Rain still expected to come from Typhoon Koppu could dwarf what has already fallen.

Typhoon Koppu, known locally as “Lando”, remains a typhoon, after crossing Luzon from east to west, from Baler Bay to Baguio. It is now a Category 1 typhoon on the five stage Saffir-Simpson scale and has turned north.

With little to guide its course, it looks as though Koppu will wander up the western side of Luzon, following the coast of the region of Ilocos, for the next two days.

The projected track of Koppu is close to a worst-case scenario for catastrophic rainfall across northern Luzon, home to more than 10 million people.

With a constant supply of moisture from the South China Sea, Koppu is forecast to dump calamitous amounts of rain on Luzon, especially over the regions of Ilocos and Cordillera, causing untold damage.

Even a tropical depression can produce enormous rains if it’s moving slowly, especially when positioned near high terrain: Koppu would maintain at least tropical storm strength if the centre remains just offshore, as seems likely.

Estimates from storm forecast models have been consistent in threatening a five day total in excess of 700mm of rain. This is the forecast for Ilocos and Cordillera; given the mountainous nature of the geography, some places can expect 1300mm, yes, 1.3m of rain.

Baguio, the regional capital of Ilocos, a city with over 300,000 residents, sits at an elevation of roughly 1,500m, but is only 30km from the coast. Baguio is highly vulnerable to moist onshore winds being forced upslope.

The wind is blowing currently at 30 to 50km/h from the SSW, and it has been raining in Baguio non-stop since 09:00 GMT on Saturday. The officially recorded rain collection so far is over 450mm.

It’s doubtful that anyone will remember, but folk memory may recall Baguio’s wettest event ever recorded: In 1911, a typhoon dumped over two metres of rain in less than four days. History does not readily recount the human or financial cost.

It is notable that the city is named after the Tagalog word for hurricane. Tagalog is the root of one of the national languages and a hurricane is just another name for a typhoon.

The republic is now well versed in disaster management and has set up the National Disaster Risk and Reduction Management Council. Nevertheless, Koppu will leave widespread flooding and mudslides, and major agricultural damage can be expected. It will be a monumental task to deal with such devastation.