Typhoon San San Advances Towards Kinki Region, Heavy Rainfall Expected

2024/08/31 07:04 Weather News

As of 6 AM on August 31 (Saturday), Typhoon No. 10 (Shanshan) is moving southeast near Anan City, Tokushima Prefecture. It is expected to continue moving eastward and will head north along the Kii Peninsula by tomorrow, September 1 (Sunday), before likely transforming into a tropical depression by Monday, September 2.

▼ Typhoon No. 10 As of 6 AM on August 31 (Saturday)
　Center Position　 About 40 km south-southwest of Anan City
　Size Classification　／／
　Strength Classification　／／
　Movement　 Southeast at 10 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

Typhoon No. 10 has weakened its maximum wind speed around the center to 18 m/s, reaching the lower limit of its strength as a typhoon. However, the surrounding areas of the typhoon still contain active rain clouds, resulting in heavy rain across Chugoku, Shikoku, Kinki, and Tokai regions. As of 1:30 AM, 38.0 mm of rain was observed in Asahinishi, Okayama Prefecture over one hour, and 40.5 mm of heavy rain was recorded in Sekigahara, Gifu Prefecture by 3:20 AM.

Active rain clouds on the eastern side of the typhoon are covering the Kii Peninsula, and southeastern winds flowing into the typhoon are expected to cause further development of rain clouds when they hit the Kii mountain range. There is a risk of locally very intense rain exceeding 50 mm in one hour, so caution is needed.

Additionally, even in the Kanto region, a bit far from the typhoon, rain is falling due to moist air coming from the south. At Ebina, Kanagawa Prefecture, 36.5 mm of heavy rain was observed up to 5:20 AM. Although it is not raining as heavily compared to yesterday, due to the high cumulative rainfall, caution against disasters should continue.
» Rain Cloud Radar

Possibility of Heavy Rain Exceeding 500 mm

Typhoon No. 10 is expected to slowly move towards the Kii Peninsula after passing through Shikoku. Although the trajectory towards September 2 (Monday) is still highly uncertain, there is a possibility that it will change into a tropical depression and nearly stagnate around the Tokai area. Therefore, heavy rainfall is forecasted primarily in the Kinki and Tokai regions.

In the coming days, maximum rainfall over 500 mm is expected in the mountain areas of Mie and Nara Prefectures, with over 200 mm of heavy rain also possible in the northern central area of Mie, southern Nara, and southern Wakayama.

In Mie Prefecture, significant rainfall has already been recorded, with 374.5 mm in Tsu City and 444.5 mm in Owase City over 72 hours up to 5:30 AM. The previously fallen rain has loosened the ground, making landslides more likely, and rivers may easily overflow. Please remain cautious of upcoming rain and avoid approaching dangerous areas such as flooded locations, rivers with rising water, and unstable slopes.

High Risk of Landslides in Kanto and Shizuoka

Although rain in the Kanto and Shizuoka regions has subsided somewhat, active rain clouds are still present in some areas. In Odawara City, Kanagawa Prefecture, 5.5 mm of rain was recorded over one hour until 7 PM, and 32.0 mm at Shizuoka Airport.

The risk of landslides has become high from Kanagawa Prefecture through Tokyo, Saitama, and Shizuoka, especially in western Kanagawa and eastern Shizuoka where “danger” levels have spread. Although the heavy rain may have peaked, moist air continues to flow in, making rain still likely.

There is a possibility that landslides may occur after the peak of the rainfall, so please check for evacuation instructions from local governments and continue to stay in safe locations.
» River Water Level & Live Cameras

Risk of Stagnation and Meandering of the Tropical Depression from Shikoku to Kinki

The typhoon is expected to leave Kyushu and move eastward near Shikoku today, August 30 (Friday). It is forecasted to change into a tropical depression by September 1 (Sunday).

Even after changing to a tropical depression, it may not smoothly continue eastward but instead stagnate and meander around Shikoku to Kinki due to weak upper-level winds.

Once converted to a tropical depression, the placement of the center will significantly affect the distribution of rain clouds. If rain clouds remain in the same area for an extended period, localized rainfall may exceed expectations, so attention should be paid to changes in the trajectory.

Reference: Numerical Simulation Results of Paths Calculated by Meteorological Agencies Worldwide

This diagram’s thin lines represent the results of numerical simulations calculated by meteorological agencies from around the world. These are the results of calculations for the center of the low-pressure system using the ensemble forecasting method, which introduces intentional errors into initial values to examine the reliability of forecasts.

Comparing these, while there is a general tendency to turn westward towards Western Japan, the regions expected to be landfall stretch from Kyushu to the Kii Peninsula. There are various paths after making landfall, ranging from going out to the Sea of Japan to moving along the Pacific coast. Even slight differences in trajectory can significantly affect the areas and the degree of impact, so close attention is required for future forecast changes. As time goes on, the margin of error is expected to shrink, so please check for the latest information.

Sixth Typhoon Occurrence This Month

The occurrence of this typhoon is the third in three days since Typhoon No. 9 formed on Monday the 19th of this week. This is the sixth typhoon occurrence since the beginning of this month.

Looking at the average number of typhoons, August sees an average of 5.7 typhoons, making it the period with the most typhoons occurring during the year. With the formation of six typhoons already this year, it seems to be on pace with or exceeding the average.

As summer transitions into autumn, the number of typhoons approaching near Honshu is likely to increase, leading to the full-fledged typhoon season, so be sure to prepare for typhoon and heavy rain measures.
» Radar Satellite Cloud Image Mode

Typhoon Names

The names of typhoons are pre-prepared by the international organization “Typhoon Committee,” which has 140 proposed names from member countries, assigned in the order of their occurrence.

Typhoon No. 10 is named “Shanshan (珊珊),” a name proposed by Hong Kong, which is derived from a girl’s name.
» Radar Typhoon Mode

Reference Materials