Taiwan's Central Weather Administration (CWA) has issued a land warning for Typhoon Bavi, which is expected to bring up to 900 mm of rain to northern mountain areas by Sunday July 12, and generate waves of more than six metres along the coast.

The CWA issued the land warning at 5:30 a.m. on July 10, after placing the storm under a sea warning the previous afternoon according to local media Focus Taiwan. It said Bavi would have its greatest impact from Friday evening, July 10 through Saturday, July 11.

The agency forecasts the typhoon will pass through waters just north of Taiwan – a short distance from the country’s largest city, New Taipei and its capital, Taipei with a combined population of around 7mn.

As of 8 a.m. on July 10, Bavi was still around 430 miles east of Eluanbi, Taiwan's southernmost point, moving northwest at 15 mph.

The storm had maximum sustained winds of 100 mph, with gusts of up to 123 mph, and a radius of about 235 miles.

The size of Bavi's – the largest typhoon to hit Taiwan since 1987 according to one CWA forecaster – means it will have a significant impact, regardless of whether or not it makes landfall.

In the heavily populated north of the island, cumulative rainfall though to July 12 is forecast at 600-900 mm in mountainous areas of New Taipei, Taoyuan, Hsinchu County and Miaoli County, with lower-lying areas of predicted to get 500-700 mm.

Winds are expected to strengthen as the storm approaches with sustained winds and gusts of force 9-11 on the Beaufort scale expected across Taiwan and its offshore islands Focus Taiwan adds.

The CWA has also issued its first "mega wave" warning since introducing the alert system this typhoon season, with the warning taking effect along much of the east coast where waves exceeding six metres are expected.

Waves of up to 7 metres were recorded off the southeast of Taiwan late on June 9.