Isaac has weakened to a tropical depression, said the National Hurricane Center.

At 5 p.m. Thursday, Isaac was about 35 miles west-northwest of Monroe, Louisiana, with maximum sustained winds at 35 mph. It was moving north-northwest at 12 mph.

PHOTOS: Isaac at Katrina landfall site

Isaac was expected to turn north late Thursday or early Friday.

On Thursday, NOAA released a picture showing flight paths of hurricane hunters through Isaac.

As three tropical systems churn, Local 10 Hurricane Specialist Max Mayfield wanted to remind everyone that we are in the peak of hurricane season.

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Leslie gains strengthen over open Atlantic

Tropical Storm Leslie formed in the open Atlantic Ocean on Tuesday afternoon.

In the National Hurricane Center's 5 p.m. advisory, Leslie was about 1,060 miles east of the Windward Islands with maximum sustained winds of 45 mph. It was moving west at 21 mph.

Leslie was expected to move west-northwest with a decrease in forward speed over the coming days. The storm was forecast to become a hurricane by the weekend.

The National Hurricane Center said Leslie is the second earliest formation of the 12th named storm on record in the Atlantic Basin, eclipsed only by Luis in 1995.

Kirk continues to strengthen

Kirk continued to strengthen over the open Atlantic.

In the NHC's 5 p.m. advisory, Kirk was about 1,065 miles northeast of the northern Leeward Islands with maximum sustained winds of 90 mph. It was moving north-northwest at 13 mph.

Kirk was forecast to turn toward the north on Friday.