Even as the country is awaiting the onset of southwest monsoon, the signs of a cyclonic circulation over the Arabian Sea have put a question mark on the initial performance of the monsoon over Kerala and along the west coast.
Though monsoon clouds are visible over Kerala ahead of the onset date of June 4 forecast by the India Meteorological Department (IMD), weather models of various global agencies such as the European Centre for Medium Range Weather Forecast (ECMRWF), Global Forecast System (GFS) etc., have provided enough hints of cyclone over the Arabian Sea by next week.
IMD senior scientist D. Sivananda Pai says though the signs of cyclonic circulation are visible over the Arabian Sea, there is no certainty it will intensify into a severe cyclonic storm affecting the prospects of the monsoon or increase rainfall along the west coast.
“There will be some clarity on the system and its path in the coming days if it develops further. In case the system develops and moves in north-west direction, the prospects of heavy onset will be affected. On the other hand, if it moves northward along the west coast and takes a recurve influenced by a monsoon trough, there will then be intense spells along the west coast, including Kerala,” he adds.
Meanwhile, the monsoon has reached southern Arabian Sea and is likely to knock at the door of Kerala within two or three days.
According to another IMD scientist, it is a voyage of winds from Mascarene High off the coast of Madagascar to Indian continent, transcending borders, various geographical regions in South Asia and cultures. It is a south-easterly in the southern hemisphere and it takes the direction of south-westerly when it crosses the Equator due to the influence of coriolis forces developed owing to the rotation of the earth.
In fact, the Somali jet stream pushes the monsoon current towards India. Before reaching India, the monsoon winds branch into two - Arabian Sea branch and Bay of Bengal branch. The Arabian Sea branch again splits into three branches – one branch climbs the slopes of the Western Ghats bringing copious rain in Kerala, while the other two branches strike the north coast of Mumbai along Narmada and Tapti river valleys and Saurashtra-Kachchh respectively.
On the other hand, the Bay of Bengal branch strikes the coast of Myanmar and parts of south-east Bangladesh and later the Indian subcontinent after splitting into various branches. One of the branches will then reach up to Punjab joining the Arabian Sea branch and will reinforce each other, causing rain in western Himalayas. The formation of cyclone over the Arabian Sea will affect only the Arabian branch of the jet stream, while the Bay of Bengal branch will be intact, he says.
