A large monsoon trough was anchored south of Guam towards the end of July. By July 21, three areas of disturbed weather had formed. Although the westernmost disturbance dissipated, the easternmost two continued to develop, one of which would later become Typhoon Andy. A Tropical Cyclone Formation Alert (TCFA) was issued for the easternmost system at 1900 UTC on July 21 as sea level pressures fell and convection increased within the vicinity of the disturbance. After becoming better organized, the Japan Meteorological Agency (JMA) started monitoring the system. Later on July 22, the Joint Typhoon Warning Center (JTWC) started monitoring the same system as it developed rainbands and a further increase in thunderstorm activity. Initially, the JTWC correctly predicted the low to move northwest. Hurricane Hunters indicated that the low and mid-level centers were not vertically aligned. On July 23, both the JMA and JTWC upped the depression into a tropical storm. Bess then began to intensify. At 0600 UTC on July 24, Bess was upgraded to a severe tropical storm by the JMA. After the formation of an eye, both agencies classified Bess as a typhoon.