sentences:  The JTWC recognized the northward model bias, which was described as under-analyzing the strength of the subtropical ridge.By April 16, the typhoon attained the equivalence of a Category 3 tropical cyclone on the Saffir-Simpson Hurricane Scale, and despite a potential threat to Guam the typhoon remained 260 km (160 mi) south of the island.It gradually curved to the north, and on April 20 JTWC classified Super Typhoon Isa as reaching peak 1-min winds of 270 km/h (165 mph).