Usagi (ウサギ, "Rabbit"), which refers to the constellation Lepus in Japanese, was the fourth typhoon and the nineteenth tropical storm in the basin.

Early on September 16, 2013, the Japan Meteorological Agency (JMA) started to monitor a tropical depression, that had developed within an area of low-moderate vertical windshear about 1,300 km (810 mi) to the east of Manila in the Philippines.

[5] On September 17, The JTWC upgraded Usagi to a tropical storm, as the system continued to consolidate and wrap tighter when slowly tracking westward along the extreme southern periphery of the subtropical ridge.

[11] However, sustained winds up to 180 km/h (110 mph) and the atmospheric pressure at 923 hPa (27.26 inHg) were recorded on Basco, Batanes when the eyewall passed the municipality.

[12] Later, as the eyewall replacement cycle had completed, the eye became cloud-filled, although the environment remained favourable with excellent radial outflow and low vertical wind shear.

[14] At 11:40 UTC (19:40 CST), Typhoon Usagi made landfall over Shanwei, Guangdong, China with 10-minute maximum sustained winds at 85 knots (155 km/h, 100 mph) and the atmospheric pressure at 935 hPa (27.61 inHg).

[17] Early on September 17, PAGASA issued the public storm warning signal number 1 for Cagayan, Calayan and the Babuyan island groups, however these were lifted later that day as Usagi was expected to remain almost stationary for 24 – 36 hours.

[18][19] PAGASA subsequently reissued warning signal number 1 for Cagayan, Calayan, Isabela and the Babuyan island group, during the next day after the system became a typhoon and started moving again.

However, both airlines announced that flights to and from Hong Kong International Airport would be cancelled starting 6 p.m. September 22 and resume the next day if conditions allow.

[28] It made landfall near Shanwei of the Chinese Guangdong province, and passed to the north of Shenzhen, heading northeast.

Even though Usagi caused a direct hit as it skirted at 80 km north of the Hong Kong Observatory Headquarters, the city faced only faced the strongest storm of the year, with northwest gales affecting many places including Victoria Harbour, Airport, Lau Fau Shan and Tai Mei Tuk, as well as occasional storm-force winds that were limited to Cheung Chau and some offshore areas.

Usagi's closest point of approach to Macau is 100 km to the north-northeast, at 4:00AM on September 23, which means that it was barely a direct hit.