Mechanism of Easterly Jet Steam and Tropical Cyclones in the Summer Season in Indian Subcontinent
The subtropical jet stream is located approximately 13 kilometers above the subtropical high-pressure zone. The easterly jet stream streams the tropical depressions into India. These depressions play a significant role in the distribution of monsoon rainfall over the Indian subcontinent. The tracks of these depressions are the areas of highest rainfall in India. The frequency at which these depressions visit India, their direction and intensity, all go a long way in determining the rainfall pattern during the southwest monsoon period. The easterly jet does not come into existence if the snow over the Tibet Plateau does not melt. This hampers the occurrence of rainfall in India. Therefore, any year of thick and widespread snow over Tibet will be followed by a year of weak monsoon and less rainfall.
Tropical Cyclones in Summer Season
Tropical cyclones originate in the Bay of Bengal and the Arabian Sea. A few cyclones are formed in the Bay of Bengal in the month of March but they do not affect the mainland of India.
Their frequency rises steeply in April and the number of cyclones originating in May is more than double than those originating in April.
About three-fourths of the tropical cyclones are born in the Bay of Bengal and the rest originate in the Arabian Sea.
Most of the depressions in April originate to the south of 10°N while those originating in May are born to the north of this latitude.