What Is a Super Typhoon, and Why Are They So Dangerous?

This has been a record-breaking week for global hurricanes as powerful storms struck both the Pacific and Atlantic Ocean basins, leaving scientists wondering whether they’re harbingers of a more destructive climate-warmed future or are outliers that test the limits—but remain within—the realm of normal variability.

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On Sunday, Super Typhoon Goni left a trail of destruction over several smaller Philippine islands, with winds estimated at 195 miles per hour. It was the strongest storm ever to hit land, according to measurements by the National Oceanic and Atmospheric Administration’s National Hurricane Center and the Navy’s Joint Typhoon Warning Center. Luckily, Gomi missed densely-populated Manila and its surroundings. It’s expected to hit Vietnam with heavy rains and lesser winds late Thursday.

And in the Caribbean, the Category 4 Hurricane Eta struck the coast of Nicaragua on Tuesday with 145-mph winds, resulting in “life-threatening storm surge, catastrophic winds, flash flooding, and landslides” across portions of Central America, according to a Tuesday morning advisory by NOAA’s hurricane center. Nicaraguan emergency officials issued an evacuation order for the entire coastline, and the region is expected to be doused with up to 35 inches of rain by Sunday.

Hurricane Eta is the 28th named storm of 2020 in the Atlantic basin, tying the record set in 2005.

The reason that both storms have been so strong and so late is that both the Pacific and Atlantic oceans have stayed warm this year, says John Knaff, a meteorologist at NOAA’s Cooperative Institute for Research in the Atmosphere at Colorado State University. “The Atlantic season is a prototype for what happens when you have very warm sea surface temperatures,” Knaff says. “You have more energy for the storms to become very strong.”

Meteorologically, typhoons and hurricanes are the same phenomenon; it’s just traditional to call them typhoons in the western Pacific or hurricanes in the eastern Pacific or Atlantic. They start as storms that pass over hot surface water, at least 80 degrees Fahrenheit, down to 150 feet deep. These storms suck up water from the ocean’s surface, which evaporates into the air. As they rise, the water vapor condenses to form droplets, releasing more energy, while low pressure beneath the rising air masses brings in a rush of more air. A tropical storm officially turns into a hurricane when these counter­clockwise winds reach 74 miles per hour. Meteorologists applied the “super” designation to Typhoon Goni after it reached wind speeds of 150 miles per hour.

Earlier this year, NOAA officials predicted that 26 named hurricanes would form in the Atlantic, with between three and six categorized as “major,” and academic research teams separately predicted a “hyperactive” hurricane season. So far in 2020, five of the 28 storms have been major ones. “I was skeptical at the beginning of the season in the Atlantic,” Knaff says. “But it’s been pretty spectacular.”

By contrast, NOAA meteorologists predicted a slower-than-normal storm season in the Pacific, and although Super Typhoon Goni was a big one, that forecast has generally proved correct.