thanks Trevor.
It certainly is interesting to speculate on how a spot might survive in the extreme winds of the equatorial zone. This spot has not changed much in appearance in nearly 3 weeks (maybe slight elongation in the last image), so it is presumably being carried along as a coherent structure embedded in the moving "surface" - and moving at close to the system 1 wind speed. This is not without precedent though - a BAA report on a 1994 equatorial spot noted " The spot therefore seems to be a long-lived phenomenon with no significant change over the past tens of rotations."
http://www.physics.sfasu.edu/astro/saturn/spots.html
Other equatorial spots have rapidly elongated, so I guess there must be more than one formation mechanism.
regards Ray