High Quality Content by WIKIPEDIA articles! Extratropical cyclones, sometimes called mid-latitude cyclones or wave cyclones, are a group of cyclones defined as synoptic scale low pressure weather systems that occur in the middle latitudes of the Earth (outside the tropics) having neither tropical nor polar characteristics, and are connected with fronts and horizontal gradients in temperature and dew point otherwise known as "baroclinic zones". Extratropical cyclones are the everyday phenomena which, along with anticyclones, drive the weather over much of the Earth, producing anything from cloudiness and mild showers to heavy gales and thunderstorms.