Typhoon Jelawat

Landfall | Summary
Posting Date: September 30, 2012, 9:30:00 AM

Current and Forecast Conditions

According to the Japan Meteorological Agency (JMA), Typhoon Jelawat made landfall around 6:00 UTC today in southern Wagayama prefecture with a minimum central pressure of 965 mb and ten-minute sustained wind speeds estimated at 70 knots, making it a Category 1 on the Saffir-Simpson intensity scale. 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 extratropical 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 1-minute sustained) with gusts as high as 36.4 m/s (81 mph) were observed in Shionomisaki, in southern Wagayama prefecture while peak 10-minute sustained wind speeds of 21.0 (53 mph 1-minute sustained) with gusts to 36.1 m/s (81 mph) 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. Flooding is always a concern with landfalling tropical cyclones and this is certainly true of Jelawat. However, due to the storm’s forward speed (55 km/h), precipitation amounts have been limited to 100 to 200 mm, 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 extratropical transitioning as it emerges back over the northwest Pacific Ocean. Before making landfall on Japan’s main island of Honshu, Jelawat made landfall in Okinawa yesterday, the third such typhoon to do so this year. 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, 1-minute sustained). Peak 10-minute winds were as high as 40 m/s (103 mph 1-minute sustained) with a wind gust of 61.2 m/s (137 mph) observed at Naha. Nearly every observing station in Okinawa, and the surrounding islands, experienced peak 10-minite winds exceeding 30 m/s (77 mph) and wind gusts exceeding 50 m/s (112 mph).

Reported and Expected Damage

At the wind speeds recorded on Okinawa, some damage can be expected. Early footage shows flooded streets, downed trees, blowing signage, and even an automobile that was picked up by a strong gust and overturned. Windows broken by flying debris will result in damage to the contents within. Local officials report that 600 buildings have sustained some damage or are flooded. Okinawa’s building stock is predominantly concrete, so significant structural damage from wind should be limited. Thousands are reported to be without power. 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. The AIR tropical cyclone team continues to monitor Typhoon Jelawat closely and will issue additional updates tomorrow, after the storm has exited Japan.

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Posting Date: September 30, 2012, 9:30:00 AM