On September 13, the system attained its peak intensity with maximum sustained winds of 125 mph (205 km/h),[nb 1] and a barometric pressure of 900 mbar (hPa; 26.58 inHg), becoming the strongest typhoon in the Western Pacific Ocean since Megi in 2010.

Passing just to the west of Japan, Sanba caused extensive losses to agriculture, forestry, and fishing industries on the islands of Okinawa Prefecture.

In North Korea, the heavy precipitation worsened preexisting flood conditions initially started by Tropical Storm Khanun two months prior.

On September 9, the Joint Typhoon Warning Center (JTWC) started to monitor an area of convection approximately 150 nautical miles (280 km) to the east of Palau.

[3] As it continued to organize, the JTWC issued a Tropical Cyclone Formation Alert (TCFA) on the system at 14:00 UTC on the same day.

[7] Nine hours later, the JTWC also upgraded Sanba to a tropical storm, as its convective banding deepened and wrapped tighter to its low-level circulation center.

[13] Sanba ultimately reached its peak intensity at 18:00 UTC that same day, with 10-minute sustained winds of 110 knots (205 km/h; 125 mph) and a central pressure of 900 hectopascals (27 inHg), according to the JMA.

[14] The JTWC estimated Sanba to have 1-minute sustained winds of 155 knots (285 km/h; 180 mph), making the storm a Category 5-equivalent super typhoon.

[10] On September 14, Sanba showed signs of undergoing an eyewall replacement cycle, as concentric rings were seen in microwave imagery.

[20] Sanba then further weakened to a Category 2-equivalent typhoon, as higher amounts of wind shear began affecting its northwestern quadrant, along with decreasing sea surface temperatures.

[24] The JMA downgraded Sanba to a severe tropical storm 3 hours later, before the JTWC subsequently issued their final advisory on the system.

[29] Locally known as Karen, it enhanced the southwest monsoon affecting the Philippines, which caused flooding over parts of Metro Manila on September 15.

[34] Heavy rains from the storm in Gifu Prefecture triggered numerous landslides and caused significant flooding that washed out hundreds of roads.