[nudephil (OP)]

Dan asks:

Do all hurricanes that form in the Atlantic spin anti-clockwise, and is this spin influenced by the hurricane being above or below the equator?

Can anyone answer?

[Bored chemist]

I'm fairly sure that , if there are any hurricanes in the South Atlantic (They are rare) , they would spin the other way.
https://en.wikipedia.org/wiki/Hurricane_Catarina
And yes, the direction is due to the spin of the Earth

[evan_au]

They spin the same direction when viewed from space (eg from the distance of the Moon).
But I've never seen a weather map take the external viewpoint, either.

[Bored chemist]

Everything rotates clockwise- from some point of view.

[lucky33]

There is a theory that tornadoes spin in one direction in the eastern hemisphere. And in the western hemisphere the other way!

[evan_au]

the eastern hemisphere. And in the western hemisphere

I am interested in where you draw these Eastern & Western hemispheres.

At least the North and South hemispheres are well defined by the direction of Earth's rotation around its axis (which is what drives Coriolis force = drives tornadoes/hurricanes).

[Petrochemicals]

They spin the same direction when viewed from space (eg from the distance of the Moon).
But I've never seen a weather map take the external viewpoint, either.

Could you clarify that Evan please.

[Bored chemist]

I am interested in where you draw these Eastern & Western hemispheres.

From Greenwich, England.
Obviously.

[evan_au]

Quote from: evan_au on 09/09/2020 21:51:13
They spin the same direction when viewed from space (eg from the distance of the Moon).
But I've never seen a weather map take the external viewpoint, either.
Could you clarify that Evan please.

I understand that hurricanes don't often originate right on the equator, as the Coriolis force is near zero there.
- Hurricanes tend to form somewhat away from the equator, where the Coriolis force is greater.

When looking at a weather map, looking down on the low-pressure region in the center of a hurricane as if from Low-Earth Orbit...
- When originating in the Northern Hemisphere, hurricanes spin counterclockwise
- When originating in the Southern Hemisphere, hurricanes spin clockwise

Now take a step back, as far as the Moon (even geosynchronous orbit would be fine, provided it showed a whole-Earth view)
- You see a hurricane at mid-Northern latitudes, spinning counterclockwise
- You see a hurricane at mid-Southern latitudes, spinning clockwise
- Due to the curvature of the Earth, you will discover that as a point near the hurricane rotates around the central low-pressure region:
        - This point will be most distant from you when one in the Northern hemisphere is farthest North, and when the one in the Southern hemisphere is farthest South
        - After its most distant point, they will both then move to the left
        - This point will be closest to you when one in the Northern hemisphere is farthest South, and when the one in the Southern hemisphere is farthest North
        - After its most distant point, they will both then move to the right
        - So it is like looking at the spiral of a rolled-up newspaper, rotating in a single direction (parallel to Earth's axis of rotation).
        - The image of rotating in opposite directions comes from looking at opposite ends of the newspaper in a traditional weather map (LEO)
        - But when you take an external view, you can see that they rotate in the same direction.

Of course, you are highly unlikely to see a single image with a hurricane in both the Northern and Southern hemispheres, since hurricanes are driven by high sea surface temperatures, and these occur 6 months out of phase in Northern and Southern hemispheres
- But with continued ocean warming, who knows what is possible?

[Petrochemicals]

Quote from: evan_au on 09/09/2020 21:51:13
They spin the same direction when viewed from space (eg from the distance of the Moon).
But I've never seen a weather map take the external viewpoint, either.
Could you clarify that Evan please.

        - After its most distant point, they will both then move to the left
        - This point will be closest to you when one in the Northern hemisphere is farthest South, and when the one in the Southern hemisphere is farthest North
        - After its most distant point, they will both then move to the right
        - So it is like looking at the spiral of a rolled-up newspaper, rotating in a single direction (parallel to Earth's axis of rotation).
        - The image of rotating in opposite directions comes from looking at opposite ends of the newspaper in a traditional weather map (LEO)
        - But when you take an external view, you can see that they rotate in the same direction.

I think I understand, but the coiling of the newspapers would be in different directions still?

[evan_au]

the coiling of the newspapers would be in different directions still?

Take a flat newspaper.
- Now roll it up, so the entire newspaper is rolled in a single direction.
- If you look at the end of the newspaper, it is a spiral - like the spiral you often see around a hurricane, viewed from LEO.
- If you look at one end of the newspaper, it will spiral anticlockwise; the other end will spiral clockwise.
- This is how something that rotates in a single direction (because you rolled it in a single direction) can appear to have two ends that spiral in opposite directions.

It all depends on your point of view - locally, looking down on different ends, or viewing it holistically, from an external point of view.

[Halc]

I think I understand, but the coiling of the newspapers would be in different directions still?

Another way of putting Evan's analogy: The rolled up newspaper represents all storms anywhere on Earth. It is aligned north/south.  If Earth is transparent and you can see all the storms on all sides of the planet at once, then viewed from a considerable altitude above either pole, all the storms in both hemispheres would appear to rotate the same way.
You look at it from well over the south pole and every storm on Earth appears to rotate clockwise.  From over the north pole they all appear widdershins.

So for instance, Irene went directly over me. My small town was listed as one over which the eye traveled. Since I'm below it, I'm south of the storm, and it rotated clockwise from my point of view.
I've been in three damaging named storms, but Irene was the only one that really scared me.