Typhoon Dujuan is within 100km of the island of Taiwan and it is expected to strike the island as a major storm.

Sustained winds of 200km/hr, the equivalent of a Category 3 on the five point Saffir-Simpson scale are expected.

The centre of Dujuan is expected to be over the east coast of the country by 12GMT on Monday.

The country’s capital, Taiwan, lies on the northeasterly quarter of Dujuan, which is where the strongest winds are expected to occur.

Dujuan was briefly a Category 4 storm at 00GMT, with winds of 230km/h. Massive seas were being generated by these winds with wave heights of 12 metres.

Dujuan is an uncommon "annular" typhoon. Most typhoons, and hurricanes, feature an intense eyewall with several rainbands spiraling away from it.

An annular eclipse features little, if any, ‘banding’. Instead, the eye is large and almost symmetrical ,and is made up entirely of intense thunderstorms.

Although annular storms are notoriously difficult to predict, Dujuan has followed the expected track towards Taiwan, and no deviation is expected before it makes landfall.

Unfortunately, annular storms have a tendency to retain their strength for longer than ‘normal’ storms. This fact, combined with the relatively slow speed of forward movement of Dujuan [about 20km/h] will allow a huge amount of rain to fall.

Up to 300mm of rain is widely expected across the island and, over the mountains, rainfall totals could be two to three times higher.

Much of Taiwan is susceptible to flooding and landslides and this will be a major concern of the emergency authorities until Dujuan is well to the west across the Taiwan Strait.

Taiwan was hit by a similar Category 3 storm in August. Typhoon Soudelor killed eight people and caused $3 billion worth of damage.

A City Risk Index by the insurers Lloyds of London, rated Taipei as the world's most financially exposed to natural disasters, including typhoons.

Typhoons hold the potential to threaten more than $80 billion in assets in the city.

After leaving Taiwan, Dujuan is expected to weaken before it makes landfall over mainland China just to the south of Fuzhou.

Flights have already been cancelled in the area, 25,000 ships have returned to port, and 80,000 people evacuated from their homes.

Source: Al Jazeera