"Monster Torrent" Batters Japan... The Identified Cause That Left Experts "Unbelieving"

[Anchor]

Japan's Meteorological Agency also fell short of expectations in terms of forecasting accuracy. It completely failed to anticipate the record-breaking downpour that left catastrophic damage in Chiba Prefecture last month. The Japan Meteorological Agency explained that the torrential rain at the time was caused by massive cumulonimbus clouds reaching up to 15 kilometers in height, describing it as an unprecedented phenomenon.

Correspondent Mun Junmo has the report.

[Reporter]

On the night of August 13 last year, a sudden downpour struck Chiba Prefecture.

Vehicles were submerged in water, and villages turned into lakes.

Evacuation orders were issued for 400,000 people, and 13 people lost their lives.

Losses from this heavy rain amount to approximately 100 billion won in Korean currency.

A rainfall of 348 mm—three times the average total precipitation for the entire month of August in a typical year—poured down in just 12 hours, creating a "monster downpour" that even the Japan Meteorological Agency failed to foresee.

The Meteorological Research Institute of the Japan Meteorological Agency announced the results of its analysis, stating that massive cumulonimbus clouds reaching a height of 15 km developed starting at 5:30 PM on the 13th and lingered over Chiba Prefecture for more than six hours.

These cumulonimbus clouds were of a "squall line type," which typically move at a fast pace due to the winds they generate, but this time was different.

[Adachi / Head of Laboratory, Meteorological Research Institute, Japan Meteorological Agency: It was hard to believe at first because it is conventional wisdom among researchers that developed squall-line-type cumulonimbus clouds move quickly.]

The agency explained that the winds generated by the cumulonimbus clouds and the opposing winds blowing from the Pacific Ocean were similar in intensity, causing the clouds to stay in one place for a long time.

As the stagnation prolonged, the falling rain created cold air, which pushed up the warm air near the ground, repeating a cycle that caused the cumulonimbus clouds to develop even higher.

[Adachi / Head of Laboratory, Meteorological Research Institute, Japan Meteorological Agency: It was shocking that a phenomenon with insufficient research accumulation actually occurred and led to such a disaster.]

The Meteorological Agency urged caution, noting that even after the rain stops, soil erosion and landslide accidents continue to occur—such as those near Mt. Fuji—as the prolonged rainfall has weakened the ground.

(Video taken by Han Chul-min and Moon Hyun-jin | Video edited by Yoon Tae-ho | Design by Park Tae-young and Kim Ye-ji)
※ Please note: This article was translated by AI and may contain errors.