Typhoon Haikui

Pre-Landfall 1 | Summary
Posting Date: August 7, 2012, 2:00:00 PM

Current Situation Residents along coastal cities in eastern China are preparing for their third typhoon in less than a week. Just last weekend, two powerful typhoons—Damrey and Saola—came ashore less than 10 hours apart, killing 23 people and causing widespread, if moderate, wind damage. Meanwhile, Typhoon Haikui, the 11th tropical storm of the Pacific season, has been upgraded to a severe typhoon. As of the Japan Meteorological Agency’s (JMA) 15:45 UTC advisory on August 7, the typhoon is located approximately 420 kilometers south-southeast of Shanghai, China, moving 10 km/h in a northwest direction. Haikui is a large storm with radius of storm-force winds around 180 km. Maximum 1-min sustained wind speeds are 140 km/h (with gusts up to 175 km/h), making it a Category 1 hurricane on the Saffir-Simpson scale. The typhoon prompted the China Meteorological Administration to raise the storm warning system to red alert status—its highest level—indicating hurricane-force winds of 118 kilometers (73 miles) an hour or more. In advance of Haikui’s arrival, more than 620,000 people living in the Yangtze River Delta region have been evacuated from their homes. More than 30,000 ships had been called back to shelter in ports. According to local officials, the city’s two main airports had cancelled more than 150 flights and shipping ports were also suspending operation. Shanghai has banned all outdoor group activities, closed all city parks and suspended summer classes. Forecast Track and Intensity The storm is expected to maintain its present northwest movement as it churns toward the eastern coast of China. Typhoon Haikui is forecast to weaken slightly before making landfall as a weak Category 1 storm just north of Wenzhou, Zhejiang province at 8 pm EDT this evening (0000 UTC). Because of the storm’s large size, the duration of damaging winds will likely be more than 24 hours in many coastal locations. Haikui is then expected to weaken further as it moves inland, reaching Hangzhou within 12 hours of landfall and possibly Shanghai within the next 24 hours. Typhoon Haikui is tracking a path similar to another storm that wreaked havoc a few years ago in nearly the same region. In August 2004, Typhoon Rananim made landfall just south of where Haikui is expected, and brought high winds and heavy rain to Wenzhou. Maximum one-minute sustained winds as high as 160 km/h were observed 50 km to the right of Rananim’s center, and higher gusts were likely. Rananim had a narrow precipitation shield, but heavy precipitation rates near landfall caused nearly 400 mm to fall in Linhai, located in the central Zhejiang province. Rananim was the strongest typhoon in the area since Winnie (1997), and caused at least 100 deaths, damaged or destroyed over 130,000 homes and left 270,000 hectares of farmland in ruins. If Rananim were to recur today, AIR estimates insurable losses would be approximately RMB 6 billion, while insured losses would be around RMB 1 billion. Flood Hazard Due to the slow-moving nature of Haikui, the China Meteorological Administration is expecting that the outer bands of the systems will bring torrential rain across the island and strong winds to coastal cities. According to current measurements from Tropical Rainfall Measuring Mission satellites, total accumulated precipitation of 200–300 mm is likely in parts of Zhejiang, Jiangsu, Anhui and the municipality of Shanghai. If the storm system stalls over the area, total rainfall from the storm could top 500 millimeters in some areas. China’s mountainous coast may enhance precipitation on the north and east sides of Haikui on its approach to China, creating significant flood and landslide hazards. In Zhejiang, waves up to 5.9 meters high have been reported along the coast of Xiangshan, a coastal area of Ningbo, forcing thousands of vessels to seek refuge. Since the late 1940s, China has continued to strengthen flood control measures. To that end, more than 280,000 km of embankments, 86,000 reservoirs, and 97 key flood retention areas have been completed to protect the country against future flood losses. Thus, flood risk in China depends on both the accumulated runoff (which is a function of precipitation level, topography, and soil conditions) and flood defenses, which vary by region. Exposure at Risk Yesterday, August 7, Haikui tracked through the northern Philippines, dropping copious amounts of rainfall across the region. Dams in all affected areas reached their critical level, prompting authorities to open several gates, which also flooded several nearby areas. In Quezon City, rainfall accumulations reached 222 millimeters within a 24-hour period. The flooding crippled transport links in the capital, forcing the closure of schools, offices and financial markets. More than nine million people live near Wenzhou in the Zhejiang province—the anticipated landfall location. Historically, adobe and brick with wood-frame have been the predominant construction types for single family homes in China, and they are still widespread in rural areas. These are usually poorly engineered structures and generally not insured. Insured single-family homes are predominately confined masonry and reinforced concrete. Concrete is less vulnerable to flood loads, and also to lateral wind loads. The vulnerability of buildings to flood damage also varies by construction type. For a given flood depth, a residential wood-frame building is expected to sustain more damage than a residential masonry building. Concrete construction is less vulnerable to flood than steel (which may experience surface corrosion and rust-induced expansion) or masonry structures (whose weak connections between building elements makes it permeable to water). Concrete buildings have a strong frame structure, but may suffer from cracking and rebar expansion. Commercial buildings usually have stronger foundations than residential buildings, and are thus better able to resist flood loads. Furthermore, flood vulnerability varies by building height. Because damage is usually limited to the lower stories of a building, high-rise buildings will experience a lower damage ratio—the ratio of the repair cost and the total replacement value of the building—than low-rise buildings because a smaller proportion of the building is affected. Building contents are also extremely vulnerable at lower levels of homes once doors or windows are broken. The AIR tropical cyclone team is monitoring Typhoon Haikui closely and will provide updates as warranted by events.

Pre-Landfall 1 | Downloads
Posting Date: August 7, 2012, 2:00:00 PM