Figure 29 – life cycle of a extra-tropical cyclone

There is great degree of variation in shape and size of extra-tropical cyclones. Generally, the isobars are almost circular or elliptical. However, in certain depressions, the isobars take the shape of the letter ‘V’. Such storms are called V-shaped depression. At times, the cyclones become so broad and shallow that they are referred to as troughs of low pressure.