Multicellular thunderstorm

Description

The formation of multicellular thunderstorms imply that the updraft in the mother thunderstorm is offset from its downdraft. New cells usually form in the upwind (usually western or southwestern) part of the storm where the downdrafts of the mature cells meet the environmental wind, lifting air parcels and triggering new convection. The mature cells are thus usually in the center of the storm, and dissipating cells are usually in the downwind (usually eastern or northeastern) part of the storm.

Characteristics

The multicellular cluster can last for hours while each individual cell should only last for about 20 to 60 minutes. These storms can sometimes be severe and sometimes have awkward paths due to the thunderstorm sometimes not following the path of the cells that compose it. The typical hodograph, plot of the wind versus altitude, associated with it shows a linear wind shear with altitude The moderate vertical wind shear leads to the development of a non-symmetric surface convergence associated with the thunderstorm outflow, with the strongest convergence taking place on the downwind side from the storm's motion. So while individual cells move along the windshear, the line moves at 30° of it, at 70% of the mean wind speed in the layer.

The Convective available potential energy (CAPE) is moderate to large, usually between 800 and 1,500 J/kg. The radar structure of this type of thunderstorm is characterized by overhangs of reflectivity in the southwestern part of the cluster.