I looked this up and it said the Coriolis effect so I looked that up and I have no clue what it’s talking about…
In: 222
If you ever flush a toilet bowl in the opposite hemisphere (north/south) of where you grew up, you’d witness the same effect.
There’s the Newton thing about objects moving in a straight line unless another force interferes. That’s in play here.
The earth is about 24,000 miles around, so it moves at 1000 miles per hour at the equator. A object moving due north from the equator would have a starting eastward motion equal to the equator speed. Ignore air friction for the moment, please.
Now let’s say that object, a parcel of air (some arbitrary volume) moves north to 45 degrees north. The size of the earth gets smaller as you move toward the poles, so the ground speed is only 700 miles per hour now. Keep going to the North Pole and it’s zero! The parcel, because it moves north from the equator is moving east faster than the ground under it is moving east. The effect of this is the track of the parcel turns toward the right.
Now let the parcel move south from 45 North — it’s now slower than the ground speed at lower latitudes, so it turns right again as it travels!
This direction change is called the Coriolis Effect. In the Northern Hemisphere, the effect causes a moving parcel to turn right in the long run. In the Southern Hemisphere, it’s a left turn.
Oh! you say — what about east and west? A straight line on a sphere is called a Great Circle path. At the equator, it’s a straight line parallel to the equator. At the poles, it’s any of the longitude lines going north and south. But, if you’re at, say 45 north, your great circle will eventually cross the equator 90 degrees east or west of your position. And, oops! you’re moving toward the equator (south) again, so it turns to the right. Left, in the Southern Hemisphere.
Now, hurricanes: High pressure systems are regions of descending air parcels heaped up over an area. The heap is what causes the higher pressure. But, air is fluid, so it drains from that area, and in moving away, Coriolis makes it turn right (Northern Hemi), so the High overall has clockwise flow. And opposite in the Southern Hemi, of course.
A Low pressure system contains rising air. The rising air is replaced by air moving toward it from the outside, again because it’s a fluid, and the atmosphere likes balance. But — Coriolis is too weak compared to the forces moving air toward the center of the Low, so it spins around the Low as it moves toward the center. Thus, counter clockwise flow. (Opposite in SH)
A hurricane is a special type of really, really wound up Low pressure system, so the air flowing into and around it can get up to hundreds of MPH/ KPH toward the center.
Oh – where does the air go? Out the top! Eventually the rising air runs into a temperature change from the lower atmosphere (Troposphere) to the next layer (Stratosphere) and moves out and away from the center. The temperature changes stops it from getting any higher, mostly.
Same with thunderstorms. Moist air in the bottom, then up to the feathery tops at and under the Stratosphere. And a hurricane/typhoon/cyclone is a type of organization of thunderstorms.
Take a clear piece of plastic, a window, or something transparent that you can draw on with a dry erase marker or sharpie. Draw an arrow going clockwise on one side. Now flip it over and look at it from the other side.
Alternatively, If you have a friend, face them and extend your arm forward. Use your arm to make some small circles in the air going clockwise, ask your friend what direction they observed your arm moving.
You see looking at a rotating object from two different perspectives will give you differing results. If you move your arm clockwise your friend will observe your arm going counterclockwise
Now imagine you are in space looking straight down from the north pole watching the earth rotate. You watch a plane depart from the north pole in a straight line towards the equator. the earth rotates under the plane. (Edit: Planes start off rotating with the earth, but a plane rotating with the earth at the pole rotates in a tiny circle while a plane near the equator rotates in a large circle. As the plane near the pole takes off and flies towards the equator the plane is still trying to rotate with the tiny circle from the pole but the ground moves faster under the plane at the equator) Now imagine the same thing from the south pole view. You see the same effect but in the opposite direction. That’s the coriolis effect.
[This graphic](https://cdn.britannica.com/11/113711-050-1ECECE85/path-rocket-effect-North-Pole-Coriolis.jpg) shows what I’m trying to explain.
As for why hurricanes rotate in the opposite directions imagine some air moving away from the north pole but towards the center of the hurricane. Because the coriolis effect the moving air is deflected slightly to side of the hurricane. This effect continues as it goes round and round in the hurricane. [Like in this image](https://scijinks.gov/coriolis/hurricane-direction.png). To imagine the southern hemisphere you just have to image the same thing but from underneath just like directions mirrored when you looked at the other side of the plastic sheet from earlier.
Imagine you’re in a big bathtub full of water, and you have a special toy boat that you want to make move in a circle.
Now, if you were to stir the water with your hand to make the boat go around, you might notice something cool: the water near the drain starts moving faster and makes the boat spin around too. But if you’re in the Southern part of the tub, the water near the drain moves the other way, and the boat goes around in the opposite direction.
Hurricanes are like giant swirling storms in the sky, and they’re made of air. Just like the water in the bathtub, something called the Earth’s spin affects how they move. In the Northern part of the Earth, the air around a hurricane starts spinning counterclockwise because of how our planet turns. But in the Southern part, it spins the other way, clockwise, because of the same spinning Earth.
So, when you look down on a hurricane from above, in the Northern part, it looks like it’s going around to the left, and in the Southern part, it looks like it’s going around to the right. Just like your toy boat in the bathtub!
Imagine your sat on an office chair and you spin round really fast.
If you stuck your legs out you slow down and if you tuck in you speed up. This is because your legs conserve momentum and as they go further out they need more engery to turn at the same speed.
As the air in a hurricane moves north it still has a lot of momentum fron the earth spinning and unlike your legs isnt connected to anything so it can speed up itself.
ELI5: Everything should just “fly in a straight line” along the surface of our globe right? No, because the planet rotates. You shoot a cannonball ( while in the Northern Hemisphere) in a straight line north-east, and it will go slightly towards the equator because the Earth spins while the cannonball is still in flight.
Hurricanes are formed by winds (particles of gas and dust), which are subject to many different forces, but also the Coriolis, i.e the Earth’s rotation-caused “nudge”. The only thing that may be truly confusing is that this is not a “real” force; there is no push on these objects (because it’s just the inertia/frame of reference that seems to “push” the objects) and you can show this by math, that it’s just a frame of reference thing: you include the planet’s rotation and let the cannonball fly while the Earth spins and you watch from a still point from space, it becomes more obvious why it should curve from a straight path.
So what happens if it crosses the equator?
The earth is spinning. The equator is the outside of the spin. If you have a thick viscous substance and run a toothpick through it, making the line of the equator, the liquid above the line will spin counter clockwise and clockwise below the line.
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