Tropical storm Saola, now a typhoon, is likely to intensify to Category 3 strength as it continues on a northwest track through the Philippine Sea heading toward northeastern Taiwan.

While the current forecast track predicts that the centre of Saola will pass just north of Taiwan, strong winds, substantial rainfall, possible flooding and dangerous surf conditions are expected to develop across much of the island's north as the outer bands of the system spread inland.

The storm centre was not expected to hit land, but Saola could bring heavy rainfall to northern, northeastern and eastern Taiwan, said the Central Weather Bureau.

In Kaohsiung, fishing boats and passenger vessels were ordered to return to port to avoid the typhoon.

Forecasters predict rain through to Friday, and warn of possible landslides and road collapses.

Typhoon Saola, named for the rare mammal found in Laos and Vietnam, dumped torrents of rain as it swept past the Philippines, killing at least 10 people, and displacing 145,000 others by Tuesday.