Bolaven formed as a tropical depression over the western Pacific Ocean on August 20, 2012, and strengthened to a typhoon the following day. By August 24, the U.S. Navy’s Joint Typhoon Warning Center (JTWC) reported that Bolaven was located roughly 410 nautical miles (760 kilometers) southeast of Kadena Air Base, Okinawa, Japan. Bolaven had maximum sustained winds of 115 knots (215 kilometers per hour) and gusts up to 140 knots (260 kilometers per hour). Over the next 24 hours, the JTWC forecast, Bolaven would strengthen to carry maximum sustained winds of 120 knots (220 kilometers per hour) and gusts of 145 knots (270 kilometers per hour).
The Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite captured this natural-color image on August 24. Bolaven had a well-defined eye and spiral arms spanning hundreds of kilometers northeast of the Philippines. The JTWC storm track showed Bolaven traveling northward toward the Korean Peninsula over the next few days.