For the second time in as many months, we’re dealing with “twin typhoons” out in the western Pacific Ocean, and the stronger of the two is on a collision course with the Philippines. The typhoon is moving slowly, and the models don’t paint a pretty picture for the northern half of the country as it passes through over the next couple of days.

Typhoon Koppu, which is known locally in the Philippines as “Typhoon Lando” due to a quirk in naming conventions, is predicted to strengthen into a powerful tropical cyclone as is slowly makes its way toward Luzon, which is the large island that makes up the northern part of the country.

The predicted strength of the storm is alarming in normal situations, but the big story with Koppu will be unbelievable amounts of rain that are likely going to fall over the next couple of days.

The latest forecast from the Joint Typhoon Warning Center shows Koppu making landfall on Luzon around midnight on Sunday with winds of about 130 MPH, making it the equivalent of a category four hurricane on the Saffir-Simpson Hurricane Wind Scale. (For reference, Manila is 12 hours ahead of Eastern Daylight Time.)

After landfall, Koppu will very slowly traverse Luzon until it reemerges over open water sometime on Tuesday. That’s an incredibly long time for a tropical cyclone to sit and spin over rough terrain, and the models are showing a catastrophic amount of rain as a result.

Manila, the capital of the Philippines and the center of a metropolitan area that’s home to tens of millions of people, is located on Luzon but should escape the worst of the storm. However, its millions of residents are still at risk of experiencing strong winds and flooding rains as Koppu skirts the metro area. Any southward jog in Koppu’s eventual track will lead to a much more serious situation for Manila and surrounding areas.

The predicted rainfall across Luzon breaks the scale on most websites that generate images from the GFS (American) weather model, with two feet of accumulated precipitation usually the upper limit on most scales.

Ryan Maue over at WeatherBELL—one of the best follows on Twitter for weather geekiness, by the way—posted a graphic to his feed showing gridded rainfall totals (in inches) from this morning’s run of the GFS.

It’s a bit hard to read, but the colors that approach shades of Barney represent more than two feet of rain, and the hot pink bullseyes show potential rainfall totals of 40-60 inches (!!) by next Friday. Even if this is overdone, that’s a hell of a lot of rain. Rain a fraction of that intensity would be a disaster in most regions (see: South Carolina), so multiple feet of rain falling on Luzon in a few days will create a natural disaster the likes of which the Philippines hasn’t experienced in several years.

And all of that is just from the rain, not including the impact of the storm surge and wind damage that will accompany what is expected to be a category four typhoon crashing ashore. Koppu has all the makings of a complex disaster that will shape the lives of many Filipinos for months and years to come.

The interior parts of Luzon are among the least populated swaths of land in the Philippines, but many people live in villages in the mountains, and there are quite a few densely-populated cities along Luzon’s western coast. Even though the worst of Koppu is predicted to miss the Manila metro, there are still a lot of people in the path of this storm and the catastrophic flooding and mudslides that are soon to unfold.

It’s been a rough typhoon season in the Pacific Ocean this year, with the central Pacific (around Hawaii) recording a record number of storms, and a string of storms in the western Pacific constantly threatening land or making landfall. In the past couple of months, we’ve seen storms like Dolphin, Goni, Soudelor, and Dujuan make landfall, with Taiwan consistently the hardest hit. Koppu could very well threaten Taiwan if it survives its encounter with Luzon, with heavy rain posing the greatest threat along the eastern slopes of the mountains that extend the length of the island.

If you were wondering why this typhoon has two names, the Philippines’ weather bureau—PAGASA—assigned named to tropical cyclones long before there was an international standard for naming. Due to this longstanding tradition, storms that approach the country these days have two names: an official international name (Koppu) and a name assigned by PAGASA (Lando). It can be confusing for us outsiders, but it seems to work just fine for folks in the Philippines, so who are we to judge?

[Top Image: Google Earth | Map of Philippines: Google Maps | Koppu Forecast: JTWC | Model Rainfall Graphic: Tropical Tidbits]

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