The next day, the storm crossed the southern Japanese islands and entered the Sea of Japan.

Typhoon Pat originated from an active monsoon trough located east of the Philippines in the last two weeks of August.

Forming around the time as Typhoon Odessa and Tropical Storm Ruby, an area of enhanced convection was first noted towards the end of August.

[2][nb 1] Later on August 26, a Hurricane Hunter aircraft reported winds of 70 km/h (45 mph) and a pressure of 999 mbar (29.5 inHg), but did not locate a surface circulation.

Following additional Hurricane Hunter reports, which noted evidence of a surface circulation, the JTWC declared the system Tropical Storm Pat.

[1] Initially poorly organized, Pat headed east-northeast, south of a subtropical ridge.

[2] Meanwhile, the JTWC anticipated the storm to move east-northeast and separate from the monsoon trough before turning west-northwest under a weakening ridge.

[2] By midday on August 29, some tropical cyclone forecast models began to show Pat emerging into the Sea of Japan west of the ridge.

[1] That same day, the JTWC increased the intensity to 160 km/h (99 mph), equivalent to a Category 2 cyclone on the United States-based Saffir-Simpson Hurricane Wind Scale.

During the evening of August 30, the JMA reported that Pat reached its peak intensity of 135 km/h (85 mph) and a pressure of 955 mbar (28.2 inHg).

As Odessa moved east-northeast, Pat accelerated towards the north, and then emerged into the Sea of Japan later on August 31.

In the nearby Yamagata prefecture, a signboard at a school ground fell due to strong winds, injuring four students.

[19] Offshore, ten fishing boats sunk,[11] including one Japanese cargo ship.

Ninety-five other boats took refuge in North Korea,[20] though 59 left on September 2 to return to Japan.