“Chennai sky has turned grey again with the dark clouds hovering over” and the city and neighbouring coastal districts will come under a Yellow Alert issued by The India Meteorological Department (IMD). After heavy rain this week, there is no ready relief yet from the fury of the monsoon, leaving residents to trudge through waterlogged roads and brace for worse.
The alert indicates that the incessant showers are due to a robust system emerging from the Bay of Bengal, which is furiously stimulating and pushing in moisture rich winds onto TN coast. And the question we all want answered is equally straightforward: When will this ceaseless cycle of showers come to an end?
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The Instant Danger: Yellow Alert and Rainstorm Prediction
The IMD Yellow Alert issued for Chennai indicates a possibility of isolated heavy to very heavy rainfall in the city over the next 48–72 hours. It is not as serious as the Red Alert, which signifies widespread damage or disruption and the risk to life is likely, but is more serious than an amber alert that warns people to be prepared for adverse weather.
The Dynamics of the Downpour
The present spell is ascribed to an LPA which has intensified into a WMLA over SW BoB off Sri Lanka and TN coasts.
WMLA Impact: This WMLA is a giant atmospheric pump and can be considered as a reinforcement force to the NE monsoon flow. It sucks in huge quantities of moisture, sending thick clouds inland and drenching the coastal plains with heavy rain.
Intensity forecast: According to the IMD outlook, isolated locations in Chennai and other districts such as Tiruvallur, Kancheepuram and Chengalpattu may experience rainfall of about 100 millimetres (mm) or more during a 24-hour period.
Short Term Effects: The immediate danger will be waterlogging in low-laying localities like Velachery, Tambaram and Mylapore being the core areas of Chennai which could cause havoc right from jamming traffic as well as day-to-day live-in lifestyle.
The Clearing Horizon: How Long Will the Monsoon Last?
The release of the new satellite imagery and meteorological models has provided a clear schedule for when rainfall will slow, and hope for an end in sight for weary citizens.
Phase 1: Nonstop Rain (Until Dec. 7)
The worst of the spell is expected to peak on Friday and Saturday (6–7 December). The WMLA is foreseen to move slowly along the Pacific coastline over this time frame and maintain high rainfall events. Schools and colleges in a few districts will not function or will run with reduced timings.
Stage 2: The Cut and the Wheel (December 8–9)
The key change is likely to come soon, around Dec. 8 Sunday. While WMLA is expected to gradually turn away from the coast of Tamil Nadu (it should weaken or dissipate) moisture influx in the form of heavy rain would taper.
Forecast for change: Rainfall intensity is expected to decrease to light–moderate showers with isolated heavy spells. The ceaseless all-day drizzle should give way to some on-and-off showers.
Stage 3: Arrival of the Clear Sky Signal (Dec 10 and beyond)
Messy long-range models indicate a marked decline in the heavy rain past about Tuesday 10th December.
Relief: Come beginning of next week, it’ll be mostly cloudy with negligible to no rains in Chennai. This is likely the end of current big spell with WMLA. But isolated, light showers of the kind typical of Northeast Monsoon could still continue occasionally.
The city corporation and disaster management authorities have been instructed to make best use of this evident window of weather opportunity to expedite the draining works, clear the blockades, and return normalcy before another probable monsoon system appears later in the month. For the time being, city residents have been advised to follow IMD advisories, and stay at home as far as possible, taking all appropriate precautions against further heavy rain.
