TOKYO, Sept 3 (Reuters) - A powerful typhoon heading northwest towards Japan's Okinawa islands weakened enough by Saturday to lose its super-typhoon status, but the storm remains extremely strong and could threaten Japan's main islands.
Typhoon Nabi -- Korean for "butterfly" -- was on Friday a Category Five storm, technically the same strength as Hurricane Katrina which devastated New Orleans just before the eye of the storm made landfall.
According to the website of the Tropical Storm Risk group at University College London,
www.tropicalstormrisk.com, Nabi had weakened to Category 4 on Saturday. But it was projected to strengthen to super-typhoon status again in 24 hours.
An official at Japan's Meteorological Agency said the storm may pass over Okinawa on Monday and near the southernmost main island of Kyushu early on Tuesday, possibly making landfall, but that the worst of its fury is likely to have been spent by then.
"This is an extremely strong storm, and could bring a lot of rain to Japan, but I think that in terms of overall destructive force it has already passed its peak," he said.
"We will still have to be extremely careful, though."
At 0100 GMT, Nabi was some 600 km (372.8 miles) southeast of Minami Daitoshima, an island around 1,100 km (690 miles) southwest of Tokyo.
Nabi was moving northwest at 15 km an hour, "about the speed of a person riding a bicycle", the Meteorological Agency official added, and was likely to pass over Okinawa sometime on Monday.
Although it is still too early to predict the storm's ultimate course, Nabi could make landfall on Kyushu before passing across it to strike the Korean peninsula.
Japan's main islands were hit by a record 10 typhoons in 2004 that left around 170 people dead or missing and caused billions of dollars worth of damage. This year, however, only one tropicl storm has made landfall.
