may not last through early October

While no new threats are lurking behind Maria and Lee next week, residents of the Caribbean and United States should not let their guard down as tropical season is far over.

Maria will continue to churn up dangerous seas from the Bahamas to the East Coast of the U.S. into next week and could come close enough to graze the Outer Banks of North Carolina with rain and gusty winds.

Tropical Storm Lee came back to life on Friday evening. Lee is expected to gradually strengthen into a hurricane but will remain over the open waters of the central Atlantic Ocean.

Behind Maria and Lee, there are no new budding storms on the horizon in the Atlantic Basin.

Tropics overview Sep 23


While the onslaught of devastating hurricanes Harvey, Irma and Maria came right on cue with the typical peak of hurricane season (September 10), the lack of new development is also following climatology.

“Historically, there is a lull in activity from late September to early October,” AccuWeather Hurricane Expert Dan Kottlowski said. “That is because the conditions conducive for development collapse.”

“This time of year, the train of tropical waves streaming off of Africa lessens.”

Currently, there are just two tropical waves tracking westward across the Atlantic Basin compared to the 4-5 waves that may be present earlier in the season.

“Wind shear also increases over the central and eastern Atlantic,” Kottlowski said.

Wind shear is the changing of speed and direction of winds at different layers of the atmosphere. Strong wind shear can prevent tropical development or shred apart mature tropical storms or hurricanes.

This weekend, strong wind shear is covering a large part of the Atlantic Basin and is expected to further increase over the eastern Atlantic later next week.

“If a system comes off of Africa and faces strong wind shear, it will struggle to develop,” Kottlowski said.

While wind shear is currently low over the southern Caribbean and may lessen over the western Gulf of Mexico later next week, any system cruising these waters is expected to remain too weak to organize into a depression or storm.

The lull in tropics will allow the areas devastated by Harvey, Irma and Maria to continue the long road to recovery.

However, tropical season is far from over. There are indications that a new threat may attempt to unfold in either the Caribbean or Gulf of Mexico in early October.

“As features work into the Caribbean and Gulf of Mexico in early October, wind shear is typically low and waters are at their warmest,” Kottlowski said.

It is too early to say exactly what areas are at risk if the threat in early October unfolds. However, this is still a good time for residents and visitors along the U.S. coast and Caribbean to review what preparations would need to be taken if a hurricane threatens.

Hurricane season does not officially end until Nov. 30, and more tropical concerns are expected.

“I think we will have four more named storms this year, after Maria,” Kottlowski said. “Of these, three may be hurricanes and one may be a major hurricane."

The numbers include the risk of one to two additional landfalls in the U.S.

“The one thing to note is that westerly winds high above the surface start sinking into the Gulf of Mexico after Oct. 17, so it is very unusual for something to approach Texas after that time,” Kottlowski said.

“While past hurricanes in October have no bearing on what will happen this season, there have been some damaging hurricanes during the middle of the autumn in the eastern and southern U.S.,” AccuWeather Senior Meteorologist Alex Sosnowski said.

“These include Hazel in 1954, Wilma in 2005, Sandy in 2012 and Matthew in 2016.”