With the southwest monsoon officially ending in Kerala, the India Meteorological Department (IMD) has forecasted above normal rainfall across the State during the northeast monsoon season.
As of now there is a transition period from westerlies to easterlies that normally takes place immediately after September. However, the State is likely to receive light to moderate showers triggered by westerlies as the westerlies are likely to prevail over the State at least for the next 10 days. Only after the complete withdrawal of the monsoon will the northeast monsoon, powered by easterlies, set in over the State.
The average rainfall over the South Peninsular India consisting of Tamil Nadu, Puducherry, and Karaikal, coastal Andhra Pradesh, Rayalaseema, Kerala, and Mahe, and south interior Karnataka during the northeast monsoon is most likely to be above normal (>112% of Long Period Average) during post-monsoon season (October-December, 2024), said the IMD in its long-range forecast.
The State used to receive around 492 mm of rain during the northeast monsoon and witnessed a 27% excess rainfall in the previous year. On the other hand, the southwest monsoon drew to a close in Kerala on a positive note, although the extreme rainfall events in July left a trail of destruction and catastrophic landslides in Wayanad, claiming hundreds of lives. Despite the extreme rainfall events at the fag end of July, the southwest monsoon is around 13% deficient in Kerala. However, the season is considered normal considering the margin of error in the performance of the monsoon. IMD considers a deviation in rainfall up to 19% either deficit or excess as normal range.
During the four-month southwest monsoon, only July witnessed above normal rainfall, while the rainfall was deficient in the June, August, and September months. July accounts for the highest amount of rain in Kerala followed by June, August, and September. The surplus rain in July helped the State bridge the deficit, despite around 30% shortfall of rain during the other three months.
As for the large scale features, La Niña phenomenon, which is associated with excess rainfall in India, is yet to take shape in the Pacific Ocean. The Bureau of Meteorology (BoM), Australia, in its latest update released on Tuesday is not decisive on the formation of weather pattern. The bureau’s model suggests sea surface temperatures (SSTs) are likely to remain within the ENSO-neutral range throughout the forecast period to February 2025.
The Indian Ocean Dipole (IOD) is currently neutral, with the weekly IOD index of −0.39 °C (as of 29 September). Most of the models indicate that the IOD is likely to remain neutral, but weakly negative, for the rest of the year. An IOD event that enhances rainfall activity in parts of India is also unlikely, according to BoM.
Published - October 01, 2024 11:05 pm IST
