Hurricanes are dangerous storms that affect millions of people each year.
But what are hurricanes and how do they form? In this video lesson you’ll learn about where and how hurricanes develop as well as the types of hurricanes that are possible.
What Is a Hurricane?
Even if you don’t live in an area where hurricanes hit, you probably know what this image is. Hurricanes have caused a lot of devastation and destruction.
You can likely name some recent hurricanes in the U.S. that did major damage and killed many people: Hurricane Katrina in 2005, Hurricane Irene in 2011 and Superstorm Sandy in 2012 are just a few.
Hurricanes don’t develop out of thin air, though; they begin as small storms that grow into larger, more dangerous ones. In its infancy, a hurricane starts as a tropical depression, which is a tropical spinning storm with wind speeds less than 39 mph. As it grows into adolescence, the tropical depression develops into a tropical storm, which is a tropical spinning storm with wind speeds between 40 and 73 mph. If it develops into a full adult storm, it becomes a hurricane, which is a tropical spinning storm with wind speeds above 74 mph.
After becoming a hurricane, the storm is further categorized as a 1, 2, 3, 4 or 5, increasing with danger and damage as the number increases. A category 1 storm is the weakest hurricane, with wind speeds of 74 – 95 mph. On the opposite end, a category 5 hurricane is a very strong storm. Category 5 hurricanes are very dangerous and do extensive damage. These storms have wind speeds of 155 mph and more.
Hurricane Andrew in 1992 was a category 5 hurricane. It’s important to remember that all hurricanes, even category 1 hurricanes, can be dangerous and damaging.
How a Hurricane Forms
Hurricanes follow the path of least resistance, which is why they travel west across the Atlantic and also why hurricanes rarely hit the West Coast of the United States. The tropical winds blowing across the Atlantic blow from east to west, originating in Africa and then moving toward the Caribbean, Mexico and Southeast U.S.
There’s also a reason why Oklahoma doesn’t get hit by hurricanes but Florida does. Hurricanes only develop over oceans and tend to dissipate once they hit land.Over the tropical ocean regions, warm, moist air rises straight upward, which creates thunderstorms. The water from the air cools and condenses, eventually falling back to land as heavy rain.
However, if at some point on its way up the wind gets diverted horizontally, it begins to spiral. Once it gets spinning fast enough, we get that baby hurricane, or tropical depression.As water from the ocean condenses in the air it releases energy as heat. This is the very energy that will intensify and drive that baby storm into a tropical storm or full-on hurricane. The condensation is also what produces all the rain that comes with a hurricane, and the heat released helps the storm itself rise in the air. As it rises, it sucks up surface air, which creates a low-pressure area in the center, also known as the ‘eye’ of the hurricane. This is why if you’re under the eye of the storm, the weather is eerily calm compared to the strong winds and heavy rain you would experience under other areas of the storm.
A hurricane is like a giant, self-sustaining heat engine – it keeps itself going unless the process is stopped. Condensation of the ocean water releases heat, which draws moist air from the ocean up into the eye of the storm. The moist air cools, which means there is more condensation, which leads to more heat being generated. This brings additional moist air up from the ocean, which cools and condenses. And you can see how this could continue on indefinitely!But we know that hurricanes don’t continue on forever; they are eventually stopped. This happens one of two ways: either strong winds disrupt the flow of the storm while it’s over the ocean or the storm moves over land.Once it moves over land, the hurricane runs out of fuel because it runs out of water to perpetuate the cycle.
The ocean is like a food source for a hurricane – it provides it with energy to grow big and strong. Once over land, though, the food source runs out and the storm is deprived of the energy it needs to keep going, essentially starving to death.Think about Oklahoma again. No hurricanes, right? This is because Oklahoma is too far inland. A hurricane needs a continuous supply of energy to soldier on, so once it hits land and quickly runs out of fuel, it has no hopes of making it much farther inland than the states that border the Gulf of Mexico and Atlantic Ocean.
Hurricanes are like living storms. They start out as small baby storms, develop into adolescent ones and may eventually become full-sized, adult storms if they get enough energy to build up that large.
Hurricanes develop from tropical winds over the ocean. Most of these winds move vertically and create thunderstorms. Sometimes, though, the winds get diverted horizontally and start spinning.
If the spinning winds pick up enough energy, they may become tropical depressions, which have winds less than 39 mph, or even tropical storms, which have winds between 40 and 73 mph. If the winds of the storm are more than 74 mph, this is a full-fledged hurricane. Once it becomes a hurricane, it is further classified by its wind speeds.
A category 1 hurricane is the least dangerous, with wind speeds of 74 to 95 mph. As it grows, it may become a category 2, 3, 4 or 5 hurricane. If it reaches category 5, this is an extremely dangerous storm with wind speeds of 155 mph or more!All of these storms get their energy from ocean water, which acts as a food source for the storm. Water condensation from the air releases heat, which provides energy. The condensation also creates all the rain that generally comes with a hurricane.
The heat that’s produced from the condensation warms the air, which causes it to rise. As it rises, it sucks up surface-level air and creates the low-pressure eye of the storm. This cycle continues until the storm is disrupted by stronger external winds, or, as is more often the case, it hits land. Just like you would starve to death without food, the hurricane starves without water.
There is no longer an energy source for it to continue its cycle, and it eventually dies out.Because hurricanes need water, you will not experience this type of storm if you don’t live along the coast. Louisiana, Florida, South Carolina and other Southeastern states experience hurricanes because they provide a buffer wall that hurricanes hit, causing them to die out before they can go farther inland. States like Oklahoma, Colorado and Tennessee are too far inland to experience the wrath of hurricanes because they’re too far from the ocean, the ultimate source of energy for these dangerous storms.
When this lesson is finished, you should be able to:
- Describe how hurricanes are formed
- Detail the types of tropical storms
- Explain why hurricanes are water based