EDIT: If you're new to this thread, you can save yourself a lot of reading by skipping directly to post #78, where the fully developed theory is presented.

The idea that Jupiter's Great Red Spot is a high pressure system is a mainstream idea, as evidenced by a quick google search of "Great Red Spot is a high pressure system". Of the four results returned, there are three prominent mainstream sites: space.com, nasa.gov, and our own bautforum.com that perpetuate the claim. This urban astronomical myth has been perpetuated most recently here by Robert Tulip in the What will become of Jupiters spot? thread.

Indeed, the myth that Jupiter is a high pressure system has been promoted by that great mythbuster, The Bad Astronomer himself on his very own blog!

As Phil notes, the primary evidence that the GRB is a high pressure system is that it is located in Jupiter's southern hemisphere, yet it is rotating counterclockwise--the direction opposite observed by all hurricanes (a.k.a. "cyclones" as they are known Down Under) in Earth's southern hemisphere. This interpretation of the evidence is spurious, however.

The primary evidence that the Great Red Spot is a low pressure system involves the ordinary behavior of such systems. In an atmospheric high pressure system, cold high pressure flows outwardly from the center of the system along the lower boundary layer. Ideally, such air will then rise and return to the center via a central downwelling zone. However, since cold air is denser than warm air, it tends not to rise. That's why high pressure zones on Earth aren't very windy--they just don't do very much. In low pressure zones, on the other hand, warm surface air is sucked to the central zone and then rises around the "eye" to the upper boundary layer where it cools and spreads. It strains crudulity think that Jupiter would be doing the opposite.

Therefore, the Great Red Spot is indeed an ordinary Earth-like storm. What we really observe on Jupiter is the upper layer of an ordinary low pressure storm. In an Earth-bound hurricane, the upper layer of the air mass consisting the hurricane does indeed move in an anticyclonic direction--we just don't observe that rotation in satellite photos because the upper layer is transparent, whereas the lower layer is loaded with clouds. As the warm, moisture-laden air rises, it releases its moisture in the form of rain, becoming transparent.

Thus, my model predicts that the air comprising the GRB is opaque. Presumably, its lower layer that we can't see rotates in the ordinary cyclonic fashion.

This is going to be fun. . . .

As a side note, I reached my conclusion by applying the teleological methodology of reverse engineering that I promoted in my previous ATM thread. The Great Red Spot is the most well designed, perfect storm in the solar system. Yet high pressure designs are the worst possible designs for storms. It was therefore inconceivable to me that the high pressure system model could be correct. This allowed me to quickly zero in on the true explanation.
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