Hurricane John grew from a tropical storm to a Category 1 hurricane on Monday afternoon as it churned off the southwestern coast of Mexico. Maximum sustained wind speeds reached 85 miles per hour, threatening the small tourist town of Puerto Escondido, known for its laid-back, surfing vibe.
Pacific disturbances like this one typically form between July and September, according to Matthew Rosencrans, the National Oceanic and Atmospheric Administration’s lead meteorologist for the seasonal hurricane outlook. Such storms can cause catastrophic damage in the region.
Key things to know about the storm.
The storm could still intensify. Hurricane John is forecast to continue its rapid intensification into a major hurricane, meaning at least a Category 3, as it makes landfall early Tuesday morning in the Mexican State of Oaxaca. A portion of the coastline is currently under a hurricane warning, according to NOAA.
Residents should get ready for heavy rains. Forecasters are also predicting nearly 30 inches of rain along the coastline. Heavy rains could cause catastrophic flash flooding and mudslides in Oaxaca, along with the Mexican states of Chiapas and Guerrero. Other regions could see 6 to 12 inches of rain through Thursday that could cause life-threatening flood risks, especially near the coast.
A recent study showed that rapid intensification like what John is expected to undergo is now twice as likely, at least for Atlantic hurricanes, partially because of human-caused climate change driven by the burning of fossil fuels. Earlier this year, Hurricane Beryl broke records when it became the earliest hurricane ever to reach Category 4 and then Category 5 intensity in the Atlantic Basin, with wind speeds increasing by 35 miles per hour or more within a 24-hour period.
Even if Hurricane John doesn’t continue to grow in strength, it is still likely to bring damaging hurricane-force winds above 74 miles per hour and dangerous storm surge, or an unusually high rise in sea level and wave height that could cause flooding.
Hurricanes are also unleashing higher levels of rainfall as global temperatures increase.
Carrie Stevenson, a faculty member at the University of Florida who works with local communities on hurricane preparedness, said the rainfall forecast could be devastating.
“It’s going to be a really big rainmaker,” Ms. Stevenson said. “Flash flooding could be the most dangerous part of this.”
She’s also concerned that if the storm is strong enough it could cross Mexico and emerge in the Gulf of Mexico, near where a storm currently known as Potential Tropical Cyclone Nine is expected to move north this week.
“I’d definitely watch that because it’s not on the radar of anyone in the Gulf of Mexico,” Ms. Stevenson said.
How La Niña is affecting the Eastern Pacific storm season.
NOAA predicted 11 to 17 named storms for the Eastern Pacific, said NOAA’s Mr. Rosencrans; Hurricane John makes 10.
The season’s scope could be shaped by the natural climate pattern of a waning of El Niño that led to ENSO-neutral conditions that lasted through the summer before sliding toward La Niña conditions that are more favorable to the formation of Atlantic hurricanes. NOAA has issued a La Niña watch.
“On a weekly basis we’re there,” said Mr. Rosencrans of La Niña, adding that sea surface temperatures hit the qualifying mark this week. But since La Niña values can fluctuate, the climatic state is measured on a monthly or seasonal basis, so forecasters at NOAA have not yet officially declared the change.
Mr. Rosencrans expected La Niña conditions to continue forming between September and November. “It’s not like it starts one day, but more like you morph into it,” he said.
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