Tropical Cyclones! Science Behind the Everyday, Part 3
Hurricanes, typhoons, and cyclones - these all refer to wild, reckless, and extremely destructive tropical storms that form all around the world. While only a handful of these storms develop into full scale hurricanes (around 6 hurricanes a year happen in the Atlantic Ocean), a bunch more become tropical cyclones. These raging torrents have winds anywhere from 30 to 215 miles per hour and form around 100 times per year! In this third part of the Science Behind the Everyday Series, we’ll be learning some basic things about tropical cyclones - what they are, how they form, and some really intriguing (but frightening!) facts about them.
Naming
It’s important to know that hurricanes, typhoons, and cyclones are just different names for tropical cyclones. The reason there are these different names is because different areas around the world call topical cyclones by different things. Here’s a map of that:
What are tropical cyclones?
Tropical cyclones are violent, spinning storms that form near the equator. Because of easterly trade winds that blow from the east to the west, cyclones are usually pushed to the west, hitting places like Florida. Here are some basic ingredients for a cyclone:
The ocean has to be at least 79-82 degrees F
There has to be enough humidity, or moisture in the air (at least 50% relative humidity)
Enough wind, but not too much - too much wind will rip apart the cyclone before it even forms!
Because of these conditions, tropical cyclones form mostly around the equator, where there’s the most sunlight and the waters are the warmest. Cyclones can’t usually form in places that are 30 degrees above or below the equator - the water is simply too cold here.
How do tropical cyclones form?
When these three conditions (and a few others) are met, a tropical cyclone can form. It all begins with the sun. When the sun warms up the ocean, some of the water at the surface evaporates and rises as water vapor. Taking its place are high pressure winds that come from places farther from the equator. It’s a basic law of science that air travels from high to low pressure. Because the rising water vapor creates an area of low pressure, higher pressure winds rush in to fill its place.
But, something strange happens. As these high pressure winds rush into fill the space left by the rising low pressure winds, they are curved and begin to wrap around this space, hardly actually reaching it! This is called the Coriolis Effect and it happens because the Earth is round and spins. Because of this, cyclones above the equator in the Northern Hemisphere spin counterclockwise and clockwise in the Southern Hemisphere.
The low pressure space that the winds don’t actually reach and just spin around is called the eye of the cyclone. This is why the eye of a cyclone is so peaceful and calm. These eyes are anywhere from 19 - 40 miles wide, while the whole cyclone is anywhere from 60 to 1240 miles wide!
As all of this is happening, clouds are towering high up into the sky and spinning around the eye. But why? Well, as humid air rises, it eventually condenses into clouds. Tropical cyclones have a lot of tall, towering clouds that rise high into the atmosphere. And as you know, clouds can release rain, and this is exactly what happens in a tropical cyclone. Lots of high speed winds and heavy rain fall!
After this rising air cools, it then sinks down around the cyclone because it is high pressure and wants to go back to the low pressure area. This cycle of air flowing up, down, and around generates a ton of energy, allowing cyclones to reach speeds up to 215 miles per hour! In fact, a tropical cyclone generate around 40 times more energy than all of mankind does in one year!
That’s it for this short introduction on tropical cyclones. But stay tuned - in the next part we’ll explore the most extreme cyclones that have ever occurred on Earth!
