Flash Flood Watch

US East Coast may experience close encounter with tropical system early next week

By Alex Sosnowski, AccuWeather senior meteorologist
August 12, 2017, 5:13:51 AM EDT

A batch of thunderstorms of interest over the central Atlantic, dubbed 99L, has the potential to develop and travel into waters near the United States next week.

When clusters of thunderstorms in the Atlantic Ocean have a chance to become a tropical depression or storm, they are assigned a number between 90 and 99. The "L" designation refers to a system under investigation in the Atlantic.

How much development occurs is uncertain at this time, according to AccuWeather Hurricane Expert Dan Kottlowski.

99L track 8.12 AM

Coastal, cruise and shipping interests in the western Atlantic should monitor the progress of this system.

"Dry air and strong winds aloft will inhibit development of 99L through Saturday," Kottlowski said.

Nintey-nine L will be guided around the clockwise flow of a large area of high pressure over the middle of the Atlantic Ocean.

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"We expect 99L to move northwestward and into a zone more favorable for tropical development just northeast of the Bahamas during Sunday and Monday," Kottlowski said.

In this area, 99L could organize into a tropical depression and possibly Tropical Storm Gert.

Depending on the shape of the high pressure area to the east and the speed of a non-tropical storm approaching from the west, a more northward turn is likely, Kottlowski stated.

"At this time, the more likely scenario is for the tropical system to stay offshore and not directly reach the U.S.," Kottlowski said.

If the system strengthens to a tropical storm or hurricane, surf would build from the Bahamas this weekend to the Atlantic coast of the U.S. and Bermuda early next week. This can occur even if the storm remains as sea.

The non-tropical storm could stall and result in torrential rain and increase the risk of flooding in part of the eastern quarter of the nation during the first part of next week. This can occur even if the two systems remain separated.

Static SE 99L Flood Risk

The greatest risk of flooding rainfall may be from Delaware to Georgia during the first part of next week.

Portions of the Southern states will be inundated with downpours prior to the tropical system's approach and its departure.

The system that attempted to brew just east of Florida has lost its chance to develop.

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