After storm Bualoi weakened, northern Vietnam experienced a series of tornadoes. Meteorologists have offered preliminary explanations for their causes and formation mechanisms.

According to Hoang Phuc Lam, Deputy Director of the National Center for Hydro-Meteorological Forecasting, storm Bualoi had a notably stronger and broader circulation on the northern side of its eye compared to the southern side.

This is a common feature of most tropical storms. The northern edge typically borders the subtropical high-pressure zone, creating a larger atmospheric pressure gradient. Additionally, the differences in temperature, pressure, and humidity between the storm’s center and the northern periphery are more pronounced. The interaction between these two air masses increases the likelihood of thunderstorms and often results in stronger winds on the northern side of the storm.

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A car was blown into a lake in Hoang Giang, Thanh Hoa, by a tornado. Photo: CTV

“Storm Bualoi, as it moved into North Central Vietnam, had its northern rim over the Red River Delta. This led to strong thunderstorms across the area. Several intense cells developed on the morning of September 29, bringing tornadoes captured on phone cameras by residents in Ninh Binh, Hung Yen, Hai Phong, and other localities,” said Lam.

Though typically small in scale and short-lived, tornadoes formed under stormy conditions can still cause significant damage - especially to temporary housing, roadside infrastructure, and vegetation.

Coastal plains and transitional areas between lowland and midland terrain are particularly prone to the formation of storm cells and tornadoes due to open terrain, high humidity, and fewer obstructions.

Small tornadoes often escape detection by weather stations

As storm Bualoi entered North Central Vietnam, its northern edge swept over the Red River Delta, triggering severe thunderstorms. Multiple intense storm cells formed, accompanied by tornadoes recorded across northern provinces.

Lam noted that due to their limited size and short duration, most tornadoes are only recorded when witnessed and filmed by local residents. The national observation network only detects tornadoes if they occur directly at stations staffed with on-site observers.

“Tornadoes typically have diameters ranging from a few dozen to 100-200 meters. As a result, radar or satellite systems are almost incapable of identifying their precise location or shape. This poses major challenges in measurement, observation, and forecasting. We can only issue general warnings about the possibility of tornadoes during strong thunderstorms,” Lam added.

He also warned that despite their small size, tornadoes can produce wind speeds comparable to those of full-scale storms or intense gusts during thunderstorms. Therefore, they still pose a serious threat to human lives, property, and the environment - especially along their paths.

How are tornadoes forecasted?

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An electronics store in Dam Ha town, Quang Ninh, was wrecked by a tornado. Photo: CTV

Mai Van Khiem, Director of the National Center for Hydro-Meteorological Forecasting, explained that tornadoes are technically a form of vortex similar to storms, but on a much smaller scale in terms of size, area, and duration.

“For large-scale storm systems, we can use satellite imagery, radar, and forecast models to analyze their structure and predict their movement. However, when it comes to narrow, short-lived phenomena like strong thunderstorms or tornadoes, we are almost entirely reliant on direct human observation,” said Khiem.

He added that meteorological science currently remains limited to issuing general alerts on the potential for extreme events such as tornadoes, waterspouts, or hail when powerful thunderclouds develop in hot, humid, and unstable atmospheric conditions. Yet precise forecasts regarding location, intensity, or path remain out of reach.

The tornado that swept through Ninh Binh early on September 29 left devastating consequences for both people and property. Preliminary statistics show nine fatalities and 18 injuries. Additionally, 11 single-story homes were destroyed, 126 others damaged or lost roofs, and 53 power poles were brought down.

In Thai Thuy commune, Hung Yen province, another tornado claimed two more lives. Local authorities reported that it tore through residential areas, ripping metal roofing from homes and even toppling reinforced steel gates.

Tornadoes were also reported in Hai Phong, Quang Ninh, and other northern localities, causing widespread damage to infrastructure, crops, and personal property.

Bao Anh