Using data accumulated over the past four years by Venus Express, scientists have shown that the giant double vortex storm at Venus’s south pole was only a temporary phenomenon. You can download the actual paper here [pdf]. Key quote from the paper:
The polar region of Venus shows a dynamics regime quite different than the rest of the planet, with a separation region delimited by the cold collar zone. Average wind speeds presents an almost solid body rotation, while instantaneous view highlights the complex dynamic structure with air flowing almost toward all directions. The so called dipole shape is not a stable feature and the morphology of the vortex is significantly variable on both short and long timescales.
The “cold collar” is an atmospheric ring of colder temperatures that encircles the planet’s poles.