Using One Typhoon to Predict Another

July 13, 2016

Last week Typhoon Nepartak caused tremendous damage in Taiwan and, nearly two days later, in China’s Fujian province. At least three people were killed in Taiwan and nine in China, with several others missing and more than 400,000 evacuated. Both countries experienced power outages and major disruptions to air and rail service because of the storm. In China, a landslide triggered by the heavy rains temporarily trapped 18 factory workers.

It could have been even more deadly, however; evacuations got many people out of harm’s way, and in addition the storm weakened as it moved toward Taiwan and again as it crossed the Taiwan Strait toward China’s eastern coast over the weekend. It had started as a Category 5 “super typhoon,” was classified as Category 4 when it reached Taiwan on Friday morning, and was significantly weaker by the time it reached China’s coast on Saturday.

For the record, Taiwan has experienced 19 storms of Category 4 or higher since 1971. This one left up to 2 feet of rain in the southeastern part of the country.

Fortunately, we’ve gotten better at predicting such storms’ movement and intensity. This article from Stormwater details research carried out about three years ago in Taiwan and the US. Scientists carefully studied another storm, 2009’s Typhoon Morakot, which brought nearly 10 feet of rain to some parts of Taiwan in a 72-hour period. The storm killed hundreds of people and was far worse than meteorologists at the time had predicted. The article describes how researchers several years later ran computer simulations of the typhoon and used them to calibrate and test various modeling programs. Using data from Morakot and running repeated simulations, they were able to predict where individual clouds might form, how much moisture they were likely to carry, and even where they would release that moisture. In mountainous terrain like Taiwan’s this is especially important for knowing where to plan evacuation routes and provide other emergency measures.

Despite the best predictions and massive evacuations, though, models can’t prevent storms from doing damage. We hope the recovery goes smoothly for all those who were affected. You can see photos here of some of the damage in Taiwan; scroll to the bottom of the page.

About the Author

Janice Kaspersen

Janice Kaspersen is the former editor of Erosion Control and Stormwater magazines.