Rapid intensification: Why hurricanes blow up to monster storms so quickly

Wednesday morning view of Cat 4 Hurricane Michael with vis imagery from NOAA's GOES-16.
Wednesday morning view of Cat 4 Hurricane Michael with vis imagery from NOAA's GOES-16. (NOAA via CNN)

It seems to take forever for some storms to develop into hurricanes while others blow up into a major hurricane within a few hours. The reason for this is a process known as rapid intensification.

According to the National Hurricane Center, rapid intensification happens when there is an increase in the maximum sustained winds of a tropical cyclone of 35 mph within 24 hours.
Rapid intensification happened during Hurricanes Harvey, Irma, Jose, Maria, Florence, and most recently, Michael.

“It basically means a much bigger, stronger storm, that’s going to be harder to weaken significantly before it arrives," said Justin Gibbs, a meteorologist instructor with the National Weather Service Warning Decision Training Division.

Rapid intensification doesn’t always happen. The conditions a storm moves in and out of and how it interacts with those conditions makes or breaks the level of intensification.

The conditions for Hurricane Michael were perfect in the Gulf of Mexico with plenty of warm water to fuel the storm and weakening upper level shear, known as crosswinds, which prevented the hurricane from breaking down.

The timeline for Michael was intense. Here’s how it went down. The system became a tropical depression the first weekend of October. By that Monday, it was a Category 1 hurricane. In under two days, Michael’s intensity blew up to Category 4, or major hurricane status.

Like Gibbs mentioned, it was hard for Michael to weaken before making landfall. In fact, it kept strengthening, coming in just 2 mph shy of a Category 5 status.
Current forecast models are improving to determine the possibility for a hurricane to rapidly intensify, and forecasters at the National Hurricane Center correctly predicted Michael would do just that.

Every system is different. Gibbs mentioned a tropical system can alter the environment around it, “A stronger storm, while not impervious to outside influence, has a little more control of its own destiny, which is a bear to model and predict.”
Gibbs said meteorologists are getting a better understanding of the processes which leads to better forecasting in the future. He recalls Hurricane Florence as, "one of our best examples of combining human forecast ability with improving computer guidance to accurately forecast rapid intensification with a couple days of lead time."
The takeaway: Tropical systems are ever-changing in a very chaotic atmosphere. Keeping up with the tracks and being prepared is the best way to ensure you stay safe whether the storm rapidly intensifies or not. Gibbs agrees that being prepared is key. “Hopefully everyone will heed the warnings and get out of the way as needed," he said.

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