Squall Line

• A horizontal cloud feature detached from the storms and rolling in the direction of the wind along a horizontal axis

• Roll clouds are not as common as shelf clouds

Roll Cloud

Both the shelf/roll cloud indicate the edge of the updraft/downdraft interface

Decorative Image: Roll Cloud. Just like the shelf cloud, the roll cloud indciates the onset of wind. Decorative Image: Another image of a roll cloud.

Speaker Notes:

• Sometimes there is a cloud ahead of an approaching squall line that rotates horizontally, like a rolling pin. This is NOT a tornado, but is a roll cloud.

• The roll cloud is detached from the squall line and indicated the edge of the updraft/downdraft interface. Just like the shelf cloud, the roll cloud indicates the onset of wind.