A family uses a boat to reach the main road after the premises of their house got inundated in heavy rain at Mankombu in Kuttanad, Alappuzha on May 29, 2024.
| Photo Credit: Suresh Alleppey
After a harsh and eventful summer, Kerala is all set for the southwest monsoon on May 30 (Thursday), two days ahead of its normal onset.
Southwest monsoon usually sets in over Kerala around June 1 and progresses northward in surges, covering the entire country around July 15. The India Meteorological Department (IMD) on Wednesday announced that the southwest monsoon will arrive in Kerala in the next 24 hours.
Among the three major criteria set for the declaration of monsoon over Kerala, two criteria — rainfall over 14 stations in Kerala and neighbouring areas should record over 2.5 mm for two consecutive days and the Outgoing Longwave Radiation (OLR) should be below 200 wm-2.
These two criteria were met, while the third criterion, the depth of the westerly winds, which should be up to 600 hPa, indicating the strength of the monsoon winds, was not met on May 29 (Wednesday).
Westerly winds should prevail up to 4.5 km in height in the atmosphere. But it is assumed that it would be met by May 30 (Thursday), considering the prevailing conditions.
When the three-month-long summer season gave way to monsoon, Kerala also witnessed some of the unusual weather events that the State was not familiar with. For the first time in the history of Kerala, a heatwave was confirmed.
Though the heatwave alert was issued for various districts during the peak summer, only Palakkad realised the heatwave on April 25, 26, 27, 28 and 29. For confirming a heatwave, the temperature should be above 40°C with a departure of 4.5°C or more from the normal temperature.
Palakkad also reported more than 40°C on 16 days out of 46 days from April 1 to 16. Though Thiruvananthapuram met the criteria for a heatwave one day on May 8, it was not announced as the two consecutive-day criteria were not met.
The temperature was also met in Thrissur (April 29), Alappuzha (April 29, May 6 and 8), and Punalur May 8, but not for two consecutive days.
In Alappuzha, warm night conditions were realised on May 3 and 4 with the maximum night temperature touching over 37°C and departure from the normal recording of 4.5°C and above.
Also, the last two weeks of May also witnessed record summer rain in Kerala with the excess rain triggered by the cyclonic circulations over the Arabian Sea and the cyclone in the Bay of Bengal wiping out the rain deficit in the summer season.
Now, the monthly and seasonal forecast issued by the IMD for June and the entire four-month season warns of above normal rainfall in Kerala.
