
The northeast monsoon is officially ‘over’ for South India, as of 31st Dec 2024. However, equatorial oceanic disturbances remain a regular feature for the subsequent 2-3 weeks. Earlier, a cyclonic circulation was marked over Sri Lanka and adjoining parts. This system caused rain and thundershowers all along the Tamil Nadu Coast and in a few places in the interior region as well. The system has since moved over the Comorin area as a broad cyclonic circulation with trough extension to the north across the interiors of the Peninsula.
This is a slow-moving system and will affect the South Peninsula for three more days between the 13th and 15th of January 2025. Accordingly, it will lead to a rainy Lohri, Pongal and Makar Sankranti over most parts of Tamil Nadu, Kerala, South Coastal Andhra Pradesh, Rayalaseema, South Interior Karnataka and Kerala. Rainfall is going to be light to moderate. However, isolated heavy rainfall is expected during this period.
This weather system will move across Maldives and Lakshadweep region over the subsequent two days, on 16th and 17th Jan. The southern states will find a break in the weather activity during this period. Coastal Tamil Nadu may continue to have light rains, even on these two days. Another equatorial circulation is likely to come up over extreme Southeast and Southern Parts of Central Bay of Bengal on 16th Jan. Actually, an active Madden-Julian Oscillation (MJO) is propagating eastward and is positioned in the proximity of the South Indian Ocean, accentuating the frequency and scale of weather activity. The circulation over the Bay will move eastward across Sri Lanka and reach the vicinity of Coastal Tamil Nadu on 18th Jan.
Fairly widespread rain and thundershower activity is expected to lash the states of Tamil Nadu and Kerala between the 18th and 20th Jan. Though, the spread of weather activity will remain confined to the southern parts of the states, the intensity will be strong enough to cause heavy to very heavy rainfall. The places at risk will include Ramanathapuram, Thoothukudi, Tirunelveli, Kanyakumari, Tondi, Pamban, Tuticorin, Thiruvananthapuram, Alappuzha and Kollam. Yet another weather system as cyclonic circulation will follow after a gap of 3 days. Since the model accuracy goes low after about 4-5 days, the reliability and confidence level of the forecast is low for this period.