Cloud is a roller down the level of air flow in a tube-like clouds, which usually signals the emergence of the arrival of the storm, very few cases appear in the storm time is coming to an end.

• 滚轴云是向下气流中一种水平管状云，它们的出现通常预示着暴风雨的到来，极少情况下也出现在暴风雨即将结束的时候。