Conceptual model of a Mesoscale convective complex (MCC)

A mesoscale convective complex (MCC) is one kind of mesoscale convective systems. They are very long living systems with partly extreme weather conditions like heavy rain, hail, gusts.

MCCs are often the final stage of a convective development (single cells, multi cells, squall line). MCCs were often observed during the night. After sun rise they start weakening. Its definition is based upon IR-images.A MCC has an area of at least 100,000 kmē of less /equal -32°C and an area of at least 50,000 kmē with cloud top temperatures of less/equal -52°C. These conditions have to last without any interruption for at least 6 hours.

Near the surface the MCC exhibits in his centre relatively high pressure due to the cold air. At his leading edge an outflow boundary can be found. In the mid level a cyclonic rotation is common. In the upper troposphere an anticylonic rotation and a divergence can be seen. The divergence in upper levels and the convergence near the surface result in upward motion. This yields the long lifetime of an MCC.