Cyclone affecting the monsoon’s onset

(MainsGS1:Important Geophysical phenomena such as earthquakes, Tsunami, Volcanic activity, cyclone etc.)

Context:

• The impact of global warming on the monsoons are manifest in the onset, withdrawal, its seasonal total rainfall, and its extremes. 
• Global warming also affects the cyclones over the Indian Ocean and the typhoons over the northwestern Pacific Ocean.

Impact of cyclone’s position:

• Some cyclones in the North Indian Ocean have had both positive and negative impacts on the onset of the monsoon. 
• Since the circulation of winds around the cyclones is in the anticlockwise direction, the location of the cyclone is critical as far as the cyclone’s impact on the transition of the monsoon trough is concerned. 
• For example, if a cyclone lies further north in the Bay of Bengal, the back-winds blowing from the southwest to the northeast can pull the monsoon trough forward, and assist in the monsoon’s onset.
• Earlier this year, the Bay of Bengal had Cyclone Mocha develop in the first half of May and intensify briefly into a ‘super cyclonic storm’, before weakening rapidly upon landfall. 
• Mocha’s northwest to east trajectory over the Bay was the result of unusual anticyclones (which rotate clockwise) that have been parked over the Arabian Sea and the Bay of Bengal since March. 
• Mocha dissipated on May 15 and the back-winds helped the monsoon set in on time over the Andaman and Nicobar Islands.

 Monsoon trough:

• The strong southwesterly winds over the Bay of Bengal can be imagined to be a very large highway with heavy traffic heading from the southwest, over southern peninsular India and Sri Lanka, towards the South China Sea and the northwestern Pacific Ocean, feeding the monstrous typhoons there. 
• The monsoon trough in the meantime is like a little car trying to cross this busy and wide highway from the Andaman Nicobar Islands to India across the Bay of Bengal.
• This complicated dance of global warming affects cyclogenesis over the Pacific and North Indian Oceans and in the predictions of the monsoon’s onset and its evolution through the season. 
• Once seen as a very reliable system, with its annual migration northwestward and the withdrawal southeastward, the monsoon trough is now being kicked around in the game of climate-change.