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Conditions were ripe for Hurricane Michael's 'rapid intensification'

Warm ocean water and high humidity helped turn Michael into a Category 4 monster.
Hurricane Michael
Hurricane Michael as it approached the Florida panhandle on Oct. 10, 2018.NOAA

When Hurricane Michael slammed into the Florida Panhandle early Wednesday afternoon, it became the most intense hurricane to hit the region in more than 150 years. But if Michael’s path and intensity make it a rarity, so does the speed with which it picked up steam.

Michael spent last weekend churning in the Atlantic Ocean as a tropical storm, strengthening by midday on Monday into a Category 1 storm, with wind speeds of about 75 miles per hour.

But less than two days later, the National Hurricane Center announced that Michael had intensified to a Category 4 storm, with sustained wind speeds of 155 miles per hour.

The hurricane’s fast growth is an example of a phenomenon meteorologists call “rapid intensification,” which the hurricane center defines as an increase in sustained wind speeds of at least 35 miles per hour over the course of a single 24-hour period.

“Storms are known to do this, but normally we see this happening when it’s away from land,” said Corene Matyas, a climatologist at the University of Florida in Gainesville. “What’s unusual is that it’s happening so close to land.”

She said the conditions that jumpstart rapid intensification are typically found over the ocean, where warm waters and moisture in the atmosphere provide the necessary energy to fuel big storms.

“We have really good conditions right now,” Matyas said. “In this case, the surface waters are plenty warm enough, but there were also some instruments dropped from a hurricane hunter aircraft that found warm enough water 300 feet deep to support a hurricane. That’s a lot of energy.”

Another factor that led to Michael’s rapid intensification is the relative absence of strong winds blowing across the storm, according to Matyas. Known as wind shear, such crosswinds disrupt the circulation of moisture within a hurricane and cause its swirling winds to weaken.

Could climate change also help explain intense storms like Michael? It’s possible.

Kevin Reed, an assistant professor of marine and atmospheric sciences at Stony Brook University in New York, said in an email that it was hard to tell whether intense storms like Michael were becoming more common.

But “scientific studies over the last decade suggest that the most intense storms are becoming more intense due to warming of the upper ocean due to climate change,” he said.

Matyas shared that assessment.

“The number of tropical cyclones may stay similar, but the intensity may rise,” she said. “There could be more energy in the atmosphere, and more energy in the ocean, because temperatures are warmer, and then that energy is there just waiting to be unlocked.”

Additional reporting by David Freeman.

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