Two typhoons are expected to approach the Japanese archipelago over the weekend, bringing risks of heavy rain and landslides [1], [2].
The simultaneous movement of Typhoon 7 and Typhoon 8 creates a dangerous weather pattern. When combined with the existing rainy-season front, these systems can produce prolonged, intense precipitation that increases the likelihood of catastrophic soil failure in mountainous regions.
Weather forecaster Aimi Sakaguchi said Typhoon 8 may have already transitioned into an extratropical cyclone. However, she said the system still carries the power to bring heavy rain [1].
Local authorities have already issued a Level 4 landslide-danger warning for Nagasaki [1]. This high-level alert follows a period of instability in Northern Kyushu, where the interaction between the storms and the seasonal front has intensified rainfall.
Typhoon 7 is expected to approach Okinawa with a storm zone starting from the early hours of June 26, 2024 [2]. The system is then projected to make its closest approach to the Kanto region on June 27, 2024 [2].
Typhoon 8 is forecast to approach the Kanto region slightly earlier than Typhoon 7, though both are expected to impact the area around the weekend [2]. The convergence of these two systems poses a significant threat to Honshu, Okinawa, and Northern Kyushu.
In some regions, the severity of the current weather has led to the issuance of storm warnings for the first time in three years [3]. These warnings signal a return to extreme weather conditions that have not been seen in the area for several seasons.
Sakaguchi said, "Even if Typhoon 8 changes into an extratropical cyclone, it has the power to bring heavy rain, so be careful" [1].
“Two typhoons are expected to approach the Japanese archipelago over the weekend.”
The interaction between multiple tropical systems and a stationary rainy-season front creates a 'compounding effect' that can lead to rainfall totals far exceeding those of a single storm. By transitioning to extratropical cyclones, storms like Typhoon 8 may lose their defined eye but often expand their wind and rain fields, increasing the geographic area at risk for flooding and landslides across Japan's varied terrain.
