These are fast blowing winds of a steady velocity moving in a narrow zone of the upper layer of the atmosphere.
Their speed varies from about 110 km/h in summer to about 184 km/h in winter. Jet streams are located approximately over 27°-30° north latitude, therefore, they are known as subtropical westerly jet streams. A number of separate jet streams have been identified. The most constant are the mid-latitude and the sub tropical jet stream. The western cyclonic disturbances experienced in the north and north-western parts of the country are brought in by this westerly flow.
