The ASI is in kph. He's doing about 100 knots at 4300rpm with the VSI showing a slight descent (I think the VSI is in m/s, which would mean a descent rate of just over 2 knots.)
Flying that fast with the engine at idle would indicate that the cloud was sucking the aircraft up & he was diving to escape. 100 knots at 4300rpm seems a fairly standard cruise setting for a Rotax 2-seater so its unlikely that the cloud was particularly active & at that speed they will be out the other side in less than 2 seconds.
Is the turn co-ordinator even switched on?