When meteorologists issued their forecasts for Typhoon Surigae on Friday, they knew the Category 2-equivalent storm had the potential to intensify quickly. But by Saturday morning, the storm had exceeded forecasters’ wildest expectations, attaining Category 5 status and practically leaping off the scale.
In fact, such a feat has never occurred in January, February, March or May, either.
According to Jeff Masters, a meteorologist for Yale Climate Connections, only four tropical cyclones reliably measured worldwide have featured higher wind speeds.
Surigae’s rate of intensification was also unprecedented for an April storm, the cyclone’s wind leaping some 105 mph in strength in just 36 hours.
While the system largely spared the Philippines from significant impact, it did spur 75-foot waves over the open northwest Pacific and could influence the North American weather pattern in the next seven to 10 days. Beyond its direct impacts lurks a climate warning: The storm has racked up myriad feats that are expected to become increasingly common in a warming world.
A rapidly intensifying storm
The storm intensified at breakneck speed, fitting into a trend climate scientists have observed in recent decades and expect to continue.
“Rapid intensification is projected to become more probable over the 21st century,” stated a March report from leading scientists investigating the links between climate change and tropical cyclones.
The term “rapid intensification” describes a 35-mph or greater increase in maximum eyewall winds within 24 hours. A record-tying 10 storms rapidly intensified during the 2020 Atlantic hurricane season.
#Surigae strengthened by 90kt (105mph) in the last 36 hours.— Sam Lillo (@splillo) April 17, 2021
There are 64 other TCs on record that have hit this level of rapid intensification.
Here are the dates of those in the northern hemisphere.
Two of them happened miles apart in the Atlantic last year: Delta and Eta pic.twitter.com/l6DTQNKwpV
Surigae’s pace of strengthening doubled the rate needed to qualify for rapid intensification, and its 190-mph peak winds were stronger than Hurricane Dorian, which ravaged the Bahamas at the start of September 2019. The threshold for Category 5 status is 156 mph.
The storm took advantage of sea surface temperatures near 87 degrees and a lack of wind shear, or a change of wind speed and/or direction with height. Wind shear is known to disrupt tropical cyclones and can knock fledgling systems off-kilter.
A hidden warning
Kerry Emanuel, a professor at the MIT, has conducted extensive research and modeling showing a link between a warming climate and the potential for a storm to rapidly intensify.
“We would expect a significant increase in extremes of storm intensification, including those that happen just before landfall,” Emanuel wrote in a 2017 study published by the American Meteorological Society. He also noted that storms intensifying 115 mph or more before landfall — roughly a once-a-century occurrence nowadays — could happen every five or 10 years on average by the end of the century.
Jim Kossin, a climate researcher at the National Oceanic and Atmospheric Administration, told The Washington Post in November: “In the early 1980s, the chance of having a hurricane intensification event of 35 mph or more in a 24-hour period was about 1 in 100. Thirty years later, the chance has gone up by a factor of five to about 1 in 20.”
In October 2019, Typhoon Hagibis intensified from a tropical storm to a Category 5 monster in just 18 hours as it churned through the northwest Pacific, one of the fastest rates of rapid intensification ever observed.
A steamier, more volatile environment for a tropical cyclone
Surigae didn’t only set records for peak wind speed. Its minimum central air pressure, linked to how much air is being drawn into the storm, bottomed out at 888 millibars, according to the Joint Typhoon Warning Center. That’s the air pressure one would find at a height of 2½ times that of the World Trade Center, since air pressure decreases with height. That deficit of air had a vacuum effect and fueled the extreme winds spiraling into Surigae. It beats the previous air pressure record for a storm so early in the year by 1.5 percent.
Climate scientists have long been predicting an uptick in the proportion of high-end tropical systems in a world affected by climate change. That’s because the environment is becoming increasingly favorable for high-end storms, effectively raising the ceiling of just how bad they can get.
The potential intensity, or theoretical upper bound of strength, of a storm is proportional to the difference between sea surface temperatures and air temperatures high in the atmosphere. Sea-surface and upper-atmospheric temperatures are increasing somewhat in tandem, balancing out and having little impact on potential intensity.
However, potential intensity is also correlated with how much energy is contained in air above the sea surface thanks to its temperature and humidity. That value is increasing in a world warmed by human-induced climate change, accounting in part for the link between a warming climate and an uptick in the frequency of high-end storms. It’s expected that the future will hold more high-end hurricanes and typhoons, since the environment can support stronger storms.
It’s not just a theory. A pronounced shift toward more-intense storms has already been noted globally, especially in the Atlantic in recent years. “The global average proportion of intense TC [tropical cyclone] occurrence … has increased since 1979,” the March report on tropical cyclones and climate change said, referring to storms Category 3 or higher.
The Atlantic Basin has recorded seven Category 5 hurricanes in the past five years, a number never recorded previously. They are also occurring not only at unusual times but in unusual places: In September 2019, Hurricane Lorenzo reached Category 5 status farther northeast than any other hurricane on record in the basin. It claimed that record by an incredible margin, reaching Category 5 strength about 600 miles farther east than Isabel and Hugo.
Experts have predicted another active Atlantic hurricane season this year.
Meanwhile, Surigae on Monday was a low-end Category 4-equivalent “annular” typhoon, meaning its eye had widened and was surrounded by one solid region of strong winds and rain. It’s expected to gradually weaken as it drifts through the open Pacific east of Japan.
Jason Samenow contributed to this report.