You may have heard in the news that a very powerful hurricane named Matthew has reached the state of Florida this morning. Earlier in the week, it hit the Caribbean countries of Haiti, Cuba, Jamaica, and the Bahamas. Though the storm has veered just off shore and has weakened slightly, Matthew is still expected to cause a lot of damage and flooding in the states of Florida, as well as South and North Carolina. Let's look at how these storms form and why they're so dangerous.
As big as they get
Hurricanes are the largest storms on earth. They can only form over the open ocean. They are also known as cyclones, when they form in the Indian and South Pacific Oceans, and typhoons, when they form over the northwestern Pacific. But despite the different names, they are the same type of storm (we'll stick to using hurricane, as that is the type of storm happening right now).
A hurricane can be well over 1000 kilometres across (about 600 miles). That's almost as wide as the entire state of Texas. The winds in a hurricane can reach 200 km/h (120 mph) and higher. The storm also brings heavy rainfall. Because hurricanes can vary in size and strength, there is a system to measure them. It goes from Category 1, which is the weakest hurricane, to Category 5, the strongest. Hurricanes don't always stay the same size and strength — Matthew was a Category 4 hurricane when it hit Haiti and Cuba, but it is currently a Category 3 (this is still a very powerful storm, though).
Warm water, rising air
We mentioned that hurricanes form over the ocean. Specifically, they form over very warm water (80°F and above). That warm water is what gives the storm energy — turning it from an average thunderstorm into a tropical storm, and finally, a hurricane. The warm water heats the air above it, making this air rise. Because it rises quickly, the cooler air above must get out of the way. It falls quickly outward away from the centre of the storm. All of this quickly rising and falling air begins to gain speed and force, making the storm grow and spin. This helpful video explains even how these storms start and grow.
Heed the warnings
A hurricane is extremely dangerous. Its wind can remove a roof from a home or toss cars down the street. And as the storm reaches land (or makes landfall), it brings with it the "storm surge". These are high waters lifted up by the centre of the storm that cause deep flooding. In many cases, this flooding is the most damaging part of the storm. Even if a structure is strong enough to stand up to high winds, water has a way of getting into buildings and destroying valuables, foundations, and cutting off power for days or even weeks.
In the end, we can be glad that modern science at least allows meteorologists (weather scientists) to predict, observe, and track hurricanes. Sure, we can't stop hurricanes from happening — but we can get enough warning to evacuate areas, save precious possessions, and seek shelter. Right now, citizens across the coast of the southeastern United States are safer because their governments and rescue services are ready. Matthew will damage homes and property. But as the saying goes, these things can be rebuilt — what matters more are that people's lives are saved thanks to our ability to understand how and where hurricanes form.