Another Olympic disruption? Brewing tropical system could target Japan

 By Maura Kelly, AccuWeather meteorologist

Updated Aug. 1, 2021 12:37 AM EDT

As Olympic officials try to handle the ongoing struggle with the heat in Tokyo, they will have to turn their attention to another potential trouble: a brewing tropical system.

The storm could bring impacts to the Olympic Games early this week -- and AccuWeather meteorologists warn this may not be the last tropical concern for the host country.

The tropical low is currently located to the southeast of mainland Japan in the northern Philippine Sea. While the low had a chance to develop into an organized tropical system, the window for that opportunity is quickly closing it moves into a harsher environment.

The storm is moving into an area of moderate wind shear and lower sea surface temperatures. Waters to the south and east of Japan were stirred up after Nepartak followed a similar track last weekend, which caused cooler water to come to the surface.

AccuWeather Meteorologist Rob Richards expects this storm to begin losing intensity rather quickly as it approaches northern Japan by Sunday, but it can still bring some impacts to the region.

"This low will move into northern Japan, bringing enhanced rain and gusty winds on Sunday, local time," explained Richards, adding that the most likely areas to be impacted by the storm are from the city of Sendai on north.

These areas, which include portions of the Tohoku and Hokkaido regions, can receive up to 1.00-1.50 inches (25-40 mm) of rainfall with locally higher amounts possible in the mountains. Wind gusts can also reach as high as 30-40 mph (50-60 km/h), especially near the center of the area of low pressure.

Kolohe Andino, of the United States, rides a wave during the first round of the men's surfing competition at the 2020 Summer Olympics, Sunday, July 25, 2021, at Tsurigasaki beach in Ichinomiya, Japan. (Olivier Morin/Pool Photo via AP)

This rain can lead to localized flooding in low-lying areas as well as in areas that received heavy rainfall from Nepartak last weekend.

While the last of the track and field and marathon events occurring in Sapporo took place on Friday, local time, any traveling between this northern location and Tokyo could be impacted by locally heavy rainfall.

Due to the forecast track of this low, major impacts are not expected across the Kanto region, including in Tokyo.

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This may not be the last chance for Tokyo to receive some enhanced rainfall. A plume of tropical moisture following behind the area of low pressure can move over Kanto on Monday and bring a couple of showers and thunderstorms to the region.

Paula Badosa, of Spain, is helped off the court in a wheelchair after retiring due to illness during the quarterfinals of the tennis competition at the 2020 Summer Olympics, Wednesday, July 28, 2021, in Tokyo, Japan. (AP Photo/Seth Wenig)

Any rainfall this weekend is unlikely to cause major delays, said Richards, but any showers could bring some short-lived relief from the heat plaguing Tokyo.

Regardless of the track of this tropical feature, it can bring increased wave heights and rough seas to the southern and eastern coasts of Honshu into early this week. This could pose some risk to the sailing events taking place in Sagami Bay.

Following in the wake of this tropical low, a second tropical low will begin to take shape over the same region of the Philippine Sea by early this week.

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"The next one could be one to watch since that has more potential to become a tropical depression or tropical storm," said Richards, adding that there is still plenty of uncertainty regarding how strong it can become and where it will track.

An area of high pressure is forecast to build over Japan this week, this could steer the brewing tropical system to the west before it has much chance to track northward, but it is still too early to completely rule out impacts to southern Japan this week.

According to Richards, it is not unusual for multiple systems to develop and then track over a similar area in the West Pacific tropical basin. "Sometimes a pattern can develop where back-to-back lows affect Japan or other areas of the basin."

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