Which of the following is NOT a type of Mesoscale Convective System?

The choice of Squall Line as not being a type of Mesoscale Convective System is based on the definition of mesoscale convective systems and how various types fit into that classification.

Mesoscale Convective Systems (MCS) refer to organized groups of thunderstorms that can span from a few kilometers to several hundred kilometers in size and often have significant weather impacts. Types of MCS include the Mesoscale Convective Complex, which is an organized system of thunderstorms that maintains its structure for several hours, and the Mesoscale Convective Vortex, which is characterized by a rotating convective system that can lead to strong winds and precipitation.

Derechos, also categorized within this framework, are associated with widespread and long-lived wind events that arise from intense thunderstorm clusters typically associated with a squall line. However, a squall line is not classified as a distinct MCS because it specifically refers to a linear arrangement of thunderstorms, which can actually be part of an MCS but does not fulfill the definition of one on its own since it lacks the broader, organized structure commonly associated with an MCS.

Understanding the nature of these systems aids in recognizing how they function within meteorological contexts and helps distinguish between the various manifestations of