Typhoon Sansan Approaches: Heavy Rain and Flood Warnings for Kinki and Tokai Regions

2024/08/31 09:51 Weather News

As of 9:00 AM on August 31 (Saturday), Typhoon No. 10 (Shanshan) is moving southeast over the sea southwest of Tanabe City, Wakayama Prefecture. Although the area of strong winds has decreased, active rain clouds are spreading to the northeast and east of the center, necessitating caution for heavy rain, particularly in the Kinki and Tokai regions.

▼ Typhoon No. 10 As of 9:00 AM on August 31 (Saturday)
　Location　　　About 50 km southwest of Tanabe City
　Size classification　　／／
　Strength classification　　　／／
　Movement　　　　　Southeast at 15 km/h
　Central pressure　　　996 hPa
　Maximum wind speed　　　18 m/s
　Maximum gust speed　　25 m/s
» Latest typhoon information

Active rain clouds in Kinki, Tokai, and Hokuriku

With the eastward movement of the typhoon, the rain in China and Shikoku has peaked, and active rain clouds have spread to Kinki, Tokai, and Hokuriku.

In the vicinity of the upper air pressure trough and shear line (the boundary where the wind flow changes), rain cloud development is prominent, with very heavy rain of 39.5 mm observed in Ogaki City, Gifu Prefecture, and 30.0 mm in Takayama, Wakayama Prefecture, in the hour leading up to 9:00 AM. In Fukui City, Fukui Prefecture, 29.0 mm of strong rain was recorded.

In the Kanto region, where heavy rain fell early in the morning, active rain clouds have moved east and the situation is now stable.

In the future, as the typhoon (tropical depression) slows down, it will be easier for active rain clouds to linger in the same areas, leading to the possibility of persistent heavy rain.
» Rain cloud radar

Increased rainfall expected in Tokai

In Kinki and Tokai, it is expected that the situation conducive to increasing rain will continue at least until tomorrow, September 1 (Sunday).

In particular, rainfall is expected to increase in the Tokai region, which is easily impacted by moist air flowing in from the southeast, with places expecting more than 300 mm of rain over the 48 hours until the morning of the 2nd (Monday), and widespread areas expecting more than 200 mm of rain.

Since before the typhoon’s formation, significant rainfall has been recorded mainly in Mie and Shizuoka Prefectures, with a total rainfall of 614.5 mm in Odaicho, Miyagawa, Mie Prefecture, and 590.5 mm in Shizuoka City, since the 27th (Tuesday).

Due to the rain that has fallen so far, the ground has become loose, and river water levels are high, creating conditions prone to disasters. There is a risk of landslides and river flooding due to future rains, so please continue to avoid dangerous areas such as near rivers that are swollen and slopes with loose ground.

High risk of landslides in Kanto and Shizuoka

Rain in Kanto and Shizuoka Prefectures has calmed down a bit, but in some areas, active rain clouds remain. In Odawara City, Kanagawa Prefecture, 5.5 mm of rain was recorded in one hour until 7:00 PM, and at Shizuoka Airport, 32.0 mm.

The risk of landslides has increased in Kanagawa Prefecture extending through Tokyo, Saitama Prefecture, and Shizuoka Prefecture, with particularly widespread areas classified as “danger” level in western Kanagawa and eastern Shizuoka. While the intensity of rain has peaked, moist air continues to flow in, making it easier for rain to occur.

Disasters may occur after the peak of rain, so please check evacuation instructions from local governments and continue to stay in safe places.
» River water levels / live cameras

Heavy rain even in Hokkaido and Tohoku, far from the typhoon

Additionally, northern Hokkaido and Tohoku are experiencing rain cloud development due to the influx of very moist air around the typhoon and a pressure trough moving in from the west. In the hour leading up to 9:00 AM, extremely heavy rain of 63.5 mm was observed in Hiratoku Town, Hidaka region, and 51.5 mm in Hidaka Town.

As of 9:20 AM, heavy rain and flood warnings are in effect for the Kamikawa region, Hidaka region, Tokachi region, and Aomori Prefecture in Hokkaido.

While the heavy rain is relatively short-lived, it is of a magnitude not typical for Hokkaido, so caution is needed for road flooding, rising rivers, flooding, and inundation of low-lying areas.
» Rain cloud radar

Photo: Weather Report (submitted via Weather News app)

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

The thin lines in this figure represent the results of numerical simulations computed by meteorological agencies worldwide. These are the results of calculations of the low-pressure center using an ensemble forecasting method, which incorporates deliberate errors in initial values to evaluate the reliability of the forecasts.

In comparing these, there is a general tendency for the track to turn westward toward western Japan, although the landing region is considered to be anywhere from Kyushu to the Kii Peninsula. There are various possibilities for the track after landing, ranging from those that exit to the Japan Sea to those that travel along the Pacific coast. Even slight differences in tracks can have significant impacts on regions and large differences in the degree of impact, so close attention should be paid to changes in future forecasts. As time progresses, it is expected that errors will be reduced, so please check for the latest information.

Sixth typhoon to occur this month

The occurrence of this typhoon marks the third day since Typhoon No. 9 formed on Monday, the 19th. This is the sixth typhoon formation this month.

Looking at the average number of typhoons occurring, August has an average of 5.7, making it the month with the most frequent typhoon occurrences during the year. This year, six typhoons have already formed, suggesting a pace that is around or above the average.

As we transition from summer to autumn, an increase in typhoons approaching the main island of Honshu is expected, marking the full-fledged typhoon season, so please prepare measures for typhoons and heavy rains.
» Radar Satellite Cloud Image Mode

Name of the Typhoon

The names of typhoons are predetermined, with 140 names prepared in advance proposed by the member countries of the international agency “Typhoon Committee” and assigned in the order of occurrence.

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

Reference Materials