A rain gauge in Vietnam registered almost 1.8 metres of rain in 24 hours last week, which is close to the current world record for the highest daily rainfall in recorded history.

A combination of the remnants of Severe Tropical Storm Fengshen, moisture-laden easterly winds and orographic lifting over mountains in central Vietnam caused a prolonged period of heavy rain between October 22 and 28.

This lengthy spell of heavy rain resulted in flooding and landslides across parts of central Vietnam, with reports of at least 37 deaths and tens of thousands displaced from their homes.

Colossal rainfall in central Vietnam

The heaviest rain during this event occurred around the cities of Huế and Hội An on the country’s central coast.

A rain gauge in the Bạch Mã National Park, located to the south of Huế, registered 1,739 mm of rain in the 24 hours ending at 7pm on October 27. This was within 100 mm of the world record for the heaviest 24-hour rainfall, which currently stands at 1,825 mm from Foc-Foc, Rèunion Island on January 7, 1966.

For comparison to Australia, the annual average rainfall in Sydney is just over 1,200 mm and even tropical Darwin usually only sees about 1,730 mm of rain each year.

The highest directly observed daily rainfall on record in Australia was 907 mm at Crohamhurst in Queensland on February 3, 1893. However, analysis of an extreme two-day rainfall event in 1979 indicates that around 1,352.5 mm is likely to have fallen at the top of Mount Bellenden Ker in the 24 hours ending at 9am on January 5, 1979.

The rain that inundated central Vietnam last week was significantly heavier than anything ever observed in Australia.

More heavy rain on the horizon

Looking ahead, another typhoon is expected to hit central Vietnam later this week, delivering more heavy rain to areas still recovering from the late-October deluge.

Typhoon Kalmaegi, which is currently located near Palawan in the Philippines, will gain strength as it crosses the South China Sea on Wednesday and Thursday before hitting Vietnam on Thursday night into Friday morning.

At this stage, Kalmaegi is expected to make landfall several hundred kilometres to the south of the Huế region. However, flood-weary areas of central Vietnam are still likely to see periods of heavy rain over the coming week as Typhoon Kalmaegi approaches and crosses the coast.

Image: Forecast accumulated rainfall during the next 7 days.

Heavy rain from the remnants of Typhoon Kalmaegi will also spread across parts of Cambodia, southern Laos and Thailand towards the end of this week.