Types of severe storms

In addition to supercells, the atmosphere generates a number of different types of severe storms. A large class of these storms are called Mesoscale Convective Systems. They appear in many forms and include:

  • Squall lines
  • Bow Echoes
  • Derechoes
  • Mesoscale Convective Complexes

Squall Lines

  • A squall line may be thought of as any line of convective cells.
  • It may be a few tens of kilometers long or 1000 km long (>500 nm)
  • there is no strict size definition.
  • Squall lines are usually composed of a series of ordinary cells spread along and behind the leading edge of the system.
  • However, a squall line may also be composed of a series of supercells.
  • Behind the leading edge of the squall line is often an extensive region of stratiform precipitation.


Explain why squall-line thunderstorms often form ahead of advancing cold fronts but seldom behind them.