Tropical Storm Koppu is on track to become a powerful and slow-moving typhoon, putting lives and property across Luzon Island of the Philippines in danger this weekend and early next week.
Koppu is currently a tropical storm churning away from Guam and toward the Philippines. Disruptive wind shear has prevented Koppu from taking advantage of the warm waters of the Pacific and strengthen significantly. That should change by this weekend as Koppu approaches Luzon.
"Rapid intensification is likely to occur right before Koppu reaches Luzon," stated AccuWeather Meteorologist Adam Douty. "Koppu could become a significant typhoon, possibly the equivalent to a Category 4 hurricane."
Koppu will not only strengthen as it approaches the Philippines but will also slow down significantly. The combination of a powerful and slow-moving typhoon could spell a disastrous situation for residents and communities in its path, which will be northern Luzon Island in Koppu's case.
From this weekend into early next week, Koppu will crawl toward or into northern Luzon Island before eventually turning to the north. When Koppu makes that turn to the north will determine if Luzon endures a direct hit or a narrow miss by its center and most destructive winds.
Even if its center never makes landfall, Koppu will still pass close enough to northern Luzon to unleash days of torrential rainfall.
"A total of 300 to 600 mm (12 to 24 inches) of rain is expected to be widespread," stated Douty. There will even be localized amounts upwards or in excess of 900 mm (36 inches). Such rain is sure to trigger severe and life-threatening flooding and mudslides.
"The most significant rain will fall in the mountainous terrain of northern Luzon," added Douty.
Residents in Baguio, Bangui, Aparri, Tuguegarao and Pagudpud are among those across northern Luzon who are being urged to prepare for the impending severe flood danger. Heed all evacuation orders and begin making plans to seek shelter away from areas prone to flooding and mudslides.
Streams and rivers will quickly turn into raging waterways and flood neighboring homes and land, roads and bridges can get cutoff and low-lying communities could get turned into lakes.
Koppu will also bring a threat of damaging winds, coastal flooding and extremely rough seas to northern Luzon.
"Wind damage will be greatest along the northeast coast of Luzon with wind in excess of 160 kph (100 mph) possible," Douty continued. The damaging wind threat will become more expansive and severe across northern Luzon the farther Koppu tracks inland. The potential for winds to knock down trees will only increase as the rain persists and further saturates the soil.
Based on current indications, Koppu will stay far enough to the north for Manila to escape most of the impacts.
Impacts from Koppu will not be limited to the Philippines. Taiwan, Japan and far eastern China remain on alert for potential hazards next week.
"From Monday into Tuesday, we should see Koppu slowly begin to pull to the north and impacts in Taiwan should gradually increase," stated Douty.
How far west Koppu tracks around Luzon before turning to the north will determine whether far eastern China or Japan's southern Ryukyu Islands join Taiwan in facing hazardous weather next week. The eventual track of Koppu could also put more of Japan in its path late in the week.
"Even if Koppu continues to the north into the East China Sea, it will encounter increased wind shear and should significantly weaken," Douty said. "Because of this, if there are impacts to Japan, we do not think they will be significant."
AccuWeather meteorologists will continue to provide updates on the expected track and more precise details of its potential impacts to lives and property in the upcoming days.
Behind Koppu is Champi, which strengthened into a tropical storm in the western Pacific Basin on Wednesday.
Douty expects this system to cross the Northern Mariana Islands on Friday and will either be at or approaching typhoon status.
"Saipan is probably the largest island that will be impacted by this system as it will pass to the north of Guam," he said.
Latest indications point toward this system then curving to the north, then northeast away from Japan next week.