The predecessor to Typhoon Utor was first noted by the Joint Typhoon Warning Center (JTWC) as a cluster of thunderstorms southeast of Chuuk on December 2. Over the next few days, a center of circulation accompanied by intermittent shower activity began to develop in the presence of favorable conditions. At 00:00 UTC on December 7, the Japan Meteorological Agency (JMA) determined that the disturbance had become sufficiently organized to be considered a tropical depression; at the time the cyclone was centered 175 km (110 mi) west-southwest of Yap. Tracking westward under the influence of a powerful subtropical ridge to its north, the depression strengthened into a tropical storm at 18:00 UTC. In accordance, the storm was given the name "Utor"; this name had been submitted by the United States and means "squall line".