The low pressure area over the Bay of Bengal will intensify as Chennai braces for heavy rainfall due to the impact of severe Cyclone Ditwah. | Photo credit: B. Jothi Ramalingam
Cyclone Ditwah and its remnants stalled and moved slowly for several hours as they got stuck in a calm “col” zone between two opposing anticyclonic circulations in the upper atmosphere, resulting in prolonged rains, meteorologists noted.
Although the system was expected to move away from the TN coast by Monday (December 1, 2025), it remained stationary for a few hours, absorbing more moisture and generating new bands of rain-bearing clouds that hit a stretch near Tiruvallur and Chennai, they said.
Read: Cycle Ditwah LIVE updates
B. Amudha, Head (Additional Charge), Regional Meteorological Centre, said the system, which had settled between two anticyclonic circulations, was oscillating under the push and pull of surrounding winds. “It is difficult to predict such microphysical changes that happen continuously in the atmosphere well in advance, and rapid changes can only be observed over short periods. Interactions between land, ocean and atmospheric changes contribute to cloud dynamics in a complex way. Our understanding of the internal dynamics of tropical cyclones is incomplete,” she said.
Meteorologists noted that predicting such behavior in the tropics is challenging, especially because weather models have limitations. Sometimes weather models fail to predict when weather systems will stop moving.
YEA Raj, former Deputy Director of Meteorology, Chennai, said Cyclone Ditwah was a marginal cyclone with wind speed reaching up to 40 knots. The noticeable slowdown of the system was unexpected and the movement was slow at 2-3 km/h.
Depressions or cyclones usually slow down before turning back. This system was returning towards the southwest instead of the usual north or east direction, which is rare for tropical cyclones. As they move north, the systems will pick up speed.
During the period between 1981 and 2024, only three weather systems turned back and moved towards the southwest in November 1996, November 2013 and December 2018, he added. The delay in precipitation was due to the vagaries of the weather as the behavior of the system was affected by rapidly changing atmospheric conditions.
Published – 02 Dec 2025 20:46 IST
