Is it true that low pressure weather systems spin clockwise south of the equator? If so, could a storm like a hurricane cross the equator? What happens to a low- or high-pressure system that does cross the equator?
It’s true and that’s a good question which the meteorologists on board may be able to answer. However, IMHO, hurricanes only occur in the northern hemisphere. I have never heard of one S of the equator. If they originate in the Atlantic or in the Pacific E of the Date Line, they are called “hurricanes.” If they originate in the Pacific W of the Date Line, they are called “typhoons,” except for an area in which they are called “cyclones.” I don’t recall where that area is.
I further think that these systems, high pressure areas and low pressure areas, never cross the equator due to their spin and the earth’s spin.
So, if storm systems cannot cross the equator, does that mean that the northern and southern hemishperes are isolated from each other as far as climate and weather go? Are storms caused by low pressure systems uncommon at the equator?
I’m not a meteorologist. I said that was my opinion. There are areas near the equator called the doldrums, and well illustrated in the Rhyme of the Ancient Mariner. I believe that near the equator, the rotation of the Earth is such that cyclonic and anti-cyclonic systems do not form. That is my guess, but I may be wrong. There are plenty of rains near the equator, but those are caused by the radiant heat in the areas.
From the Brittanica Ency. “the doldrums”:
equatorial regions of light ocean currents and winds within the intertropical convergence zone, a belt of converging winds and rising air encircling the Earth near the Equator. The northeast and southeast trade winds meet there; this meeting causes slow air uplift and produces the doldrums. They occur along the Equator in the Indian and western Pacific oceans and slightly north of the Equator off the African and Central American west coasts. The crews of sailing ships dreaded the doldrums because their ships were often becalmed there; the designation for the resultant state of depression was apparently thus extended to these geographic regions themselves.
This would indicate that storms do not occur in the belt of converging winds.
There is a lengthy discussion of this topic in a recent book called Isaac’s Storm. It’s not a scholarly scientific work, but it includes what seems to be a fairly detailed layman’s account of what the author, Erik Larson, calls “The Law of Storms.”
I tried to find a quote which would directly answer your question, but couldn’t right offhand. However, I believe the book tends to confirm what barbitu8 has said.
Finally! A thread I feel remotely qualified to answer! Woo hoo!
Yup, a hurricane, like all low pressure systems, spins counter clockwise (cyclonically) in the northern hemisphere and clockwise (anticyclonically) in the southern hemisphere. As for crossing the equator - no, they don’t cross the equator. In fact, no hurricane has been within 5 degrees of the equator. Essentially, a hurricane develops as warm water of the west coast of Africa (i’m using north Atlantic storms in this example) leads to a large area of thunderstorms. (Really simplified: Water + heat + unstable (rising) air = thunderstorm) These storms feed off one another as they travel eastward across the Atlantic. The Coriolis effect acts upon this mass of storms, and the whole system starts to spin. As the system moves farther from the equator, the spin gets tighter, as it gets closer to the equator it gets looser. Once it got to the equator, it would just be a mass of thunderstorms.
As for the hemispheres being isolated weather wise, I have loads of note about Hadley cells and such things somewhere. I’ll dig those out and give you a proper reply.
I have several books which say this so much better than what I just said (I’m getting a geography degree and hope to make weather and climate my area of expertise)But sadly, the books are all currently packed while I move so I can’t give you a half decent cite or anything.
You might what to check out NOAA’s website for info (I think that it’s http://www.noaa.org)
Sorry to reopen such a long thread, but I recently found the answer. The magnitude of the Coriolis force is a function of velocity and distance from the equator (latitude). Hence the stronger the velocity the greater the CF. And likewise, the farther from the equator, the greater the CF. It has a value of zero at the equator. Hurricanes must have CF in order to continue rotating. This is why you will never see a hurricane cross the equator, because it would dissipate like nothing you’ve ever seen before. This is basically what Miss Gretchen posted, but I find the above more explicit.