SUNDAY, SEPTEMBER 24, 2017
Typhoon Noru
8/7/2017 1:00:00 PM
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Landfall 8/7/2017 1:00:00 PM 
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Posting Date: 8/7/2017 1:00:00 PM

Typhoon Noru made its first landfall in Yakushima, an island in Kagoshima Prefecture, Japan, at 18:00 UTC on August 5, 2017, as a Category 1-equivalent storm, with maximum sustained 1-minute winds of 120 km/h and a minimum central pressure of 970 mb. It then continued northwestward, weakening before its second landfall near Kainan City in Wakayama Prefecture, Japan, on August 7 at around 07:00 UTC as a tropical storm, with maximum sustained 1-minute winds of ~101.7 km/h and a minimum central pressure of 975 mb. At 09:00 UTC on August 7, Noru had maintained its strength as it tracked farther inland, moving through Osaka Prefecture and into Nara Prefecture. By 12:50 UTC on August 7, it had weakened to a tropical depression over Shiga Prefecture.

newsalert for typhoon noru 20170807 track map.png
Track map of Typhoon Noru as of 12:00 UTC on August 7, 2017. (Source: JMA)

Meteorological Summary

Noru was the fifth tropical cyclone to form in the West Pacific Basin this typhoon season, developing first as a tropical depression on July 20 and then intensifying between July 29 and 30 from a tropical storm to a Category 5-equivalent storm—the strongest this year to date—after engulfing Tropical Cyclone Kulap in a rare instance of the Fujiwhara effect. Noru then weakened to the equivalent of a Category 3 storm on August 3 as it passed over colder waters and moved northwestward toward southern Japan. It continued to weaken as it tracked farther northward through August 4, reaching Category 2 equivalency. Noru weakened to a Category 1-equivalent storm before making its first landfall in Kagoshima Prefecture on the island of Yakushima, after which it turned northeastward. The storm experienced slow and steady weakening before making its second landfall in Wakayama Prefecture, near the city of Kainan, on the main island of Japan.

More than 635 mm of rain fell in 72 hours in the city of Naze, Kagoshima Prefecture, as of August 7; the town of Tokushima measured more than 330mm of rain in just 24 hours. Despite its continued weakening to a tropical depression on August 7 as it tracked farther northwestward along the middle of Honshu, heavy rainfall remains a concern and could trigger flooding and landslides. Rainfall totals could reach 500 mm in central Japan as Noru crosses toward the Sea of Japan.

Reported Impact

More than 400 flights were canceled as Noru approached central Japan, according to the country’s public broadcaster NHK, and West Japan Railway Company halted operations of more than 70 express trains. Three oil companies reportedly held back shipments because of the storm. According to daily news service Mainchi Shimbun, around 15,000 people were ordered to evacuate Tokushima Prefecture on August 7, with smaller-scale evacuation orders issued for Wakayama and Kagawa prefectures. Noru’s slow forward movement of 20 km/h is raising the risk of prolonged rainfall. Residents should be prepared for landslides, swollen and overflowing rivers, and high waves, according to the Japan Meteorological Agency (JMA).

Exposure at Risk

Japan has strict and well-enforced construction codes, although many existing structures predate the existence of these codes. Residential exposures in Japan are dominated by wood construction; non-wood residences primarily consist of steel and concrete. Modern wood construction typically demonstrates the best performance in typhoons among all wood constructions in Japan. However, damage to roof coverings and windows can allow wind-driven rain to enter and cause extensive damage to contents. Furthermore, dislodged external components can become wind-borne debris and cause damage to surrounding structures and glazing.

Larger multi-family apartment buildings and commercial and industrial structures are generally engineered and made of reinforced concrete or steel. Complete structural collapse of engineered buildings due to typhoons is extremely rare; damage is usually confined to nonstructural components, such as mechanical equipment, roofing, cladding, and windows.

A significant portion of Japan’s industrial stock is of non-engineered light metal construction, which is one of the construction types most vulnerable to high winds. Low-rise, non-engineered commercial and industrial buildings usually perform similarly to single-family homes under typhoon conditions.

Even with modern flood-control structures, the risk of flood damage remains high in Japan. For a given flood depth/effective surge depth, a residential wood frame building generally will sustain more damage than a residential masonry building. Concrete construction is less vulnerable to flood than steel or masonry. Commercial and apartment buildings usually have stronger foundations than residential buildings, and are thus better able to resist flood loads. Water damage to machinery and contents drives most flood-related loss; also, because damage is usually limited to the lower stories of a building, high-rise buildings will experience a lower damage ratio than low-rise buildings because a smaller proportion of the building is affected.

Forecast Track and Intensity

Noru is forecast to continue weakening as it crosses multiple prefectures along its northwestward track through Honshu over the next 24 hours. A turn northward is expected, after which Noru is expected to move out to the Sea of Japan and dissipate.

Typhoon Noru
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