Monsoon remains largely subdued in Kerala, La Niña emergence may be further delayed

Though Kerala is likely to receive some isolated heavy showers, especially in its northern and central parts for the next few days, the southwest monsoon is likely to remain in a subdued mode in the State at least for the next week. Although the monsoon trough, a low-pressure zone that runs parallel to the Himalayan Mountains from North-West India to the Bay of Bengal, is active, it lies near its normal position and it is likely to continue so for the next 4-5 days.

When the monsoon trough moves south of its normal position, it used to trigger heavy rain in the north-west, central and eastern regions of the country. Further, the vertical offshore trough that runs along the west coast during the monsoon period now runs along the south Gujarat-north Kerala coasts favouring heavy spells in the core monsoon regions along the west coast, including coastal Karnataka, Goa, Maharashtra, parts of Gujarat and north Kerala.

However, the State will have to wait further to get some major spells, except in some areas in north Kerala, as per the current synoptic conditions. The moderate rainfall the State is likely to get for the next few days is largely due to the moist wind blowing in from the Arabian Sea and the Bay of Bengal to the different pressure gradients over the land.

Meanwhile, the Bureau of Meteorology (BoM), Australia, in its latest update made clear that the majority of its climate models suggest the possibility of sea surface temperatures (SSTs) in the central Pacific Ocean reaching the La Niña threshold (below −0.8 °C) only by October. Compared to earlier forecasts from global agencies which hinted at the emergence of La Niña around July, the potential for La Niña development, the natural phenomenon that used to bring copious rain to India, will be by spring. Further, the Indian Ocean Dipole (IOD) is currently neutral. The latest model outlooks indicate that the IOD is likely to remain neutral until at least the end of winter, according to the BoM. The positive phases of the dipole normally tend to be favourable for good monsoon for the State and the country in general.

The delay in the emergence of La Niña and IOD turning positive is likely to favour a normal monsoon season this year, according to senior scientists in the IMD. In contrast, the national agency had forecast an above normal monsoon season this year.

Yellow alert

Meanwhile, the IMD has issued a yellow alert for seven districts — Ernakulam, Thrissur, Malappuram, Kozhikode, Wayanad, Kannur and Kasaragod, on Thursday warning of isolated heavy rain.