Why this deviant, looping typhoon is stunning meteorologists

Typhoon Gaemi, a powerful Pacific storm, is blasting Taiwan after tracing a bizarre loop-de-loop that has bewildered meteorologists and had disastrous consequences for the country’s residents and infrastructure.

Meteorologists expressed astonishment on social media as they watched the typhoon — equivalent in strength to a Category 3 hurricane — take an improbable and perplexing path that meant Taiwan’s east coast was hammered by the storm’s intense inner core twice.

The storm’s unusual track was described as “absolutely wild,” “ludicrous” and “crazy.”

Heavy rain inundated parts of Taiwan’s southern city of Kaohsiung, after Typhoon Gaemi made landfall on the island July 25. (Video: Reuters)

The storm, which is producing sustained winds of 125 mph and gusts to 155 mph, recently attempted landfall for the second time — in roughly the same zone that it narrowly missed hours earlier.

As a result, coastal parts of eastern and particularly northeast Taiwan have been subjected to a protracted period of severe to extreme winds, a perilous ocean surge and torrential rains — which are expected to cause flash flooding and mudslides in the higher terrain.

A full loop

Tropical cyclones (hurricanes, typhoons, etc.) are prone to wobbling sometimes; like a spinning top, they sometimes jog left or right. Meteorologists call these “trochoidal wobbles.” But this isn’t what Gaemi did.

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Instead, Gaemi charged westward toward the coast with its ferocious eyewall, the zone of violent winds surrounding its calm center, lashing the shoreline. Then it made a hard left turn, banked south, then curved east and eventually north, tracing a full counterclockwise loop. Then it weakened before heading inland in northeast Taiwan.

Getting a hurricane to change direction is an enormous feat; imagine a freight train trying to slow down. A hurricane will only change direction if the overarching steering currents change or something prompts a restructuring of its inner core.

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In this instance, Gaemi was running into mountainous terrain. The Chungyang Range and the Xueshan Mountains both reach 10,000 feet or higher in northern Taiwan.

According to research, the mountains have the effect of deflecting an incoming storm southward initially before it rebounds to the north.

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Interestingly, an artificial intelligence model simulated the possibility of this sort of motion as early as several days ago.

There is precedent for this type of deviant motion to occur as storms approach Taiwan. A 2018 study found that, of 84 landfalling tropical cyclones, seven traced full loops offshore of Taiwan. A total of 49 experienced some leftward motion, and 18 had a large deflection to the left.

Gaemi’s impact

Gaemi rapidly intensified from a Category 1 to a Category 4 storm overnight Tuesday into Wednesday local time, peaking with winds around 150 mph.

As of 12:30 a.m. local time Wednesday, the eye — slightly degraded and weaker than it was at peak Category 4 intensity earlier — was moving ashore between Xiulin and Nan’ao, affecting Yulin County. In the mountains, Taiwan’s Central Weather Administration hoisted extremely torrential rain advisories, with torrential rain advisories in effect for much of the country’s coastal lowlands. The entirety of Taiwan is under a land typhoon warning.

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Where the eye is moving ashore, winds may gust 100 to 120 mph at the immediate coastline and in the higher terrain. Several feet of rain are expected in the mountains. Taipei, which is in the storm’s northern eyewall, will likely experience 75 to 95 mph gusts, with a foot of rain possible too.

Social media video showed the storm knocking people off their feet, and unleashing flying debris and blinding sheets of rain. Initial measurements indicated some mountainous areas had received at least three feet of rain.

Jason Samenow contributed to this report.

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