Le Thanh Hai, deputy director of the National Centre for Hydro-Meteorological Forecasting, talked to Viet Nam News about the strange weather conditions the country has been experiencing.
Continuous hailstorms have wreaked havoc on at least eight northern mountainous provinces since last week, causing one death, 43 injuries and huge damages to property. In addition, the drought, which is believed to be the most severe in the last decade, has devastated the central region for several months. Do you think that these are unusual weather phenomena?
Firstly, we should clearly distinguish the two types of weather phenomena. Drought in the central region belongs to the category of ‘extreme' weather while whirlwinds and hailstorms should be classified as ‘severe' weather.
Extreme weather phenomena are rare and irregular occurrences. They happen about once every couple of years, and they usually come in the form of droughts, floods and powerful storms.
The drought in the central region is linked to the previous rainy season that finished in late October 2012, much earlier than the usual December. Rainfall only reached half the expected amount and the region saw only a few storms of note last year, except for Gaemi in October.
As a result, water levels in hydro-electric power plants, reservoirs and groundwater have been seriously reduced. The drought is forecast to last until the end of July in the central region, with rains expected to arrive at the beginning of August.
The increasing number of extreme weather cases is thought to be one of the effects of climate change, while severe weather is now occurring on a cyclical basis in many regions around Viet Nam. bringing hailstorms and thunderstorms.
Severe thunderstorms are most common in the northern mountainous provinces of Lao Cai and Ha Giang during spring – end of March to May.
I think the hailstorms that hit northern mountainous provinces in late March are not unusual. However, the magnitude of these hailstorms might be the biggest yet. We recently measured hail stones with an unprecedented diameter of 10-14 centimetres. Hail stones normally are no bigger than 3-5 centimetres, the same size as an average big toe.
We may see even more severe thunderstorms continuing to occur in northern mountainous provinces until May.
How can we improve our forecasting capacity to help people take immediate precautions?
Extreme weather is foreseeable. By November of last year, we had already forecast the drought that is now hitting the central region.
However, it is difficult to give detailed forecasts to communes and wards about severe thunderstorms. The lack of facilities and human resources are one of difficulties we meet, so we are only able to give warning about heavy rains and thunderstorms in big areas such as the whole region of the north, central or the south.
Severe thunderstorms are a weather phenomenon happening on a small scale- small in terms of both space and time- making them hard to predict.
We can forecast in detail about how and when a storm or tropical pressure system will hit because storm and tropical pressure systems reach out hundreds of kilometres and over five or seven days.
Meanwhile, severe thunderstorms, including hailstorms, only spread out over dozens of kilometres and last for just a few minutes. So warnings can only come 1-2 hours beforehand.
Tornadoes are one such example. In America. a tornado's warning time is only 5-10 minutes before it occurs and it covers just hundreds of metres and lasts only for a few minutes.
Recently, big cities such as Da Nang, Ha Noi, Hai Phong and HCM have piloted warning systems that can give a short-term alert for heavy rains and thunderstorms. However, such warnings cannot yet be reproduced in other provinces due to the shortage of human resources and facilities.
In the long term, Viet Nam will draft a plan to operate a digital weather forecast system with observation stations, weather radar and advanced technologies to upgrade on their current weather forecasting activities. Such plans however will require a big investment in time and will need a strong strategic plan.
What advice would you give for people living in regions vulnerable to extreme weather and severe thunderstorms?
The people living in the mountainous provinces near Hoang Lien Son Mountain particularly should observe weather changes to detect severe thunderstorms early.
Severe thunderstorms occur when black clouds cover the sky during the day time, which can continue longer into the night if there is a sudden drop in temperature.
Following weather forecasts on the radio and television is also highly recommended. — VNS