Science

How hurricanes like Michael form

how hurricane forms infographic
Shayanne Gal/Business Insider
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The bands of Hurricane Michael, a major Category 4 storm, are hitting the Gulf Coast of Florida. Its eye is expected to make landfall imminently, and Michael could be the most destructive storm to hit Florida's Panhandle in decades. 

"THIS IS A WORST CASE SCENARIO for the Florida Panhandle!! Listen to your local emergency officials. Stay Inside & Survive!" NWS Director Dr. Louis Uccellini tweeted Wednesday

Given its extremely low central pressure — 923 mb as of 11 a.m. — Michael could be one of the strongest hurricanes ever to hit the US. (Hurricane Andrew's was 922 mb and Katrina's was 920 mb.)

Hurricanes are vast, low-pressure tropical cyclones with wind speeds over 74 mph.

In the Atlantic Ocean, the hurricane season generally runs from June 1 through November, with the peak of storm activity occurring around September 10. The storms form over warm ocean water near the equator, when sea surface temperature is at least 80 degrees, according to The National Hurricane Center

As warm moisture rises, it releases energy, forming thunderstorms. As more thunderstorms are created, the winds spiral upward and outward, creating a vortex. Clouds then form in the upper atmosphere as the warm air condenses.

As the winds churn, an area of low pressure forms over the the ocean's surface. At this point, hurricanes need low wind shear — or a lack of prevailing wind — to form the cyclonic shape associated with a hurricane. Once the wind speed hits 74 mph, the storm is considered a Category 1 hurricane on the Saffir-Simpson scale. 

saffir simpson hurricane scale
Samantha Lee/Business Insider

Hurricanes use warm water as fuel, sucking up moisture and expanding outward. But when the storm moves over colder water or land, it dissipates.

Because climate change is causing ocean and air temperatures to climb, hurricanes are getting stronger, wetter, and more sluggish.

Recent research from the National Oceanic and Atmospheric Administration found that storms slowed by an average of 10% between 1949 and 2016, making storm surges and the associated flooding more costly and disastrous. On top of all this, sea-level rise also increases the flood risk from hurricanes.

Although it remains to be seen how Hurricane Michael will play out in the US, the storm killed at least 13 people in Central America after its torrential downpours caused flash flooding, according to Reuters.

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Jeremy is the founder and editor-in-chief of Cultivated Media, a newsletter bringing readers inside the emerging cannabis industry. Beyond his reporting, Jeremy is studying for his MBA at Columbia Business School and holds a certificate in cannabis pharmacology from the University of Vermont where he studied as a cannabis media fellow. Jeremy was formerly a senior reporter at Insider where he focused on the cannabis industryJeremy has covered the bumpy rollout of Canada's cannabis legalization, the boom in cannabis companies going public (and the resulting fallout), multibillion-dollar mergers between cannabis companies and corporations from other industries, the ongoing health effects from vaporizers, the mislabeling of CBD products, and how the world's largest financial, legal, and political institutions are reacting to and planning for legalization. He has also gotten scoops and broken news on layoffs affecting cannabis companies, startups raising money, banks and law firms building specialized cannabis practices, tracked which companies and individuals are profiting from cannabis, and profiled some of the top executives, investors, and leaders in the industry.He is a sought-after expert on cannabis business and policy, frequently speaking to the media and at industry conferences.
Shayanne Gal was a Senior Data Graphics Designer at Insider.