On December 2, an area of convection was spotted by the Joint Typhoon Warning Center southeast of Chuuk. Although convection decreased in the next few hours, on December 5 the JTWC once again noted flaring deep convection, and late on December 6 a Tropical Cyclone Formation Alert was issued. On the morning of December 7, both the JTWC and Japan Meteorological Agency-RSMC Tokyo reported that a tropical depression had formed. Soon after, the depression entered the area of responsibility of PAGASA, who named it Seniang. The depression strengthened throughout the day, and the JMA upgraded it to Tropical Storm Utor later that day. The name Utor was submitted by the United States on behalf of the Marshall Islands, and is a Marshallese word for squall line. Signal no. 3 has been raised in the provinces of Cebu, Leyte, Samar Provinces.