JOHANNESBURG – Cyclone Freddy, which has already hit several countries in south-eastern Africa and caused 21 deaths as at Thursday, is on track to be declared the longest-lasting tropical cyclone on record – beating the previous record of 31 days – as it continues its path of ruin across the region.

After traversing the Indian Ocean, the cyclone bounced between the island nation of Madagascar, where it left 11 people dead, and Mozambique, on the African mainland, where 10 were killed.

It has already boomeranged back to hit Madagascar a second time, and is now expected to return to Mozambique by Saturday.

The cyclone is unusual not only because of its longevity and route but also because it has undergone six separate rounds of rapid intensification.

By Thursday morning, Freddy had been downgraded to a severe tropical storm, but forecasters said that they expect it to power up again, becoming a cyclone once more by the time it returns to thump into the Mozambican coastline.

Freddy is “a once-in-a-lifetime storm”, said Mr Wayne Venter, a forecaster at the South African Weather Service.

The storm appeared more than a month ago and was named on Feb 6 as it took shape near the northern coast of Australia. It then began a journey of more than 6,400km across the Indian Ocean.

Meteorologists have not seen that path in two decades, and only three other storms have been recorded travelling from the east to the west of the Indian Ocean, according to a tracking agency at the US National Oceanic and Atmospheric Administration.

Freddy crossed over the islands of Mauritius and Reunion, a territory of France, bringing heavy rain and some flooding, but turned deadly when making landfall in Madagascar on Feb 21, despite its intensity having dropped.

The cyclone picked up power again in the warm channel of water between Madagascar and mainland Africa before reaching Mozambique on Feb 24, where flooding brought more deaths.

The deluge of rain has stretched as far as landlocked Zimbabwe.

Most intense storms peter out after making landfall, but Freddy’s unusual path took the cyclone back out to sea after hitting Mozambique to begin its ricocheting between the African mainland and Madagascar.

During its meandering path, Freddy’s highest sustained wind speeds reached about 257kmh, the equivalent of a Category 5 hurricane, as such storms are known when they form in the Atlantic.

The United Nation’s World Meteorological Organisation, which said Freddy is on track to become the longest-lasting tropical cyclone on record, has set up a committee to evaluate whether it has surpassed the previous mark, set by a tropical cyclone called John in the Pacific in 1994, taking into account Freddy’s shifts in intensity.

Climate change is making furious tempests like Freddy more common, scientists have found.

Just over a year ago, the same area was hit by cyclones Batsirai and Emnati, killing at least 120 people in Madagascar, as the two storms arrived in quick succession.

Mozambique was bracing itself on Thursday for Freddy’s return. As well as the 10 deaths in the country, around 9,900 people have been displaced from their homes, according to the UN Office for the Coordination of Humanitarian Affairs.

Villages in Mozambique were cut off by fallen trees or burst river banks as the storm unleashed its fury, with estimates of around 28,300 houses destroyed.

In the worst-affected areas, such as the port city of Beira, people waded through waist-high water to reach drier ground or help rescue efforts.

The authorities in Mozambique say they fear that 1.75 million people could be affected by the cyclone when it returns, and aid agencies have urged people to remain in shelters for a few more days.

The indirect impact of Freddy has been felt across southern Africa, where summer rains have dried up as the cyclone sucks moisture from the Indian Ocean, said Mr Venter, the forecaster.

The trail of devastation also brings a heightened risk of disease. Mozambique is already battling a cholera outbreak, with more than 7,500 cases reported. Floodwaters could destroy clinics and help spread the illness, the World Health Organisation in Africa warned. NYTIMES