The South-West monsoon has set in over Sri Lanka, the island nation’s meteorological department announced this (Wednesday) morning, at least six days behind schedule. Sri Lanka is the penultimate stop before the monsoon entourage reaches the Kerala coast in mainland India.
Barring exceptional circumstances, the seasonal system typically takes up to a week to advance from Lanka to Kerala. As of Wednesday noon, supportive but weak south-westerlies were gradually establishing themselves along the Kerala coast, though upper-level winds remained resistant to a favourable shift in direction.
Likely Kerala onset
Conditions are expected to turn more conducive around June 2–3, when stronger monsoon-friendly south-westerly to westerly winds are forecast to strengthen toward the coast. The monsoon could, thereafter, make an onset over Kerala at any time, depending on how quickly upper-atmospheric winds fall into alignment.
In the wake of the monsoon’s arrival, the Sri Lankan met agency has forecast showers or thundershowers at times over the Western, Sabaragamuwa and North-Western provinces, and across the districts of Galle, Matara, Kandy and Nuwara Eliya. Fairly heavy rainfall exceeding 7.5 cm is likely at isolated locations.
Fairly strong winds
It has also warned of fairly strong winds of 30–40 km/hr at times over the western slopes of the central hills, and across the Northern, North-Central, North-Western and Southern provinces, besides Trincomalee district. Onset phases here in ideal conditions typically witness low-level winds at higher speeds across the region.
Back home, numerical model guidance from the India Meteorological Department (IMD) suggests low-level winds may remain unfavourable for the monsoon onset until at least June 3. Conditions appear to improve during June 4–5, when south-westerlies strengthen decisively over the Kerala coast, though the alignment may weaken soon thereafter. Upper-level winds are projected to be the culprits, offering little onward support.
Onset conditions
The European Centre for Medium-Range Weather Forecasts (ECMWF) broadly concurs with the June 4-5 timeline for Kerala. For the IMD to formally declare monsoon onset here, westerly winds must not only intensify at lower levels, but also persist and deepen vertically up to around 4.5 km in the atmosphere. Current projections by ECMWF suggest this vital combination may not fully materialise until June 4–5.
Published on May 27, 2026