Typhoon Jelawat Hits Okinawa; Moves on Tokyo: AIR Analysis

By | October 1, 2012

Typhoon Jelawat remains a powerful storm, even if its wind speed has decreased from around from 155 mph, 250km/h, it passed over Okinawa on Saturday with wind speeds over 90 mph, 144 km/h, causing extensive damage, and injuring more than 50 people. It was the third typhoon to strike the island during the current tropical cyclone season

AIR Worldwide reported that the Japan Meteorological Agency (JMA), said Jelawat made landfall on Sunday in southern Wagayama prefecture with a minimum central pressure of 965 mb and ten-minute sustained wind speeds estimated at 70 knots – 80.55 mph, app. 129 km/h – making it a category one cyclone on the Saffir-Simpson intensity scale.

According to AIR, “over the previous 12 to 24 hours, as Jelawat approached mainland Japan, it encountered cooler ocean temperatures and substantially higher vertical wind shear in response to a mid-latitude trough over the northern Sea of Japan. As a result, Jelawat was weakening and undergoing extra tropical transitioning at the time of landfall, with most of the convection located north of the storm center. Observations in southern Wagayama and Aichi prefectures support the JMA central pressure estimates of 965 to 970 mbs.

“Peak 10-minute sustained wind speeds of 20.3 m/s (52 mph, 83km/h, 1-minute sustained) with gusts as high as 36.4 m/s (81 mph, 130 km/h) were observed in Shionomisaki, in southern Wagayama prefecture while peak 10-minute sustained wind speeds of 21.0 (53 mph, 85 km/h, 1-minute sustained) with gusts to 36.1 m/s (81 mph, 130 km/h) were observed in Omaezaki, in southern Shizuoka prefecture. These types of wind speeds were restricted to the coast, however. As Jelawat moved inland, interaction with mountainous terrain has weakened the storm’s winds still further.

AIR also explained that “flooding is always a concern with land falling tropical cyclones and this is certainly true of Jelawat. However, due to the storm’s forward speed (31 mph, 55 km/h) precipitation amounts have been limited to 100 to 200 mm [app. 4 to 8 inches], and similar amounts are expected in regions further to the north. As a result, widespread flooding is not expected, but some localized flooding is likely.

“Jelawat is forecast to continue to weaken and should complete extra tropical transitioning as it emerges back over the northwest Pacific Ocean.”

AIR noted that “three tropical cyclones have made landfall in Okinawa only twice since 1951, but never three typhoons. Furthermore, these three typhoons were successive, impacted the island within 5 weeks of each other, and are amongst the five most intense to make landfall (based on central pressure). Thus, this is a very rare occurrence.

“Naha, the capital of Okinawa prefecture, observed a minimum sea level pressure of 947.7 mb while Nago, a few dozen kilometers to the north, observed a minimum pressure of 948.6 mb; these support JMA central pressure estimates of 935 mb.

“Unlike Typhoon Bolaven, which made landfall on Okinawa on August 26, and to a lesser extent Sanba, which crossed the island three weeks later, observed wind speeds from Jelawat were in line with the JMA estimates (115-120 mph, 184 to 192 km/h, 1-minute sustained). Peak 10-minute winds were as high as 40 m/s (103 mph, 165 km/h, 1-minute sustained) with a wind gust of 61.2 m/s (137 mph, 220 km/h,) observed at Naha. Nearly every observing station in Okinawa, and the surrounding islands, experienced peak 10-minite winds exceeding 30 m/s (77 mph, 123 km/h) and wind gusts exceeding 50 m/s (112 mph, 179 km/h).”

AIR indicated that due to the force of the wind speeds recorded on Okinawa, “some damage can be expected. Local officials report that 600 buildings have sustained damage or are flooded. Okinawa’s building stock is predominantly concrete, so significant structural damage from wind should be limited.

“Although wind speeds were significantly lower on Japan’s main island, the building stock is more vulnerable. Some damage to roof coverings can be expected (roofs on Okinawa are generally concrete slab) in addition to damage to signage, awnings and other non-structural elements.

Source: AIR Worldwide

Was this article valuable?

Here are more articles you may enjoy.