Washington, Aug 31 (IANS): The catastrophic hurricane Harvey has weakened to a tropical depression with its centre now located in southwest Louisiana, but continues to cause heavy rains, the US National Hurricane Centre (NHC) announced.

In the public advisory released late Wednesday night, the NHC indicated that Harvey has maximum winds of 55 km/h and is located 15 km southwest of Alexandria, Louisiana, reports Efe news.

It moves to the northeast with a speed of 13 km/h, and is expected to gradually weaken in the next 48 hours while moving further inland, the NHC said.

According to a storm track forecast, Harvey's centre will move through Louisiana on Wednesday night, and then pass through northwest Mississippi on Thursday.

"Catastrophic and life threatening flooding will continue in and around Houston, Beaumont/Port Arthur, eastward into southwest Louisiana for the rest of the week," the NHC said.

It also warned that Harvey could produce additional rainfall accumulations of seven to 15 cm from southwest Louisiana and the border of eastern Texas northwestward into Kentucky until Friday, with isolated amounts of up to 25 cm.

The NHC strongly advised people they "do not attempt to travel in the affected areas" and "do not drive into flooded roadways".

Harvey, which made landfall in Texas on the night of August 25 as a powerful Category 4 hurricane, has left catastrophic floods in Texas, leaving at least 20 people dead and over 17,000 displaced.

Meanwhile, Irma, the ninth tropical storm of the Atlantic hurricane season, formed near the Cape Verde archipelago on Wednesday, is expected to intensify into a hurricane on Friday while continuing its course towards the Caribbean.