APOD: 2021 September 15 - Cyclone Paths on Planet Earth

Good morning, Rallypoint. Today's Astronomy Picture of the Day (APOD) is titled "Cyclone Paths on Planet Earth." Juxstaposed against a GOES satellite mosaic of the Earth, we see all hurriance/cyclone paths from 1985-2005. And we also see the Coriolis Effect in action on major storms. The effects are two-fold: 1) storms form away from the Equator and 2) storm movement arcs away from the Equator.

But why? The Coriiolis Effect is caused by the rotation of the Earth. Imagine if you were standing one foot away from the North (or South Pole). In 24 hours you would travel a sum total of about 6 feet as the Earth completed one rotation. That's travelling at about 0.00005 miles per hour. Contrast that with standing at the Equator. You would travel some 25,000 miles in that same 24 hour period. That is about 1,040 miles per hour. Big difference, eh? And the further away from the Equator, the slower you would move.

Now stretch that out on a global scale and think about a hurricane. The drag of the Earth beneath it causes it to rotate as well (i.e. spin). What's the Coriolis Effect at the Equator? Zero. Storms largely form over water, and need to spin to feed themselves. Simple physics cause storms to move away from the Equator in an effort to keep spinning.

So why are there no storm tracks in the South East Pacific? My guess is that an area with the potential to spawn a low pressure center (a land mass or region of elevated water temperature) is too far away. And a check of global sea temperatures would show that such a guess would not be too far off.