Former Typhoon Nangka Lingers Near Japan; 29 Inches of Rain Reported, Landslide Warnings Issued (FORECAST)

Jon Erdman
Published: July 17,2015
Typhoon Nangka made landfall in Japan late Thursday, but even though it has weakened to a tropical depression it is still lashing parts of the country with heavy rainfall as it meanders slowly over the Sea of Japan.
More than 2 feet of rain have been reported some locations, and as rain continues to lash some of 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.
Nangka's center exited Tottori Prefecture and emerged over the Sea of Japan around 3 p.m. local time Friday. Later, JMA said Nangka had weakened to a tropical depression as of 3 a.m. local time Saturday, when it was centered over the Sea of Japan just west of the Noto Peninsula of central Japan's Ishikawa Prefecture.
Because of its slow movement and proximity to land, Nangka is still bringing rainfall to parts of the country.
(MORE: Nangka News/Impacts | Hurricane Central)

Enhanced Satellite: Nangka

Winds have slackened as Nangka has weakened, and there are no longer any areas of impressive convection. Still, moist tropical air is still bringing locally heavy downpours to parts of Japan, generally between Osaka and Tokyo.

Nangka Forecast Path

This is falling on an area where moist winds blew from south to north well before Nangka's arrival as a typhoon, sending a tropical air mass right into Japan's rugged mountains and a stationary front and forcing that moist air to rise and form rain-bearing clouds. That is a common setup for torrential rain far from the center of a tropical cyclone.

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 Saturday morning Japanese time) for much of central Japan . In addition, JMA continues landslide warnings for several prefectures in central and western Japan.
As of 9:20 a.m. JST Saturday, the highest reported rainfall total in Japan was 745.5 millimeters (29.35 inches) in Kamikitayama village, Nara prefecture, south of Osaka. In a testament to Japan's soggy climate, that 72-hour total isn't even a monthly record for that location, despite a recordkeeping period that only goes back 39 years.
JMA hoisted warnings for high waves for the Pacific coastal prefectures from Tokyo Bay westward ahead of the typhoon's arrival. Those warnings, as well as those for coastal sections of Yamaguchi, Shimane and Tottori prefectures on the Sea of Japan coast, have either been canceled or downgraded to advisories.

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 remains a tropical depression, as the strong temperature gradients needed to induce transition to post-tropical status are still well north of its circulation. Nangka is forecast to move in a general northeastward direction through the weekend. This will take its center across northern Honshu and/or southern and eastern Hokkaido before it finally dissipates. Locally heavy rain may fall on those areas this weekend.

Storm History

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, July 10.
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).
As it approached Japan, 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 the weakening trend leveled off prior to its first landfall Thursday night.

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