Cloud direction and weather systems differ from Morrowind
During "normal weather" the clouds are always going north no matter where the player is standing in Morrowind, but during ash and blight storms the animation rotates constantly depending on witch side of red mountain the player is standing on. So Ash and Blight storms "follow" the players position in a sense. So does the wind forces affecting the player and the dust particles (neither witch is present in OpenMW at this time).
One does not notice the animation rotating during normal conditions, but increasing the player speed to 2000 and moving sideways you can clearly see that ash and blight storms rotate so that it always comes from Red Moutain whether you stand north, south, east or west of it.
(RM-245 from redmine: created on 2012-04-01 by William Sogge, , closed on 2014-06-29 by scrawl ., relates #41 (closed))