Cyclone is simply the generic name for a large rotating air mass. It is a barometric depression or LOW and is characterized by a flow of air inward and around a moving centre. The air circulation is counter-clockwise in the northern hemisphere and clockwise in the south.

Perhaps if the earth stopped rotating and there was no planetary circulation, with the great west-moving trades and east-moving "westerlies," the arrows on the weather map would all point directly toward the centre of the LOW; but, as things are, there are some very good reasons why air can not move directly into a LOW, that is at right angles to the isobars.

Moreover, the weather map does not indicate the true flow of the air, for observations of the wind made at the ground tell only a part of the story of the balance which the flowing air must maintain under the action of various forces, such as gravitation, rotational deflection, centrifugal tendency, and the various expansion and compression forces.

The winds near the ground are modified both in velocity and direction by friction. The free flow is often interfered with by topography.