Squall Line

Decorative Image: Squall line thunderstorm diagram. Straight line winds, found with many squall lines, are more common than tornadoes here.

• Several storms organize to form a line

• Lines of storms can be over 100 miles long and move at 60 MPH

• Straight line, potentially damaging, winds are the main threat

• Hail, weak tornadoes (gustnadoes) and flooding also possible

Decorative Image: Image of a shelf cloud from eastern Kentucky.

Speaker Notes:

• The next step up, in terms of severity, of thunderstorm types is the squall line.

• Squall lines are much like multi-cell clusters, in that, severe cells are organized in a line, except each of these cells are in the mature stage.

• These squall lines can extend hundreds of miles in length.

• The biggest severe weather concern with squall lines are damaging non-tornadic winds called “straight-line” winds. Straight line winds are more common than tornadoes in this part of the county, and their speeds can easily exceed 60 MPH and produce tornado like damage. This is why when the NWS issues a severe thunderstorm warning, one should take the same precautions as a tornado warning, because the destruction can be the same.

• In addition to wind, large hail is possible, as well as flash flooding if the squall line ‘trains’ across the same area. Weak tornadoes that form on the leading edge of the rain cooled air, called gustnadoes are also possible.