Tropical Storm Mirinae approaches mainland Japan, could impact Olympics

Officials and athletes at the Olympics continue to battle sweltering conditions as heat and humidity prevail in the Tokyo, but once again, a tropical system brewing nearby could offer some relief but could also be disruptive to the final days of the Games.

As competitions continue in the Japanese capital, AccuWeather forecasters have been monitoring the northern Philippine Sea for tropical development since late last week. Earlier this week a tropical depression began to take shape near the Ryukyu Islands of southern Japan.

By Thursday, local time, the depression strengthened into a tropical storm near Okinawa and was given the name Mirinae by the Japan Meteorological Agency.

As an area of high pressure over the Pacific Ocean builds west into the Philippine Sea this week, a nontropical storm system will swing by to the north of Japan. Both of these features will help to steer Mirinae along the southern coast of Japan.

However, the exact movement of the high and the nontropical storm will play a role in precisely where the tropical storm tracks. Mirinae is expected to track near the southern coast of Japan, but a slight change in position of the other two features could change the trajectory.

As Mirinae follows this generally northeastern path it will struggle to gain additional intensity since the storm will be battling moderate wind shear over the region. Sea surfaces temperatures off the southern coast of Japan are also seasonably cool. Tropical activity in recent weeks, including Nepartak, has helped to agitate the waters, bringing cooler water to the surface.

Regardless, AccuWeather forecasters warn that Tropical Storm Mirinae can still bring some impacts to portions of southern Japan as it tracks near or briefly over the coast areas of the Kanton region.

"Some rain may reach Tokyo as early as Friday night, but the heaviest rain is expected later Saturday into early Sunday," said AccuWeather senior meteorologist Tony Zartman. "Rain, some heavy, and gusty wind can impact Tokyo and cause delays for outdoor events at the Olympics this weekend."

Medaling events for baseball, softball, beach volleyball, canoe sprint, soccer and golf are all scheduled to take place on Saturday or Sunday.

Rainfall from Mirinae is forecast to taper off by Sunday afternoon, allowing dry conditions to return to Tokyo before the closing ceremonies begin at 8 p.m.

One thing working in Tokyo's favor is the wind shear across the region and the effect it has of the distribution of rainfall surrounding the center of Mirinae.

"As of Thursday night, local time, most of the rain is getting sheared off to the right," said Zartman. This would mean even if storm tracks close to the Kanto region, the heaviest rain could remain on the right side of the storm and out over the ocean.

In addition, if the storm track shifts farther south and away from mainland Japan, Mirinae would deliver less rain and wind to Tokyo.

As Mirinae continues tracking to the northeast early next week and transitions into a nontropical system, some tropical moisture lingering near Japan can fuel showers and thunderstorms as athletes begin trips home and cleanup efforts commence in Tokyo.

This may not be the last tropical threat for Japan. Lupit, currently a tropical storm swirling over the southeastern coast of China, is forecast to bring heavy rain to eastern China and Taiwan before forging a track toward Japan and the Korean Peninsula next week.