The northern island of Luzon is preparing for its biggest storm of 2015.

Typhoon Koppu continues to intensify ahead of landfall on the east coast of Luzon at Baler Bay at around 01:00 GMT on Sunday.

Winds within the typhoon’s circulation are in excess of 210km/h, making it the equivalent of a Category 4 hurricane, on the five-point Saffir-Simpson scale.

Koppu will hit as a Category 3 to Category 4 storm, with winds strong enough to cause severe damage. Trees will be uprooted, buildings damaged or destroyed, and a major storm surge will inundate sections of the coastline.

An even greater threat, however, is posed by the torrential rainfall which is expected to fall. Satellite imagery from the Tropical Storm Measuring Mission has analysed rainfall within Koppu’s southwestern quadrant of 133mm/hr.

Although this intensity is unlikely to be maintained over land, Koppu will become very slow moving after making landfall. It is expected to maintain its circulation, albeit as a weaker tropical storm, for the following 48 to 60 hours.

This will allow huge amounts of rain to fall. Computer models predict accumulations of 600mm across quite a wide area of central northern Luzon. Over the more mountainous areas that total could rise to 900 to 1,000mm. For comparison, London, UK, has an annual rainfall total of just under 600mm.

On a more positive note, the country’s capital, Manila, is likely to be to the southeast of this torrential rain. Nevertheless, there could be some flooding in the capital as rainfall totals reach 250mm.

President Aquino appeared on national television to issue a warning to the country’s citizens to prepare for Koppu.

Aquino said that the Social Welfare Department had estimated that 7.5 million people would need help either before or after Koppu’s arrival.

The last time comparable rainfall fell on Luzon was during August 18 to 21 in 2013 when 600mm of rain fell as the monsoon was enhanced by the presence of Tropical Storm Trami.

At one point, 60 percent of downtown Manila was under water. At least 27 people are known to have died and the cost of damage was estimated at $2.2bn.

The Filipino authorities hope that their preparations will minimise both loss of life and damage to the country’s infrastructure.