Super Typhoon Brings Torrential Rains to Taiwan

The heavy rains and whipping winds from Super Typhoon Nepartak are pummeling Taiwan. While the island’s residents have hunkered down, with almost every city and county closed, there are still risks of significant flooding from the storm.

After it passes over Taiwan, Nepartak — the strongest storm to form in the Northern Hemisphere so far this year — will dump rain on eastern China, parts of which are already experiencing destructive flooding from seasonal rains.

Super Typhoon Nepartak as it headed toward Taiwan on July 6, 2016.

Credit: NASA

Nepartak formed on July 3, ending a record-long lull in tropical cyclone activity for the northwest Pacific Ocean basin. Thanks to abundant warm ocean waters and favorable atmospheric conditions, the storm rapidly intensified.

It is now a super typhoon with sustained winds estimated at about 150 mph, the equivalent of a strong Category 4 hurricane on the Saffir-Simpson scale. (Hurricanes and typhoons are different names for the same phenomenon.)

A buoy fortuitously recorded the passage of Nepartak’s eye, and measured its central pressure (a mark of its intensity) and wind speeds of more than 170 mph.

“Getting any [tropical cyclone] eye to pass over a buoy is a stroke of really good luck, so it’s notable just because it happened,” Brian McNoldy, a hurricane researcher at the University of Miami, said in an email. The fact that it was such a strong storm means it’s “certainly an impressive measurement,” he said.

It’s not unusual to have such strong storms in this region; the northwest Pacific on the whole is the busiest ocean basin for tropical cyclones and regularly produces ones on the higher end of the scale.

Since 1950, Taiwan has been hit by 25 typhoons of Category 4 or 5 strength, hurricane expert Phil Klotzbach of Colorado State University, said in an email.

As with any tropical cyclone, there are concerns over damage caused by ferocious winds, torrential rains and pounding storm surge.

Wind damage is mitigated by the strict building codes enforced in the country, according to catastrophe risk modeler AIR Worldwide.

“Taiwan is generally pretty well-equipped to handle the wind from intense typhoons, but the rain is always a troublemaker because of the terrain,” McNoldy said. “That’s not to say that a storm of this intensity won’t cause wind-related damage, but less than what we’d probably assume based on our coastal cities.”

Downpours are the primary concern because the island’s rugged mountains wring more rain out of storms: As the moisture-laden air is forced up by the peaks, it cools and forms copious amounts of precipitation.

Previous storms have wrought considerable destruction from flooding. In 2009, Typhoon Morakot dumped more than 24 inches of rain across much of the southern part of the island, and up to 40 inches on the worst-hit places. More than 500 people were killed by mudslides and flooding and billions of dollars in damage were caused.

Heavy rains with storms, whether thunderstorms or tropical cyclones, have been made more likely thanks to the warming of Earth’s atmosphere. A warmer atmosphere contains more moisture, which means more is available to fall as rain. Ocean warming is also expected to result in more intense typhoons.

Taiwan’s mountains will shred and weaken Nepartak before it emerges over the Taiwan Strait and then likely makes a second landfall in China.

There are flooding concerns there, too, because even though it will be weaker, Nepartak will still be able to drop considerable rains. Parts of China are already reeling from flooding caused by seasonal rains that have left the Yangtze River swollen and sent torrents streaming down city streets.

“If Nepartak were to directly come ashore in eastern China — or merely glance the region — it will unquestionably bring even more rainfall to some of the hardest-hit areas along the Yangtze River basin in Anhui, Hubei, and Jiangxi provinces,” Steve Bowen, a meteorologist with the reinsurance firm Aon Benfield, said in an email.

The typhoon’s exact track after landfall is still somewhat uncertain, though it looks to at least glance China.

“It’s going to be a really nervous next 48 to 72 hours for residents in China and Taiwan when the damage from Nepartak fully comes to light,” Bowen said.