Over 100mm of Rain in Under an Hour Triggers Flash Floods in Colombo; Met Chief Warns of Intense Downpours and Blocked Drains Worsening Flood Risks

COLOMBO (News 1st): The Department of Meteorology says more than 100 millimetres of rain fell over Colombo in less than an hour last evening.

Director General Ajith Wijemanne said the intense rainfall triggered flash floods in several parts of the city.

He warned that similar spells of intense rainfall could occur at certain locations in the southwestern parts of the country over the next few days.

Wijemanne further explained the cause behind the sudden bursts of heavy rainfall and its impact.

According to the Director General, close to 123 millimetres of rainfall was recorded in Colombo yesterday.

He explained that the intensity of the rainfall, which occurred within a very short period, contributed to flash flooding in the city.

Colombo had previously recorded rainfall levels approaching 140 millimetres per hour, with more than 100 millimetres falling within a short period on such occasions.

Director General Wijemanne also pointed to blocked or obstructed drainage systems as a contributing factor to the flooding.

He explained that Sri Lanka is currently experiencing the Second Inter-Monsoon season, during which convective rainfall is common. Cloud formations typically develop after sunny morning conditions, bringing heavy showers within 30 minutes to an hour, particularly after 1 p.m.

The prevailing El Niño conditions and the presence of the Intertropical Convergence Zone (ITCZ) in the vicinity of Sri Lanka are also contributing to these rainfall patterns.

Changes in wind direction and atmospheric instability in the lower atmosphere are further creating conditions favourable for sudden, intense rainfall.

Wijemanne warned that similar weather conditions could continue over the coming weeks, particularly across the Western, Sabaragamuwa, North Western, Central and Southern Provinces, including the Galle and Matara districts.

Some areas could experience rainfall exceeding 100 millimetres within a very short period.

Meanwhile, heavy rainfall last night left several roads and other areas across Colombo inundated, causing severe traffic congestion.

In response, representatives of the relevant institutions met this morning to discuss measures to address flooding in Colombo.

The meeting is currently underway and is being held under the leadership of Mayor of Colombo Vraie Cally Balthazaar, with representatives from all relevant institutions in attendance.