This depression has produced very heavy rainfall across much of Sri Lanka and into the far south of India over the weekend. The capital of Sri Lanka, Colombo, reported 305mm of rain on Sunday (May average rainfall is 371mm), leading to some flooding impacts.
The tropical depression is expected to move northwards this week, probably close to the eastern India coastline, bringing unusually early heavy rainfall up the eastern coast of India. As the system tracks north, up to 400mm of rain is possible in a 24-hour period. For reference, Chennai has an average May rainfall of only around 25mm, but residents could see over 10 times this in a 24-hour period for a time this week.
In the wake of this tropical system, a very moist west-to-southwest flow will persist across Sri Lanka and the far south of India; most likely bringing further heavy rainfall across populated areas of Sri Lanka. There is a risk of a further 600mm, on top of the weekend’s rainfall, in Colombo which could lead to serious flooding.
There is a risk that this tropical depression could strengthen to produce tropical storm-force winds as it tracks north this week, but the main impacts are likely to come from the very heavy rainfall.
Tropical depressions and storms in the North Indian Ocean in May are not particularly unusual. They usually occur in the pre-monsoon period (April to June) and post-monsoon period (October to December). However, this tropical depression is likely to produce greater impacts than most due to its formation close to Sri Lanka and projected track along the length of the eastern coast of India.