Typhoon Nangka Makes Landfall in Japan, Prompting Landslide Warnings; 27 Inches of Rain Already Reported (FORECAST)

Jon Erdman
Published: July 16,2015


 
Typhoon Nangka made landfall in Japan late Thursday, but even though it has weakened to a tropical storm the country's weather woes are far from over. More than 2 feet of rain have been reported in one Japanese village, and as torrential rain continues to lash the country's most populated regions, more flash flooding and landslides are expected.
The center of Typhoon Nangka made its first Japanese landfall at 11:07 p.m. Thursday night local time near Muroto city, which is on the Pacific coast of Shikoku, one of Japan's four main islands.
Nangka was the equivalent of a Category 1 tropical cyclone on the Saffir-Simpson Hurricane Wind Scale at landfall with maximum sustained winds estimated at 75 mph, according to both the Japan Meteorological Agency and the U.S. Joint Typhoon Warning Center. (Japan is 13 hours ahead of U.S. Eastern Daylight Time.)
About seven hours later, Nangka made a second landfall after crossing the Seto Inland Sea separating Shikoku from Japan's largest island, Honshu. The second landfall, as a tropical storm, occurred in Kurashiki city, Okayama prefecture.
As of 9 a.m. Japanese Standard Time Friday, JMA said the center of Tropical Storm Nangka was over Niimi city, Okayama prefecture. It was moving north at 10 mph – slower than it had been moving when it made its two landfalls. Maximum sustained winds were 23 meters per second, or about 50 mph.
Major flooding and dangerous landslides are expected as Tropical Storm Nangka affects a large swath of the heavily populated mainland. The storm's path will bring impacts across all four of the nation's largest islands, and the nation's official weather agency is warning that some locations could see up to 3 feet (1 meter) of rainfall.
(MORE: Nangka News/Impacts | Hurricane Central)

Enhanced Satellite: Nangka

Nangka fought off dry air to its north and northwest, which initially weakened its eyewall convection Wednesday.
Satellite imagery confirmed convection managed to wrap back around the center Thursday morning (local time) and any weakening trend had leveled off prior to landfall Thursday night.

Nangka Forecast Path

In any case, there was plenty of moist air in the eastern semicircle of the storm, and unfortunately that is the half where those moist winds blew from south to north, right into Japan's rugged mountains and a stationary front. That is a common setup for torrential rain far from the center of a tropical cyclone.
As of early Friday morning local time, the heaviest rains continued to hammer central parts of Honshu from Wakayama and Nara prefectures northwest through the Osaka and Kobe metropolitan areas. While rainfall rates were not as extreme as those seen Thursday night, some areas are still seeing nearly 25 millimeters (1 inch) of rain per hour.

Current Conditions and Rainfall Intensity

The Japanese Meteorological Agency issued flood warnings for much of the Greater Tokyo area as well as several other prefectures. Warnings remain in effect (as of late Friday morning) for much of the area from Tokyo westward to Osaka, Kobe, and much of the island of Shikoku . In addition, JMA has issued landslide warnings for a number of prefectures in central and western Japan.
As of 10 a.m. JST Friday, the highest reported rainfall total in Japan was 731.5 millimeters (28.80 inches) in Kamikitayama village, Nara prefecture, south of Osaka.
JMA has also has hoisted warnings for high waves for the Pacific coastal prefectures from Tokyo Bay westward to Tokushima Prefecture on Shikoku. High wave warnings were in effect earlier before being downgraded for coastal sections of Yamaguchi, Shimane and Tottori prefectures on the Sea of Japan coast, where onshore winds are occurring to the left of Nangka's northward-moving center.

Nangka Wind Potential

Now that Nangka is over the rugged terrain of Honshu, its circulation is being disrupted and its winds are quickly losing steam. Still, a few geographically favored locations were still seeing sustained tropical storm-force winds as of 10 a.m. JST Friday.

Current and Peak Wind Gusts

The top reported wind gust from Nangka was 95 mph at Cape Muroto, a site whose elevation and position on the Pacific coast make it unusually wind-prone. That gust occurred shortly before midnight Thursday evening. Cape Muroto also reported the highest sustained wind from Nangka and was the only official site to report a sustained typhoon-force wind; that was 75.8 mph (33.9 meters per second) at 12:13 a.m. JST Friday.
High winds did affect more populated areas as well; for instance, Komatsushima Air Base in Tokushima Prefecture clocked a 77-mph wind gust at 3:24 a.m. JST Friday.
(FORECASTS: Nagasaki | Hiroshima | Osaka | Nagoya | Tokyo)
Nangka will continue to weaken quickly to a post-tropical low as it is picked up by the jet stream, curling northeast, then east over the Sea of Japan into northern Honshu or Hokkaido this weekend. Nonetheless, very heavy rainfall is possible in those areas.
Nangka briefly became a super typhoon -- maximum sustained winds reaching 150 mph -- late Thursday into early Friday, before northerly wind shear eroded convection on the north side of the circulation Friday.
According to hurricane specialist Michael Lowry, Wednesday, July 8 marked the first time in over 20 years that three typhoons were active in the western Pacific basin at the same time (Chan-hom, Linfa and Nangka).

MORE: Super Typhoon Maysak Images (March-April 2015)