Typhoon Zeb, known in the Philippines as Super Typhoon Iliang, was a powerful typhoon that struck the island of Luzon in October 1998. It is tied with Cyclone Ron and Cyclone Susan in terms of minimum pressure, for the most intense tropical cyclone worldwide for 1998. The tenth tropical storm of the season, Zeb formed on October 10 from the monsoon trough near the Caroline Islands. It moved westward initially and quickly intensified. Zeb's inflow briefly spawned another tropical storm, which it ultimately absorbed. Developing an eye, Zeb rapidly intensified into a super typhoon, officially reaching maximum sustained winds of 205 km/h (125 mph); one warning agency estimated winds as high as 285 km/h (180 mph). After reaching peak intensity, the typhoon struck northern Luzon and quickly weakened over land. Turning to the north, Zeb brushed the east coast of Taiwan at a reduced intensity, and after accelerating to the northeast it moved through Japan. It became extratropical on October 18 and moved eastward over open waters.
First affecting the Philippines, Zeb dropped torrential rainfall in Luzon, reaching in one day in La Trinidad, estimated as a one-in-1,147-year event. The rains caused floods and landslides, which compounded with high winds to leave heavy crop damage. Zeb destroyed or damaged 85,844 houses in the Philippines, and damage in the country was estimated at ₱5.375 billion (1998 Philippine pesos, $126 million U.S. dollars), the fifth-costliest at the time. There were also 83 deaths in the country, a number compounded upon when Typhoon Babs struck the same region a week later. High winds and rainfall from Zeb later affected Taiwan, causing NT$4.15 billion (New Taiwan dollar, $125 million USD) in damage as well as 31 deaths. Gusty winds affected much of Japan, while heavy rainfall peaked at on Mount Ontake. The storm killed 14 people in the country, several related to landslides. Zeb destroyed 770 homes and flooded another 12,548 in Japan.
Meteorological history
The monsoon trough spawned a tropical disturbance over the western Pacific Ocean to the east of Guam around October 7. The system moved steadily westward, organizing enough for the American-based Joint Typhoon Warning Center (JTWC) to issue a Tropical Cyclone Formation Alert early on October 9. After the disturbance passed south of Guam, the JTWC began issuing advisories on Tropical Depression 18W late on October 9, and the Japan Meteorological Agency (JMA) followed suit the next day. While passing north of Yap in the Caroline Islands, the depression intensified into a tropical storm according to the JTWC, which gave it the name Zeb. The JMA again was delayed in upgrading by a day.
After becoming a tropical storm, Zeb proceeded to steadily intensify. Its large inflow spawned a circulation well to the east-northeast, which organized into a separate tropical storm – Alex. Early on October 11, the storm entered the area of responsibility of PAGASA – the Philippine-based weather agency – which gave it the local name Iliang. Late on October 11, the JTWC upgraded Zeb to typhoon status, or one-minute winds of at least . This was based on the appearance of a banding-type eye on satellite imagery. On October 12, the storm rapidly intensified as it turned more to the west-northwest toward the Philippines. During this time, it caused increased wind shear over the smaller Tropical Storm Alex to the east-northeast, ultimately absorbing it. At 00:00 UTC on October 13, the JTWC upgraded Zeb to super typhoon status, estimating winds of , marking that Zeb attained Category 5 status on the Saffir-Simpson scale. Twelve hours later, the agency estimated that the typhoon strengthened further to a peak of 285 km/h (180 mph), making it the strongest storm of the season. At the same time, PAGASA also estimated peak 10-minute winds of , also designating Zeb as a super typhoon. Late on October 13, the JMA estimated peak 10-minute winds of just east of the island of Luzon. While near peak intensity, the JTWC estimated that winds of extended , and gales extended from the center.