Squall line

A squall line, or more accurately a quasi-linear convective system, is a line of thunderstorms, sometimes involving severe weather hazards like isolated tornadoes and sudden, heavy downpours.They can form along the boundary of a cold front or ahead of one, and can produce strong gusts up to 40–60 mph. Squall lines can be an indication of severe weather, capable of lasting 30 minutes in appropriate conditions. A squall line is typically hundreds of miles long but only 10–20 miles wide. A squall line is classified as a derecho if it produces damage over hundreds of miles, with winds capable of reaching 100–120 miles per hour.

Primary hazards include:

• Brief, isolated tornadoes

• Mesocyclones

• Downbursts/microbursts

• Frequent lightning

• Strong gusts up to or over 40 mph
• Heavy precipitation of 1–2 inches per hour, sometimes 3—4 inches per hour in historic conditions

References