"Washboard" Cloud Structure (WCS)
The "Washboard" Cloud Structure could be distinguished because it has been observed in its shape over and over again.
It is observed not often but regularly over an open ocean. The more than 50% of all observation cases lies over the Indian Ocean, in the south of equator from June to September (usually July - August - summer monsoon season), but also over the central Pacific (April - July), eastern Pacific (November, December) and, less commonly, via Atlantic. All observation cases are currently between +20 ° and -25 ° around the equator.
The structure has usually a "trunk" of the high convective clouds, from which deeper and thinner cloud streets branch vertically or at an angle off, and can produce himself the new twigs. Of course, then mixed the wind the whole picture.
The origin of this Structure is unclear. It can be assumed that the cold air masses that fall along the edges of the convective clouds down, form an unstable rolling eddies, which can be the cause of the emergence of the cloud streets structures.