Fast flowing and narrow air currents are called jet streams. The streams flow at high altitudes (about 12,000 feet) in the troposphere. The westerly jet streams are responsible for western cyclonic disturbances in the north and north-western parts of India. The subtropical westerly jet stream moves north of the Himalayas with the apparent movement of the sun. The tropical jet stream (an easterly jet stream) blows over the Indian Peninsula; approximately over 14° north during the summer months.
