The Bay low due today could become a depression by 15 November, yet the Met centre expects below-normal rain in Tamil Nadu until 26 November.
The numbers
A depression by Sunday. That is the new line in the Regional Meteorological Centre (RMC) Chennai extended range forecast issued on Thursday 12 November.
The low pressure area is still expected to form over the southeast Bay of Bengal around today, 13 November. The RMC now says it is likely to become more marked on 14 November and to deepen into a depression over the central parts of the south Bay around 15 November. Forecast models agree that the system could intensify into a cyclonic storm, the bulletin says, but their tracks and landfall points diverge in the second week. Nobody at the Nungambakkam office is putting a coastline on it yet.
For Chennai (சென்னை) and the rest of the state, the same bulletin reads drier than the headlines. Rainfall is likely to be below normal over most of Tamil Nadu, Puducherry and Karaikal in week one (13 to 19 November) and week two (20 to 26 November). Temperatures should stay generally normal.
The last week fell a third short
| Period | Actual | Normal | Departure |
|---|---|---|---|
| Week, 5 to 11 November | 34.7 mm | 51.7 mm | -33% (deficient) |
| Season, 1 October to 11 November | 259.1 mm | 254.2 mm | +2% (normal) |
Source: RMC Chennai extended range forecast, 12 November 2026 (Tamil Nadu, Puducherry and Karaikal subdivision).
Of the 40 districts in the subdivision, 17 were deficient last week and 12 more were largely deficient.
The season total still sits at +2% because October did the heavy lifting. Eleven districts remain in excess for the season.
What the Thursday bulletins showed
The RMC regional report issued at 2 pm on Thursday carried no rain or thunderstorm warning for Tamil Nadu. It forecast isolated rain over the state on every day to 18 November, and placed upper-air cyclonic circulations over the Gulf of Mannar and the southeast Arabian Sea. Kurunthancode in Kanyakumari district topped the state with 4 cm in the 24 hours to 8.30 am, followed by the Neyveli automatic weather station in Cuddalore district with 3 cm, while Pamban and Tarangambadi managed 1 cm each.
At sea, the picture is further out. The Area Cyclone Warning Centre coastal bulletin issued on Thursday night listed the synoptic system as nil and forecast northerly to northeasterly winds of 10 to 15 knots along the north Tamil Nadu coast, gusting to 25 knots, with the sea moderate and turning rough in gusts. No port signal was hoisted.
The fishermen warning issued at 8.30 pm on Thursday flags squally weather, 40 to 50 km/h gusting to 60 km/h, over the Andaman Sea and many parts of the southeast Bay on 13 and 14 November. On 15 and 16 November the winds rise to 45 to 55 km/h, gusting to 65 km/h, over parts of the southeast and adjoining southwest Bay. Fishermen are told not to venture into those areas. The State Department of Fisheries and Fishermen Welfare had already asked boats on the east coast to be back in harbour by Thursday night and said no fishing tokens would be issued from today.
The latest city forecast on the RMC site, issued on 11 November, gives Chennai a partly cloudy sky with light rain in some areas today, 31 to 32 degrees Celsius by day and 24 to 25 at night. It moves to light to moderate rain in some areas from 15 to 17 November.
How we worked this out
All figures are from RMC Chennai bulletins opened on 13 November: the extended range forecast and regional report of 12 November, the coastal bulletin of 12 November (1500 UTC), the fishermen warning of 12 November and the city seven-day forecast of 11 November, the newest city forecast posted. Departures are the RMC’s own. The fishing-token advisory is the State Fisheries Department’s.
For Context
The 11 November RMC bulletin had said the low could become a well-marked low within 24 hours of forming and gave Chennai, Tiruvallur, Chengalpattu, Kancheepuram and Ranipet districts moderate rain at isolated places on 16 and 17 November. The next extended range forecast is due on 19 November.
Checked against official sources on 13 November 2026.
Sources
- Extended Range Forecast, Regional Meteorological Centre Chennai, issued 12 November 2026
- Regional Daily Weather Report, RMC Chennai, 12 November 2026, 1400 hrs IST
- Coastal Weather Bulletin, Area Cyclone Warning Centre Chennai, 12 November 2026
- Fishermen Warning, RMC Chennai, 12 November 2026, 2030 hrs IST
- Chennai City 7-day Forecast, RMC Chennai, 11 November 2026
