Highlights

Cyclone Arnab

Cyclone Murasu began developing as a low-pressure area over the Central Bay of Bengal on 29 October, approximately 1200 km northeast of the Trincomalee coast, and intensified into a Severe Cyclonic Storm by 2 November and made landfall in Southern Andhra Pradesh, on 3 November. Its winds led to increased rainfall over the mountain slopes and southwestern regions of Sri Lanka.

Monitoring

Rainfall: During 26 Oct – 1 Nov, there was very heavy rainfall in western and northwestern regions. Highest average rainfall was in Southern Plains – 21.8 mm and Eastern Hills – 16.7 mm. Wind: From 25-31 Oct 2026, winds at 1.5 km elevation were from the South-West and adjacent regions at  speeds of 6-10 m/s. Temperature: Overall, temperature was typical for October across SL, with Eastern Hills being relatively cooler (26.9°C). Eastern Plains recorded the highest average maximum temperature (32.6°C). Eastern Hills recorded the lowest average minimum temperature (18.3°C).

Predictions

Rainfall: NOAA predicts very heavy rainfall (75–135 mm) across Sri Lanka during 3–9 November. Above 135 mm is predicted for the western & eastern regions and less rainfall is predicted for northern and southern regions. During Nov-Jan, there is a 50% likelihood of SL receiving higher-than-normal tercile rainfall. Wind: From 4-10 Nov 2026, winds are predicted to slow down to 1-5 m/s, arriving from the North-East. The predictions show a shift in zonal (east-west) wind direction this week, from westerly to easterly.

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 decreased to +0.69°C.

El Niño Event

El Niñ 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 3–9 Nov, very heavy rainfall of 75–135 mm is predicted across Sri Lanka. Rainfall exceeding 135 mm is predicted for the Western Hills and Plains and Eastern Hills and Plains, while 75–135 mm is predicted for the Southern and Western Plains. From 10–19 Nov, rainfall exceeding 135 mm is predicted for the Western Hills and Plains, Eastern Hills and Plains, and Northern Plains.

(Source: NOAA CPC)

Monitored Rainfall

The average daily rainfall across Sri Lanka was 9.9 mm during 28 Oct–3 Nov. The highest regional averages were recorded in the Southern Plains (21.8 mm) and Eastern Hills (16.7 mm). Very heavy rainfall occurred in the Western and North-Western regions, with Ratmalana recording 78 mm on 31 Oct.

Monitored Land & Sea Temperature

Overall, temperatures were typical for October across Sri Lanka, with the Eastern Hills being relatively cooler (26.9°C). During 28 Oct–3 Nov, the average maximum temperature across Sri Lanka was 31.0°C, higher than the previous week’s average of 30.2°C. Sea surface temperatures around Sri Lanka were 1.0–2.0°C warmer than the seasonal average along the Western coasts and 0.5–1.0°C warmer along the remaining coasts.

Monitored & Predicted Wind

Winds during the last week were predominantly from the Southwest and adjacent regions, with high speeds. Predictions for the coming week indicate a shift in wind direction from the Westerly to the Easterly regions. From 25–31 Oct 2026, winds at an elevation of 1.5 km were from the Southwest and adjacent regions, with speeds of 6–10 m/s. From 4–10 Nov 2026, winds are predicted to slow down to 1–5 m/s, arriving from the Northeast and adjacent regions.