As I know, due to Coriolis force, hurricane in each hemisphere can spin in one direction only. But I also know hurricane can be formed near equator, which colriolis force is weak. My question is, is it possible that a vortex spinned in opposite direction is developed into hurricane near equator?

  • $\begingroup$ Very related questions, though not sure they're entirely the same. One is can an existing vortex cross over (which as far as I understand it, does happen, though typically not organized/intense enough to maintain TC designation). The other is whether one could form, which would be a very daunting idea, as there'd really be no force to develop any kind of tangential wind. Small-scale vortices (antimesocyclones) do form, but as I understand it, they're only due basically to vorticity segregation due to pressure perturbations. Don't think formation of an anticyclonic TC is feasible at all. $\endgroup$ – JeopardyTempest Jun 9 '17 at 9:36

No, a small vortex in a contrary rotation might develop into something larger if conditions were right, and there was no horizontal shear, but it wouldn't last long. The Coriolis force would work against it, and it would fizzle out.

Also, hurricanes don't form near the equator - there isn't enough horizontal rotation to kick-start it. Hurricanes initiate a little to the north or south of the equator.

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  • $\begingroup$ Gstestso: Without any additional forces, winds would just flow into any low-pressure developing, and quickly fill it in (more air = more pressure). That "Coriolis force"... i.e. the rotation of the Earth... is what shifts wind from in-ward flowing to a low, to turning more tangentially, until it becomes more circular. The resulting concoction is called gradient wind balance. $\endgroup$ – JeopardyTempest Jun 9 '17 at 9:45
  • $\begingroup$ Localized vorticity generation can cause bits of anticyclonic rotation to develop. But over the long run, any anticyclonic rotation will be fighting against Coriolis continually. Picture it like trying to run fast against the flow of a large marathon of people (early on, when they're all bunched up). You might be able to get moving a bit for a few moments with some luck (indeed, small anticyclonic swirls may occasionally be seen in pockets of developing TCs?), but soon the incessant swell of people would disrupt your success. And if a storm will "succeed", it'll thus need cyclonic rotation. $\endgroup$ – JeopardyTempest Jun 9 '17 at 9:48
  • $\begingroup$ A hurricane or other cyclone with winds inspiraling clockwise in the Northern Hemisphere or counterclockwise in the Southern Hemisphere is not anticyclonic --- it is still a cyclone --- but antibaric. Except on the smallest scales such as dust devils or whirlpools, antibaric cyclones are very difficult to initiate, but once initiated they can be stable. Hurricanes have existed with the eye as close as approximately 1 degree of latitude from the equator. The part of the circulation on the other side of the equator is antibaric and operates just fine. $\endgroup$ – Jack Denur Sep 25 '17 at 6:27

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