Heavy-rain threshold jumps back above 100 mm for Thursday as monsoon strengthens

The Department of Meteorology has warned that showers exceeding 100 mm are likely at some places on Thursday (6) as the southwest monsoon intensifies over the island.

Rainy and windy conditions affecting the southwestern parts of the country are expected to increase from Thursday and continue over the following days, the department said.

Falls above 100 mm are forecast in parts of the Western and Sabaragamuwa provinces and in the Kandy, Nuwara Eliya and Galle districts. Showers or thundershowers will occur intermittently in the Western, Sabaragamuwa and North-Western provinces and in the Kandy, Nuwara Eliya, Galle and Matara districts.

Showers or thundershowers may also occur in parts of the Ampara, Batticaloa and Monaragala districts after 2.00 p.m. Strong winds of around 40 to 50 km/h are expected at times over the North-Central, Sabaragamuwa, Southern, Central and North-Western provinces.

The department urged the public to take precautions against damage from temporary strong winds and lightning during thundershowers.

The recovery has reversed

Thursday’s bulletin ends a week of easing. The threshold stood at 50 mm on Sunday, doubled to 100 mm on Monday, stepped down to 75 mm on Tuesday and held flat at 75 mm on Wednesday. It now returns to its highest level of the spell.

The heavy-rain zone has also widened. Wednesday’s forecast confined falls above 75 mm to Sabaragamuwa and the Kandy and Nuwara Eliya districts; Thursday’s adds the whole Western province and the Galle district.

Forecast a week in advance

The turn is the one the department itself signalled. Met Director General Ajith Wijemanna said on Monday that the wet spell would weaken around midday on Tuesday, but warned that a developing Pacific typhoon could enhance the southwest monsoon and push rain back onto the country after August 6.

That mechanism was flagged earlier still. The department’s June seasonal outlook cautioned that a dry July-to-September projection could be overturned if Pacific typhoons developed and strengthened the monsoon flow.

Sources: Ada Derana.