Summary

This is a report on the phenomena recorded in amateur images of Jupiter in the first half of the 2010 apparition. The South Temperate Region now contains just two segments of dark STB, since a third formation, the STB Remnant, collided with the segment f. Oval BA and radically changed the region around it. Dark spots streaming Sf. from this STB segment are merging into a single dark ring in the STZ, which has become methane-bright during the mergers. Oval BA has just passed the Great Red Spot (GRS). Both STB segments are emitting exceptionally dense streams of spots in the STBn jetstream. The South Tropical region is the most radically changed, as the SEB has faded almost completely, leaving bands of unusual pale pastel colours. The GRS is a great red oval, with a blue triangle and sometimes a mini-plume to its north. The SEBs is scallopped by a continuous chain of small faint spots (see Appendix). The SEB still contains five barges but they have undergone a reversal of contrast as the belt faded. On the SEBn, the S. Equatorial Disturbance has disappeared, and fast-moving disturbed sectors have reappeared on the jetstream.

An Appendix analyses in detail the motion of the chain of spots on SEBs. Their retrograding speed is much less than the normal speed of the jet slightly further north, but gaps in the chain move with full jet speed. We conclude that the speed profile of the retrograde jet is unchanged, but the chain of slower-moving spots is a meteorological aspect of the SEB Fade. The northern hemisphere will be covered in the second half of this report.

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