Highlights

Cyclone Arnab

A low-pressure area is currently developing over the Bay of Bengal, approximately 850 km east-southeast of the Trincomalee coast. It is expected to move northwestwards, away from Sri Lanka and intensify further by 15–16 November, potentially influencing heavy rainfall over Sri Lanka.

Monitoring

Rainfall:During 4-10 Nov, Very heavy rainfall occurred in the western, central and northwestern regions. Highest average rainfall was in Western Hills – 15.6 mm and Eastern Plains – 15.3 mm. Wind:From 2-8 Nov 2026, winds at an elevation of 1.5 km were from the northeast and adjacent regions, with speeds of 3–4 m/s. Temperature: Overall, temperature was typical for November across SL, with Eastern Hills being relatively cooler (26.6°C). Southern Plains recorded the highest average maximum temperature (31.7°C). Eastern Hills recorded the lowest average minimum temperature (18.6°C).

Predictions

Rainfall:NOAA predicts very heavy rainfall (exceeding 135 mm) across Sri Lanka during 10–16 November. Above 135 mm is predicted for the western, southern, northern, central & eastern regions. During Nov-Jan, there is a 50% likelihood of SL receiving higher-than-normal tercile rainfall.Wind:From 11–17 Nov 2026, winds are predicted to speed up to 4–8 m/s, arriving from the northwest. The predictions show a shift in wind direction this week, from easterly to northerly.

Indian Ocean (IO) SST

According to CCSR/IRI climate forecasts, there is a 75-95% probability of a positive IOD from November through December 2026. The Dipole Mode Index (DMI) has increased to +0.75°C from +0.69°C last week.

El Niño Event

 El Niño prevailed across the equatorial Pacific Ocean with the Niño 3.4 averaging 3.3°C above average – this remains one of the strongest El Nino events.

Rainfall Prediction

From 10–16 Nov, very heavy rainfall exceeding 135 mm is predicted across Sri Lanka. Rainfall exceeding 135 mm is predicted for the Western Hills and Plains, Eastern Hills and Plains, and Southern and Northern Plains. From 17–23 Nov, rainfall exceeding 135 mm is predicted for the Western Hills and Plains and Eastern Hills and Plains. 

(Source: NOAA CPC)

Monitored Rainfall

The average daily rainfall across Sri Lanka was 13.8 mm during 4–10 Nov. The highest regional averages were recorded in the Western Hills (15.6 mm) and Eastern Plains (15.3 mm). Very heavy rainfall occurred in the Western, Central and North-Western regions, with Colombo recording 123 mm on 6 Nov and Pottuvil recording 93 mm on 10 Nov.

Monitored Land & Sea Temperature

Overall, temperatures were typical for November across Sri Lanka, with the Eastern Hills being relatively cooler (26.6°C). During 4–10 Nov, the average maximum temperature across Sri Lanka was 30.7°C, lower than the previous week’s average of 31.0°C. Sea surface temperatures around Sri Lanka were 1.5–2.0°C warmer than the seasonal average along the Western coasts and 1.0–1.5°C warmer along the remaining coasts.

Monitored & Predicted Wind

Winds during the last week were predominantly from the Northeast and adjacent regions, with low speeds. Predictions for the coming week indicate a shift in wind direction from easterly to northwesterly winds. From 2–8 Nov 2026, winds at an elevation of 1.5 km were from the Northeast and adjacent regions, with speeds of 3–4 m/s. From 11–17 Nov 2026, winds are predicted to speed up to 4–8 m/s, arriving from the Northwest.