Energy and momentum.
There was a very short news article or sidebar a few years back in
Scientific American in which models of Jupiter with rapidly and
differentially rotating bands of atmosphere were able to keep GRS-type
storms persistent for long periods of time. It will probably
dissipate eventually. It has persisted for at least 170 years.
I think it's very interesting that the concentration of the reddish
pigment varies periodically and inversely with the concentration of
the reddish pigment in the South Equatorial Belt.
Internal heat and rapid rotation drive the weather on Jupiter, which
is quite unlike the weather on Earth.