The southwest monsoon withdrew from the entire country on Thursday, the India Meteorological Department said, noting that northeast monsoon rainfall activity commenced over parts of south India on the same day.
Tamil Nadu, Puducherry, Karaikal, coastal Andhra Pradesh, Rayalaseema, south interior Karnataka, Kerala and Mahe witnessed activity under the northeast monsoon, the department added. The Press Trust of India reported the announcement in a dispatch carried by The Hindu.
"With the onset of the northeast monsoon, a wet spell with isolated heavy falls is likely over many parts of south peninsular India till October 21," it said in its daily forecast.
India has two notable monsoons. The southwest monsoon is active from June to September. The northeast monsoon, also known as the retreating monsoon, affects parts of the country from October to December and is the less intense of the two.
The distinction matters to the farming calendar. The southwest monsoon plays a crucial role in the country's economy, especially through its direct impact on the kharif crop cycle. The northeast monsoon is significant for the growth of rabi crops.
This year's southwest monsoon ended with 759.4 mm of rain, 12.6 per cent below the normal of 868.6 mm, according to the IMD.
One key reason behind the rainfall deficit has been the prevailing El Niño conditions over the tropical Pacific, which emerged in June and have been gaining strength since. El Niño is known to reduce monsoon rainfall over India.
El Niño, which is known to have a warming effect over the planet, is one phase of a cycle whose opposite phase, La Niña, usually results in a cooling effect. The cycle also has a neutral phase, which is the one that attracts no announcements at all.
The dates repay a careful reading. A season officially active from June to September was declared over on 15 October, which is in neither month. The season that replaced it is named for retreating, and it advanced.
Taken together, the two announcements describe a country in which the rains left and the rains arrived at the same moment, in opposite directions, and the meteorological record will show both as having happened on Thursday.
The nomenclature is doing a great deal of work here. A rain-bearing system called the retreating monsoon has set in over eight named regions, where it is expected to produce isolated heavy falls until 21 October. Any reader attempting to follow the position by name alone will conclude that southern India is being rained on by a withdrawal.
The rainfall accounting observes the same conventions. The southwest monsoon delivered 759.4 mm against a normal of 868.6 mm, a shortfall of 12.6 per cent. That shortfall is measured over a season whose stated span is June to September and whose actual span, this year, ran a fortnight into the month after it.
Our analysts have attempted to establish which of Thursday's two events the eight named regions experienced and have concluded that they experienced both. The withdrawal was national and complete. The onset was regional and wet. Neither announcement contradicts the other, which is the difficulty.
The Department of Unnecessary Research briefly proposed that the June-to-September monsoon be renamed the June-to-October monsoon, and withdrew the proposal on the grounds that it would then be due to withdraw in November.
South peninsular India is accordingly forecast a wet spell with isolated heavy falls until 21 October, courtesy of the system that began by leaving.