Originally Posted by korjik

tornadoes are not big enough to really feel the coriolis effect so anticyclonic tornadoes are not truly suprising. They also have nothing to do with what we are discussing.

There is no 'definitional fiat' either. If you have an object moving with a velocity in a rotating system, its motions are defined by Newtons Laws. The velocity changes in very specific ways. When you add how pressure changes effect any free moving fluid, you get a very specific set of motions.

For a normally rotating object, that is an object rotating in the same direction as Earth, with a pressure disturbance in its southern hemisphere, you have one of two cases. If it is a high pressure system, the air tries to flow outward from the center but is deflected via the coriolis effect into a counter-clockwise rotation. If it is a low pressure system, the air tries to flow inward and is deflected into a clockwise direction.

So, if you know the direction of rotation, you know the sign of the pressure differental. When you check terrestrial sources, you see that known pressure differentials follow this law. You will see that typhoons (is that correct terminology anyone?) in the south pacific, which are known, measured low pressure systems rotate clockwise and high pressure systems rotate counter-clockwise.

When you look at the Great Red Spot, you see that it is rotating like a terrestrial high pressure system. Since we only used Newtons laws to derive the motion of the winds, either the GRS is a high pressure system, or Newtons laws dont work on Jupiter. There isnt any way around this.