Though its onset has been declared over the southern peninsula, Kerala will have to wait a few more days to witness the thunderstorms associated with northeast monsoon, also known as Thulavarsham in the State.
The India Meteorological Department (IMD) has simultaneously declared the withdrawal of southwest monsoon along with the onset of northeast monsoon.
However, the light to moderate and isolated rain spells the State has been receiving in the past few days appear to be associated with the features related to the withdrawal of southwest monsoon.
Ahead of the establishment of the easterlies (northeast monsoon wind) associated with the Thulavarsham, the Intertropical Convergence Zone will move towards the southern hemisphere. During the southwest monsoon period, it will merge with the monsoon trough. After the season, it will move gradually downward and go below the equator facilitating the establishment of the northeast monsoon winds.
This movement reduces the rain in northern States gradually, and once it goes below 15 degrees north, northeast monsoon is likely to commence. The present synoptic conditions reveal that complete withdrawal of southwest monsoon has not happened, and easterlies are yet to be established with the full vigour of the season.
At present there is only circulation in the Bay of Bengal, and once the circulation is detached it will be clear, sources say. The cyclone formed in the Bay of Bengal has also helped trigger the rain along the east coast. After the dissipation of the cyclone, the easterlies are likely to gain strength, say the sources.
Typically, northeast monsoon brings rain in spells, often heavy short spells accompanied by lightning and thunderstorms, while uninterrupted rain is one of the main characteristics of southwest monsoon.
Meanwhile, the IMD has issued a yellow alert warning of isolated heavy rain for Pathanamthitta, Alappuzha, Kottayam, Ernakulam, and Idukki on Thursday fuelled by an upper air cyclonic circulation over the Comorin area and the cyclone over the Bay of Bengal.
Published - October 23, 2024 07:20 pm IST
