 On September 16 , the Japan Meteorological Agency ( JMA ) began monitoring an area of convection as a tropical depression about 1 @,@ 270 km ( 790 mi ) east @-@ northeast of Guam . The depression was located within an area of low to moderate wind shear under an upper @-@ level anticyclone . Flaring convection was noted along the eastern portion of the developing system before the Joint Typhoon Warning Center ( JTWC ) issued a Tropical Cyclone Formation Alert later that day . Early on September 17 , the JTWC began issuing advisories on Tropical Depression 16W . Located within a weak steering environment , the storm executed a clockwise loop while quickly strengthening . Several hours after the JTWC issued their first advisory , the JMA upgraded the system to a tropical storm and gave it the name Yagi ; the name was contributed by Japan , and is the Japanese word for " goat " . Late on September 18 , the JMA upgraded Yagi to a severe tropical storm while the JTWC classified the storm as a minimal typhoon . 
