There are rare counterexamples on Earth of anticyclonic tornados. Check out YouTube for some cool videos. However, the GRB is a conventional storm of the low pressure variety; it's hard to think of what a real high pressure storm would be like. The mainstream claim is that the GRB is different from Earth bound hurricanes: the former is supposed to be driven by high pressure, whereas the latter is driven by low pressure. To escape this result by definitional fiat, well, we might as well call Earth-bound hurricanes high pressure storms. Still haven't found that paper that agrees with my model yet though. . . .