How Hurricane Matthew surprised everyone and became a catastrophic storm

Hurricane Matthew is roaring northward after devastating Haiti earlier this week. The Category 4 storm was the strongest hurricane to hit the impoverished island nation in more than 50 years, and the death count continues to rise. Now, it’s on its way to Florida.

"This is a disaster."

The National Hurricane Center cautions that Hurricane Matthew could cause catastrophic damage if it hits Florida. "A major hurricane has not impacted this area in 118 years, since October 2nd 1898. There is NO local living memory of the potential of this event," warns the National Weather Service in Jacksonville, Florida in a briefing.

It’s not yet clear what path the storm will take. So far, Matthew hasn’t made landfall in Florida and as of 5PM ET it’s about 100 miles away from West Palm Beach. It’s possible that the storm could skirt Florida’s eastern coastline and stay offshore. But if the storm’s track moves a little to the left, there will be devastating wind impacts, structural damage, and giant waves surging along the coastline. Both mandatory and voluntary evacuations have been issued to get people out of danger in Florida, Georgia, and the Carolinas, according to The Weather Channel.

US Navy

The hurricane’s fury was largely unexpected when it began as a tropical storm over the Windward islands on September 28th. That’s because forecasters thought that Matthew didn’t have all the ingredients to become a massive hurricane when it started stirring, says hurricane researcher Nick Shay at the University of Miami in Florida. Usually, warm ocean waters and atmospheric disturbances traveling west from Africa create what amounts to an atmospheric exhaust fan: warm, moist air evaporates off the surface of the ocean and rises to cooler altitudes. The low pressure this creates sucks more warm air into the exhaust fan — driving the formation of massive rain clouds and spinning winds.

Devastating wind impacts, structural damage, and giant waves

That is, as long as there aren’t already high-altitude winds to blow it apart. If you draw a vertical line from the ocean’s surface through our atmosphere, the different directions and speeds of wind along that line are called the wind shear. The wind shear measured where Matthew developed and made forecasters think it might not pick up enough speed to become a major storm, Shay says.

"All of our tools were suggesting a hurricane, but not a strong hurricane," says Chris Landsea, the science and operations officer for the National Hurricane Center. And Matthew started out small. But over 24 hours, it grew in strength. "We had no clue that it was going to become Category 5, or a Category 4." Both categories mean catastrophic damage that leaves some regions uninhabitable (the wind speeds of a Category 5 storm reach more than 157 miles per hour).

NASA

Matthew was a Category 4 when it hit Haiti. Winds at speeds up to 145 miles per hour tore through the country and torrential rains pummeled it, according to The New York Times. At least 100 people have died, the New York Times reports. Regions of Haiti have been inaccessible and unreachable by phone because the storm. United Nations officials report that more than 15,000 people have been displaced and as many as 350,000 need help. "One of the really peculiar things with this storm, in and of itself, is the fact that most storms, when they reach severe status like Category 4, they don’t remain Category 4 for nearly as long as Matthew did," Shay says.

Deep, warm pockets of water fuel hurricanes. So when they pass over cooler spots, or especially land, they usually lose speed. That’s especially true for mountainous regions, says Kristen Corbosiero, a hurricane researcher at State University of New York in Albany. Mountains slow the low, fast, swirling winds with friction as well as by interfering with their circulation.

The hurricane’s fury was largely unexpected

But even after it traveled across the mountains of Haiti and Cuba, Matthew’s speed only dipped to a Category 3 — which means wind speeds of up to 129 miles per hour. That’s enough to uproot and snap trees. Such a storm can still create flash floods, mudslides, and storm surges which The National Hurricane Center warns are life-threatening.

Now, as the hurricane’s eye sets its sights on the city of Freeport in the Bahamas, winds are reaching 140 miles per hour. The eastern coast of Florida is next, and the National Hurricane Service has extended its hurricane warning as far north as South Carolina.

Florida might not prove much of an impediment to the hurricane’s speed: the state is basically sea level, it’s warm, and it’s humid, Those are hurricane-friendly conditions, and are unlikely to slow it much.

"From a scientific perspective, when you look at this, you say ‘Wow, Mother Nature has really created this masterpiece,’" Shay says. "But on the other hand, for John and Jane Q Public, this is a disaster."