Typhoon Yunya

After a month without any activity in the Western Pacific, a weak tropical depression (with winds of only 10 knots) developed just east of the Philippines and south of the Tropical Upper Tropospheric Trough on June 11. Located in an area of little wind shear, it headed southwestward, developing spiral-band outflow and becoming a tropical storm on the 12th. As a small central dense overcast (CDO) developed over Yunya, it rapidly developed, becoming a typhoon on the 13th as it paralleled the eastern Philippines. The mid-level ridge forced Yunya westward, where it briefly reached a peak intensity of 120 mph (195 km/h) winds on the 14th. Subsequently, the eastward building of the subtropical ridge produced unfavorable vertical wind shear that weakened Yunya to a minimal typhoon before hitting Dingalan Bay, Luzon early on the 15th. Yunya left Luzon as a minimal tropical storm at Lingayen Gulf. It turned northward due to a break in the ridge, and dissipated on the 17th near southern Taiwan due to the vertical shear. Yunya would normally have been an uneventful cyclone, but for the day it hit Luzon, was when the colossal eruption of Mount Pinatubo took place. The ash cloud that normally would have been dispersed across the oceans was redistributed over Luzon by the cyclonic winds of the typhoon, greatly exacerbating the damage caused by the eruption. The water-laden ash fell over the evacuated Clark Air Base, as well as the rest of Luzon, resulting in downed power lines and the collapse of flat-roofed buildings. In some areas it was practically raining mud.

Yunya exited Luzon through the Lingayen Gulf as a weak tropical storm and then turned north toward a break in the subtropical ridge. The system continued to weaken due to the strong vertical wind shear. It then brushed the southern coast of Taiwan as a tropical depression and finally dissipated before it could complete full recurvature into the mid-latitude westerlies. Yunya directly caused one death from the flooding and heavy rainfall it left.[2]