mesoscale convective complex

(Abbreviated MCC.) A subset of mesoscale convective systems (MCS) that exhibit a large, circular (as observed by satellite), long-lived, cold cloud shield.

The cold cloud shield must exhibit the following physical characteristics.

Size: A - Cloud shield with continuously low infrared (IR) temperature ≤ -32°C must have an area ≥ 10⁵ km²; and B - Interior cold cloud region with temperature ≤ -52°C must have an area ≥ 0.5 X 10⁵ km².

Initiate: Size definitions A and B are first satisfied

Duration: Size definitions A and B must be met for a period ≥ 6 h.

Maximum extent: Contiguous cold cloud shield (IR temperature ≤ -33°C) reaches maximum size.

Shape: Eccentricity (minor axis/major axis) ≥ 0.7 at time of maximum extent.

Terminate: Size definitions A and B no longer satisfied.
Alternatively, a dynamical definition of an MCC requires that the system have a Rossby number of order 1 and exhibit a horizontal scale comparable to the Rossby radius of deformation. In midlatitude MCS environments, the Rossby radius of deformation is about 300 km.

1. In general, a broad cloud formation that is not more than four times as long as it is wide.

In connection with wind waves, the duration is the length of time that winds generating surface waves have been present.

Any function of time f(t) is periodic with period t if f(t) = f(t + τ) for all times t, where τ is the smallest number for which this equality holds.

1. The distance that cold pools of air can spread under the influence of the Coriolis force.