A resident is heard saying, “A tornado is happening,” during the large-scale fire in Oita’s Saganoseki district on Nov. 18. (Provided by a resident)

Photo/Illutration An expert said a fire whirl likely occurred in the blaze that has engulfed parts of Oita’s Saganoseki district. (Provided by a resident)

OITA—A “fire whirl” was observed in the deadly conflagration that has devastated the Saganoseki district of Oita city.

Kazunori Kuwana, a Tokyo University of Science professor well-versed in the phenomenon, also called a “fire tornado,” observed flames and smoke rising in a swirling motion and moving horizontally in video footage taken by a resident.

“Both are characteristics of a fire whirl, and it is reasonable to conclude that one occurred,” Kuwana said. “Its height may have been several tens of meters.”

According to Kuwana, fire whirls are more likely to form during large-scale fires when certain conditions related to wind turbulence, terrain and positional relationship between roads and buildings coincide.

The Saganoseki district’s complex terrain surrounded by mountains may have contributed to swirling winds that allowed for the formation of a fire tornado, he said.

When a fire whirl occurs, the updraft strengthens, increasing the force that can scatter embers and lead to spot fires.

However, fire swirls can also occur in blazes involving only a few houses, and their occurrence does not necessarily result in large-scale damage, he said.

Kuwana said although it cannot be definitively said that the fire whirl expanded damage in the Saganoseki district, “it represents one phenomenon that symbolizes the complexity of the spread mechanism in large-scale fires.”

Firefighters continue to battle the fire that broke out on the evening of Nov. 18.

So far, it has burned about 170 buildings over an area of about 4.89 hectares.

The body of a 76-year-old fisherman was found in the charred remains of a house.

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