Why do hurricanes rotate? As you watched the recent activity of hurricanes, no doubt you sat there wondering why hurricanes rotate counterclockwise. It has to do with something called the Coriolis Force resulting from the spin of the Earth going counterclockwise as viewed from above (astronomers say viewed from the north) in the Northern Hemisphere (and will rotate clockwise in the southern Hemisphere). the reason for this is that the Earth rotates faster at the equator than near the pole.*
Imagine if a person were to stand at the North Pole and throw a ball far enough to reach the equator — say, to a person standing in Quito, Ecuador — the ball would not actually reach that person because it would not travel in a straight line. Since the equatorial region is moving faster than the North Pole, the ball would end up to the west of its target — somewhere in the Pacific Ocean, probably.*
The same thing would happen in the Northern Hemisphere if someone were to throw a ball from south to north, only the ball would end up east of its intended target.*
This is what happens to the winds that travel to and from the poles. In the Northern Hemisphere, winds moving north are diverted eastward, and winds moving south are diverted westward. In the Southern Hemisphere, winds traveling toward the equator will move eastward, and winds traveling toward the South Pole will curve west.*
..................................................................If there were no Coriolis effect, air would simply rush into the low pressure center, "since nature abhors a vacuum, and a low pressure area is a partial vacuum," said Chris Landsea, a Science and Operations Officer at the National Hurricane Center.*
It follows that you cannot have hurricanes at the equator because everything moves at the same speed, but there have been hurricanes observed 7 or 8 degrees from the equator.* So if you want to be safe from a hurricane, live on the equator.
Why did Hurricane Irma turn north?** There was a strong high pressure area to the East of the tornado blocking movement to the east and another to the west Though not as strong but still blocking the hurricane from moving west. It found a way to move to the north between the two high pressure areas so that is where it went. Because of the rotation of hurricanes, they want to move northward naturally at any rate.
Jet Stream Not surprisingly, the jet stream flows counterclockwise across the U.S. in the Northern Hemisphere in a undulating pattern (see figure) because of the Coriolis Force.***
Tornadoes Most tornadoes spin cyclonically (about 98%), ie, counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere but the Coriolis Force is not strong enough to make this a certainty.****
* https://www.cnbc.com/2016/10/07/heres-why-hurricanes-spin-counterclockwise-in-the-north.html
**http://miami.cbslocal.com/2017/09/08/why-hurricanes-turn-north/\
http://www.katc.com/story/36302637/why-irma-will-turn-north-and-not-go-into-the-gulf
*** http://www.businessinsider.com/jet-streams-coriolis-effect-earth-faster-fly-west-2016-2
**** https://www.loc.gov/rr/scitech/mysteries/coriolis.html
https://en.wikipedia.org/wiki/Anticyclonic_tornado
