Extratropical cyclone; polar-front model; cyclogenesis কী?

An extratropical cyclone is a cyclone of the middle and high latitudes, often some $2000\,\mathrm{km}$ across, which usually contains fronts, a cold front trailing for hundreds of kilometres towards the equator. The polar-front model describes its life as a wave that grows on the polar front, the long front between polar and tropical air. Cyclogenesis is the formation or the intensification of a cyclone.