Typhoon Koppu will put lives and property across Luzon Island of the Philippines in danger through early next week.
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Koppu developed into a typhoon early Friday morning local time and is currently approaching the northern Philippines. Disruptive wind shear had prevented Koppu from any significant strengthening through Thursday; however, Koppu will enter an area of low wind shear prior to making landfall in Luzon. This will allow for continued strengthening and result in Koppu becoming a very dangerous cyclone as it approaches and moves into Luzon this weekend.

"Rapid intensification is likely to occur right before Koppu reaches Luzon," stated AccuWeather Meteorologist Adam Douty. "Koppu will be the equivalent of a Category 4 hurricane by landfall."

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 and into northern Luzon Island before eventually turning to the north. Koppu is expected to make landfall, but how quickly it turns north will determine the duration of life-threatening conditions for northern Luzon.
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© NOAA/Satellite
This animated GIF shows Koppu approaching the northern Philippines.
While damaging winds are a concern, the greatest threat will be life-threatening flooding from 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 cut off and low-lying communities could get turned into lakes.

While dangerous flooding is the primary concern, 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 200 km/h (125 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 the worst of the impacts; however, heavy rain may push into the city and surrounding areas on Sunday afternoon into Monday. During this time there will be a heightened risk for flash flooding.

Impacts from Koppu will not be limited to the Philippines. Taiwan, Japan and far eastern China remain on alert for potential hazards next week.

"By Tuesday, we should see Koppu slowly begin to pull to the north and impacts in Taiwan should gradually increase," stated Douty.

How long Koppu tracks over Luzon and stalls 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.
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The faster that Koppu shifts northward, the more likely it is that the storm will cross near or east of Taiwan and then be pulled northeast with heavy rain and strong winds possible for the Ryukyu Islands, however mainland Japan would be spared any significant impacts.

The longer Koppu sits over Luzon, the more time high pressure will have to build north of the cyclone producing more of a easterly component to the steering flow which would then likely lead to the cyclone tracking somewhere between Hong Kong and Taiwan during the second half of next week.

This scenario would bring the greatest threats to southern and western Taiwan as well as the east coast of China. While Koppu would likely be a much weaker storm than when it impacts the Philippines, locally damaging winds and flooding rainfall will still be a serious risk.

"If Koppu instead continues to the north past Taiwan and 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 typhoon in the western Pacific Basin on Friday.

Champi crossed the Northern Mariana Islands on Friday with wind gusts around 130 km/h (80 mph).

While Saipan was battered by Champi, Guam was far enough south to miss the worst of the cyclone. Even so, wind gusts of 65-80 km/h (40-50 mph) were common along with downpours.

The latest indications point toward this system then curving to the north, then northeast well away from Japan.

Content contributed by AccuWeather Senior Meteorologist Kristina Pydynowski