Tropical Storm Leslie was forecast to strengthen into a hurricane on Friday, the U.S. National Hurricane Center NHC.L said, but would remain out at sea. Leslie was 940 miles (1,510 km) east of the Leeward Islands of the West Indies, moving west-northwest overnight.

Another storm, Hurricane Kirk, whipped up winds of 105 mph and could strengthen, the NHC said, but, churning the sea about 870 miles (1,395 km) east-southeast of Bermuda, it posed no risk of reaching land and would start weakening on Saturday.

Hurricane season brought the first big test to Louisiana's flood defences, installed after 2005's Hurricane Katrina almost destroyed New Orleans, with Isaac blowing through the state exactly seven years on.

Isaac never came close to the power of Katrina, which was a Category 3 hurricane when it smashed into New Orleans on August 29, 2005.

But Issac still left much of Louisiana flooded and without power as it blew north, weakening to a tropical depression.

Issac could still bring heavy downpours and further lowland flooding before moving into the central United States - where rain is badly needed - over the next few days.

Some 700,000 homes and businesses in Louisiana and Mississippi were still without power on Thursday, down from a peak of about 1 million. As winds subsided, crews were able to start assessing damage to power lines.

Losses from Issac are estimated at between $500 million and $2 billion in insured onshore losses, according to estimates by two firms that project damage for the insurance industry. (Writing by Robin Pomeroy; Editing by Louise Ireland)

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