The India Meteorological Department (IMD) has found that the global models are forecasting an increase in rainfall activity over the Tamil Nadu coast during the next 4-5 days. During this period, Kerala and Tamil Nadu are expected to get widespread to widespread mild to moderate rainfall, with occasional intense rainfall.
From November 26 to 28, the South Peninsula will get widespread to widespread light to moderate rainfall, with isolated heavy showers possible in South Coastal Andhra Pradesh and North Tamil Nadu.
In what is typically a progression of a sustained wave of rain along almost a straight line over the seas and the islands on both sides of the South Peninsula, but mostly confined to the states of Tamil Nadu and Kerala over the mainland, scattered light to moderate rainfall is also predicted over the Andaman & Nicobar Islands and Lakshadweep area
Easterly wave at work
During the North-East monsoon, easterly waves frequent the Bay of Bengal, creating this effect. An easterly wave is a migratory wave-like disturbance inside the wide easterly current that goes from East to West (as opposed to a western disturbance in the north of India from West to East) and moves at a slower rate than the current in which it is embedded.
The current one, as noted by IMD on Sunday evening, comprises of a cyclonic circulation, although being best defined in terms of its wave-like properties in the wind field. In the past, easterly waves would hit the seas one after the other and some would go on to create low-pressure regions, depressions, or even cyclones in the South Bay of Bengal.
Potent rain-head upfront
They carry a 'rain-head' in front of them that explodes over the Sri Lankan or Tamil Nadu coasts, but also extend rains in Kerala, the Lakshadweep Islands, and the Arabian Sea. As a result, the impending wave will bring a new round of rain to the South Peninsula, which is currently recovering from heavy rain carried inland by a Bay depression.
Coastal Andhra Pradesh, Rayalaseema, Telangana, Karnataka, Tamil Nadu, Puducherry, and Kerala had severe to very heavy rainfall in the 24 hours leading up to Sunday morning, as well as high rainfall in isolated spots.
