Milton’s update: How are hurricanes classified and why isn’t there a category 6?
In just a few hours, Hurricane Milton grew to a Category 5 hurricane on Monday, with wind speeds increasing by a staggering 90 mph in just over a day, a process meteorologists call “rapid strengthening.”
The increase was due to unusually warm ocean waters in the Gulf of Mexico, which is close to record temperatures in 2024. On Tuesday morning, Milton weakened slightly to an “extremely strong” Category 4 storm, but is expected to increase in size. and remains “extremely dangerous” as it approaches Florida Wednesday night, the National Hurricane Center said.
Warm water causes hurricanes by rapidly evaporating, and rising columns of warm, moist air give hurricanes the energy they need to strengthen quickly. This heat played a big part in Milton’s growth, making him very dangerous.
How are hurricanes classified?
The Saffir-Simpson Hurricane Wind Scale is a 1 to 5 rating system based on sustained hurricane wind speeds, used to estimate potential property damage. Here’s a quick summary of the characteristics of each hurricane category. You can find more information about categories on the National Oceanic and Atmospheric Administration (NOAA) website here.
- Category 1 Storm: Winds between 74-95 mph (119-153 km/h) cause some damage to roofs, siding, and power lines, resulting in power outages lasting several days.
- Category 2 Storm: Winds between 96-110 mph (154-177 km/h) cause extensive damage to roofs and trees, with power outages lasting several days to weeks.
- Category 3 Storm: Winds between 111-129 mph (178-208 km/h) cause devastating damage to homes, trees, and infrastructure, as power and water are out for days to weeks.
- Category 4 Storm: Winds between 130-156 mph (209-251 km/h) cause significant damage, with heavy roof and wall damage and widespread outages, leaving areas uninhabitable for weeks or months.
- Category 5 Storm: Winds of 157 mph (252 km/h) or higher cause total roof and wall collapse, tearing apart homes and making them uninhabitable for weeks or months.
Why is there no section 6?
There is no Category 6 storm, because Category 5 is considered the threshold at which additional wind speeds do not significantly increase the likelihood of infrastructure damage, as complete destruction is imminent.
However, a study published earlier this year e Proceedings of the National Academy of Sciences argues that global warming is supercharging some of the strongest hurricanes, making them even more dangerous. The authors suggest that Category 5 may underestimate the risks posed by these storms, especially as rising ocean and atmospheric temperatures contribute to their intensity.
Michael Wehner, the study’s lead author, told CBS News at the time that his team had measured several hurricanes over the years that would have qualified as a hypothetical Category 6, including Typhoon Haiyan in 2013.
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