After the revival of the southwest monsoon for over a week in September, the intensity of rain is set to come down in the State.
Kerala witnessed an average of 136 mm of rainfall in the first nine days of September. August had registered a monthly rainfall of only 59.6 mm, the lowest monsoon precipitation in 123 years in Kerala.
The late surge was aided by a low pressure area over the Bay of Bengal and the subsequent shifting of the monsoon trough — an elongated low pressure zone from the heat low of northwest India with its axis running parallel to the Himalayan mountains in a west-to-east direction — southwards of its normal position.
Now the weather systems over the Bay of Bengal have weakened and the monsoon trough is back to Jaisalmer on the west and the eastern side shifting between north Bay of Bengal and central Bay of Bengal.
According to Indian Meteorological Department sources, the position of the monsoon trough triggered the renewed spell in Kerala. When the trough moves downward, rain will gain strength and wane when it shifts upward. With the trough back to its normal position, rain intensity is set to decrease in the State from Monday.
“Though there will be a temporary cessation of rainfall activity over Kerala by the first of next week, we hope there will be one more renewed spell before the withdrawal of the southwest monsoon — the normal date of withdrawal from Rajasthan and neighbourhood starts from the third week of September,” says Madhavan Rajeevan, former Secretary, Union Ministry of Earth Sciences.
A low pressure area may form by the middle of this month that may again bring the monsoon trough southwards of its normal position. If this happens, Kerala will get another late surge before the withdrawal of monsoon, which is still 43% in deficit, says Mr. Rajeevan.
The inflow in the major reservoirs under the Kerala State Electricity Board (KSEB) has witnessed a record low from June 1 to August 31, with Idukki receiving an inflow of 451 mcm (46%) against the long-period average of 975 mcm, Kakki 53%, Idamalayar 41.9%, and Banasura Sagar 56%.
September normally contributes around 10% of water to the reservoirs of the 80% contributed by the four-month southwest monsoon season.
