Typhoon Shanshan Threatens Heavy Rain and Flooding Across Western Japan

2024/08/30 22:22 Weather News

As of 21:00 on August 30 (Friday), Typhoon No. 10 (Shanshan) is moving eastward near Shikokuchuo City in Ehime Prefecture. It is expected to continue moving eastward and will likely change to a tropical depression near Mie Prefecture on September 1 (Sunday).

▼ Typhoon No. 10 As of August 30 (Friday) 21:00
　Center Location　　Near Shikokuchuo City
　Size Class　　　　／／
　Strength Class　　　／／
　Movement　　　　　East at 20 km/h
　Central Pressure　　996 hPa
　Maximum Wind Speed　18 m/s
　Maximum Gust Speed　25 m/s
» Latest Typhoon Information

Heavy Rain in China, Shikoku, and Kinki Regions

Active rain clouds are accompanying the typhoon, with heavy rain of around 20mm per hour falling mainly in China, Shikoku, and the Kii Peninsula.

Additionally, the active rain clouds on the eastern side of the typhoon are beginning to cover the Kii Peninsula, and the southeastern winds blowing into the typhoon are expected to further develop the rain clouds as they collide with the Kii Mountain Range.

There is a risk of very heavy rain exceeding 50mm per hour locally after tonight.
» Rain Cloud Radar

Heavy Rain Expected to Exceed 500mm in the Next 48 Hours

Typhoon No. 10 is expected to slow down as it moves through Shikoku tomorrow. It may weaken to a tropical depression and nearly stagnate near the Kii Peninsula, which is likely to result in heavy rainfall mainly in the Kinki and Tokai regions.

Over the next 48 hours, over 500mm of rain is expected along the mountain areas of Mie and Nara prefectures, with the potential for over 200mm of heavy rain in central Mie, southern Nara, and southern Wakayama.

In Mie Prefecture, rainfall was aggregated mainly on August 29 (Thursday), with 358.5mm recorded in Tsu City and 410.5mm in Owase City over the 72 hours up to 22:00 today. The rain that has fallen so far has loosened the ground and increased the risk of landslides, and rivers are also at risk of flooding. Please remain vigilant of further rainfall and avoid dangerous areas such as flooded locations, nearby swollen rivers, and unstable slopes.

High Risk of Landslides in Kanto and Shizuoka

While the rain in Kanto and Shizuoka Prefectures has subsided slightly, some areas are still experiencing active rain clouds. In Odawara City, Kanagawa Prefecture, 5.5mm of rain was observed over one hour until 19:00, and 32.0mm was recorded at Shizuoka Airport.

The risk of landslides remains high from Kanagawa to Tokyo, Saitama, and Shizuoka, especially in western Kanagawa and eastern Shizuoka where “danger” level areas are widespread. Although the peak of the strong rain is over, moist air continues to flow in, making rain likely to occur.

Landslides may occur after the peak of the rain has passed, so please confirm evacuation instructions from local authorities and continue to stay in safe areas.
» River Water Levels – Live Camera

Possibility of Stagnation and Meandering from Shikoku to Kinki after Becoming a Tropical Depression

The typhoon is expected to leave Kyushu on the 30th (Friday) and move eastward near Shikoku. It is likely to change into a tropical depression on September 1 (Sunday).

Even after changing into a tropical depression, it may stagnate and meander near Shikoku and Kinki, due to weak upper-level winds.

When the typhoon changes into a tropical depression, the distribution of rain clouds will greatly change depending on the position of the center. If the rain clouds remain over the same area for a long time, there is a possibility of local rainfall exceeding expectations, so care must be taken regarding changes in the path.

Reference: Numerical simulation results of routes calculated by meteorological agencies around the world

Each slender line in this diagram represents the results of numerical simulations calculated by meteorological agencies from various countries. These are the calculations of the low-pressure center using the ensemble forecasting method, which involves intentionally introducing errors into the initial values to evaluate the reliability of the forecasts.

When comparing these, there is a general tendency for the turn towards western Japan, but regions of landfall are considered to be from Kyushu to the vicinity of the Kii Peninsula. Various paths after landfall, such as exiting to the Japan Sea or moving along the Pacific coast, are also possible. Even slight differences in paths can lead to significant differences in affected areas and the degree of impact, so it is necessary to closely observe future forecast changes. The error is expected to decrease over time, so please ensure you check the latest information.

The Sixth Typhoon of This Month

The occurrence of the typhoon is the third day since Typhoon No. 9 formed on Monday, August 19. This is the sixth typhoon to form this month.

Looking at the average number of typhoons forming, August has an average of 5.7 per year, making it the month with the highest occurrence of typhoons. With six typhoons already formed this year, it seems to be on pace with or above the average.

As we transition from summer to autumn, it is likely that more typhoons will approach the vicinity of Honshu, marking the beginning of the full-fledged typhoon season. Please prepare for typhoons and heavy rain.
» Radar Satellite Cloud Image Mode

Typhoon Naming

The names of typhoons are pre-prepared by member countries of the international organization “Typhoon Committee,” with 140 names available, given in order of occurrence.

The name of Typhoon No. 10, “Shanshan,” is a name proposed by Hong Kong, derived from a girl’s name.
» Radar Typhoon Mode

Reference Materials and More