Question about Hurricane Alex

The Coriolis force actually gets stronger as you move away from the equator. Tropical systems could technically form at 80°N if the sea-surface temperatures and other conditions were favorable (which they never are).

The Coriolis force is too weak near the equator to allow a storm to form. It varies with latitude according to the equation f = 2 * omega * sin(latitude), where f is the Coriolis force, omega is a rotational constant of the Earth (equal to 7.292x10^-5 radians^-1, if I recall correctly), and the latitude is something like 45 degrees. The sin of 0 degrees is 0, making the Coriolis force non-existant at the equator. At 5°N, f is only equal to about 1.27x10^-5 -- whereas at 45°N, it is a full ten times larger.

In layman's terms, the Coriolis force is too small to support a circulation at low latitudes due to the force balance between it and the pressure gradient force (the magnitude of which is determined by the difference in pressure between two points; also note that there are other forces besides these two in consideration, but these are the predominant ones). It also helps to explain why storms become deflected to the right of their motion - i.e. recurve - with time & increasing latitude.

(Footnote: I was about to tackle this one, but I'm sure glad that you did

. It is also a primary factor in the circulation of storms, i.e., counterclockwise in the northern hemisphere and clockwise in the southern hemisphere. In a classic model, your answer is correct, but in the real world the actual 'zero' force point resides at about 5N in the northern hemisphere winter and at about 10N in the northern hemisphere summer - because of the tilt of the earth's axis. Which explains why some of these low latitude Cape Verde systems take such a long time to spin up. A system that emerges off the African coast at 9N has a much tougher time of it than one that emerges at 12N if other factors are otherwise equal. Thanks for the superb answer.)
ED

Edited by Ed Dunham (Wed Aug 25 2004 12:10 AM)

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