The Department of Meteorology forecast heavy showers of about 100mm for parts of the island on Sunday, and separately warned the fishing and naval communities that a fresh disturbance may form in the Bay of Bengal by Wednesday and deepen into a low-pressure system by around 13 November.

In its forecast issued at 5.30 a.m. on 8 November, the department said showers or thundershowers would occur at most places of the island after 1.00 p.m., with heavy showers of about 100mm likely at some places in the Western, Sabaragamuwa and Central provinces and in the Galle, Matara and Kurunegala districts, island.lk reported, carrying the forecast text in full.

Misty conditions were expected in the Western, Sabaragamuwa, Central and Uva provinces during the early hours, and showers in the coastal areas of the Northern and Eastern provinces in the morning. The department asked the public to take precautions against temporary localised strong winds and lightning during thundershowers.

A new system may form by Wednesday

Hiru News reported in Sinhala that the Meteorology Department expects turbulent conditions to redevelop in the south-eastern Bay of Bengal and around the Andaman Sea by 11 November. The department said that system has the potential to develop into a low-pressure condition by around 13 November, and told the fishing and naval community to remain alert.

Sunday’s rainfall and flooding

Hiru reported the highest rainfall in the 24 hours ending at 8.30 a.m. on Sunday as 110.8mm at Avissawella.

Overnight rain left roads under water in several areas. Several sections of the Kandy National Hospital were inundated, though Hiru’s correspondent reported the water had since receded and cleaning was under way. The area around the Kandy railway station was also flooded following rain on Saturday afternoon.

The Irrigation Department said water levels in the Nilwala, Gin, Kalu and Kelani rivers and in the Attanagalu Oya and Maha Oya remained high. L.S. Sooriyabandara, the department’s Director of Hydrology and Disaster Management, said spill gates were open at the Deduru Oya, Walawe, Udawalawe and Kala Oya reservoirs.

A second-stage landslide warning remains in effect for the Udadumbara divisional secretariat area in Kandy district and the Walapane and Nildandahinna areas in Nuwara Eliya district — the same notices issued on Saturday. Wasantha Senadheera, a senior scientist at the National Building Research Organisation, said people in hill-country and landslide-prone areas should be especially alert to sudden bursts of rain.

Sunday evening update: High Level Road under water at Puwakpitiya

The afternoon rain the forecast anticipated duly arrived. By 6.24 p.m. on Sunday, the Inguruna area of Puwakpitiya on the High Level Road was under water, Hiru News reported. Its correspondent said vehicle traffic was still moving through the stretch despite the flooding.

Puwakpitiya sits on the Avissawella corridor, the same catchment where the day’s highest rainfall of 110.8mm was recorded.

A later Hiru filing at 8.31 p.m. attributes that 110.8mm figure to the Department of Meteorology as the highest recorded anywhere in the island over the preceding 24 hours, and reports that Sunday afternoon’s rain also put Avissawella–Puwakpitiya town and the area around the Avissawella main bus stand under water. It attributes the continuing wet weather across much of the island to inter-monsoon conditions.

Update, Monday 9 November: the 100mm forecast widens to six provinces

The Meteorology Department has carried the same 100mm threshold into Monday, over a larger area than Sunday’s forecast.

Falls exceeding 100mm are possible at some places on Monday in the Western, Sabaragamuwa, Central, North Western, Northern and North Central provinces, and in the Galle and Matara districts, Hiru News reported on Monday morning.

The comparison with Sunday’s 5.30 a.m. forecast is the useful part. Sunday covered three provinces — Western, Sabaragamuwa and Central — plus the Galle, Matara and Kurunegala districts. Monday adds the North Western, Northern and North Central provinces, extending the heavy-rainfall area well into the north of the island, while Kurunegala is no longer listed separately as a district because the North Western province that contains it is now included in full.

This is a rainfall forecast and not a warning tier: the filing attaches no advisory colour or validity window to the 100mm figure, and none should be inferred from it.

What this desk could not verify

Several outlets reported that an “amber” advisory for severe lightning was issued at 11.00 a.m. on Sunday, valid until 1.00 a.m. on Monday and covering a wider list of provinces than the 100mm rainfall forecast. This desk could not retrieve that advisory from a verified newsroom it was able to fetch, so the amber designation, its validity window and its geographic scope are not asserted here. The 100mm figure above belongs to the Meteorology Department’s 5.30 a.m. routine forecast, which covers a narrower area, and the two should not be read as one product.

Context

Sunday’s forecast follows a minor flood warning for the Nilwala Ganga issued the same morning, and the flash flooding that hit Colombo on Friday, after which the Presidential Secretariat ordered a special task force set up under the Colombo Municipal Council.