Cyclone Ditwah caused landslides in the central mountainous tea-growing regions of Badulla and Nuwara Eliya.

Floods and landslides in Sri Lanka have killed at least 56 people as Cyclone Ditwah, a deadly tropical storm, swept across the South Asian country on Friday.

Here is what we know.

What has happened?

Cyclone Ditwah made landfall early on Friday morning, affecting mainly the eastern and central regions of the island nation, with wind speeds of 65 kilometres per hour (40 miles per hour).

Before and after a tropical cyclone or storm makes landfall, it causes heavy rain. Sri Lanka saw a downpour of heavy torrential rainfall exceeding 300mm (11.8in) between Thursday and Friday.

The rain triggered flooding and landslides, in which many people have been killed.

What do we know about casualties?

The death toll across Sri Lanka rose to 56 on Friday.

On Thursday, more than 25 people were reported killed in landslides in the central mountainous, tea-growing regions of Badulla and Nuwara Eliya, which is about 300km (186 miles) east of the capital, Colombo. Others lost their lives in landslides in other parts of Sri Lanka.

A further 21 people are missing and 14 have been injured in the Badulla and Nuwara Eliya areas, according to the government’s disaster management centre. In all, 23 people are missing across the country.

What damage and disruption has there been?

The heavy downpour has destroyed four houses and damaged more than 600.

It has also caused trees and mud to fall and block multiple roads and railway lines.

The weather conditions have caused flight disruptions.

Fifteen flights, including services from Muscat, Dubai, New Delhi and Bangkok, were diverted from Bandaranaike International Airport (BIA) in Colombo to Mattala Rajapaksa International Airport (MRIA) in Sri Lanka’s southern province, Mattala, as well as to Trivandrum and Kochi in India from Thursday and through to Friday afternoon, local media reported.

How have the authorities responded?

The country’s Disaster Management Centre (DMC) evacuated 43,991 people from 12,313 families to schools and other public shelters, local media reported on Friday morning.

The media also showed footage of military helicopters rescuing three people stranded on the rooftop of their home on Thursday in Hanwella, a town in Sri Lanka’s Colombo District. The navy and police also evacuated people by boat.

The government announced the closure of all government offices and schools on Friday.

Additionally, train services were suspended, and the Colombo Stock Exchange announced an early trading finish.

The authorities closed several roads across the country after landslides sent rocks, mud and trees onto roads and rail lines, some of which were also submerged by floodwaters.

What causes a storm like this?

Tropical storms develop over warm ocean waters near the equator. Warm air rises, creating a zone of low pressure. As this air cools, it is displaced by more rising warm air from below, setting up a continuous cycle that generates strong winds and heavy rainfall.

As the system intensifies and its rotation speeds up, a calm, clear eye forms at the centre, marked by very low air pressure.

Once wind speeds reach 63km/h (39mph), the system is classified as a cyclonic or tropical storm – Cyclone Ditwah has a wind speed of 65km/h, giving it a current technical designation of storm. If winds increase to 119km/h (74mph) or more, it becomes a tropical cyclone.

What is the latest on the ground?

Schools and government offices remained closed on Friday. Road and train closures also remain in effect.

The Irrigation Department has issued a red-level flood warning for low-lying areas along the Kelani River valley for the next 48 hours, warning that the risk zone includes Colombo, the capital.

What is the economic situation in Sri Lanka now?

Last year, Sri Lanka elected leftist Anura Kumara Dissanayake as its president, who had pledged to end painful austerity measures imposed by his predecessor, Ranil Wickremesinghe, as part of a bailout loan package from the International Monetary Fund (IMF).

While Dissanayake was initially opposed to the IMF deal, the deal remains in place as he attempts to improve the country’s economy instead.

This year, the economy has seen some early signs of improvement, particularly in the tourism sector. However, the recovery is fragile and heavily dependent on debt management.