Typhoon Nangka Bearing Down on Japan; Landslide Warnings Issued, Feet of Rain Expected (FORECAST)

Jon Erdman
Published: July 15,2015



 
Japan is bracing for major flooding and dangerous landslides as Typhoon Nangka churns toward its heavily populated mainland. The storm's path is likely to 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 (900 millimeters) of rainfall.
In terms of winds, Nangka is the equivalent of a Category 1 on the Saffir-Simpson Hurricane Wind Scale. Maximum sustained winds are 90 mph (40 meters per second) with gusts to 125 mph (55 meters per second), as of 11 a.m. Thursday local time, according to the Japan Meteorological Agency. (Japan is 13 hours ahead of U.S. Eastern Daylight Time.)
At that time, the center of Nangka was 145 miles (230 kilometers) south of Cape Muroto, which is on the Pacific coast of Shikoku, one of Japan's four main islands. Nangka was moving to the north-northwest at 14 mph.

Enhanced Satellite: Nangka

Nangka has been fighting dry air to its north and northwest, which weakened its eyewall convection Wednesday. However, convection managed to wrap back around the center Thursday morning (local time). Satellite data suggested the weakening trend had stopped or even reversed by late Thursday morning, but official forecasts do not call for any significant strengthening before landfall.

Nangka Forecast Path

In any case, there is plenty of moist air in the eastern semicircle of the storm, and unfortunately that is the half where those moist winds are blowing 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, and concern for locally flooding rain and mudslides is rising.
Outer rainbands have already spread across much of Honshu well in advance of Nangka's core circulation, bringing rainfall rates in excess of 2 inches (50 millimeters) per hour.
The Japanese Meteorological Agency has already issued flood warnings for much of the Greater Tokyo area as well as several other prefectures. In addition, as of late Thursday morning JMA had issued landslide warnings for Tokyo as well as for Tochigi, Saitama, Kanagawa and Yamanashi prefectures.
Ominously, the core of Nangka itself will bring additional heavy rain along its path through parts of western and central Japan. In its 11 a.m. JST bulletin Thursday, JMA forecast the following additional rainfall amounts for the 48-hour period ending at noon local time on Saturday:

• Kinki and Tōkai regions (central Honshu, including Osaka and Nagoya): 800 to 900 millimeters (31 to 35 inches)
• Shikoku island: 800 millimeters (31 inches)
• Kantō region (Greater Tokyo): 400 to 500 millimeters (16 to 20 inches)
• Chūgoku region (western Honshu, including Hiroshima): 300 to 450 millimeters (12 to 16 inches)
• Tōhoku region (northern Honshu, including Sendai): 250 to 350 millimeters (10 to 14 inches)

JMA has also has hoisted warnings for high waves for the Pacific coastal prefectures from Tokyo Bay westward as well as several prefectures around the Seto Inland Sea.
Nangka appears headed for landfall on Shikoku late Thursday evening, local time, most likely as a Category 1 equivalent typhoon.

Nangka Wind Potential

The core of its strongest winds, most likely to down trees and trigger power outages, is likely to track through Shikoku and western Honshu from early Friday morning through Friday afternoon.
JMA is forecasting the following maximum wind speeds:

• Shikoku island: 80 mph gusting to 110 mph (35 gusting 50 meters per second)
• Chūgoku and Kinki regions (Osaka, Hiroshima): 65 mph gusting to 100 mph (30 gusting 45 meters per second)
• Northern Kyūshū island: 55 mph gusting to 80 mph (25 gusting 35 meters per second)
• Southern Kyūshū island: 50 mph gusting to 80 mph (23 gusting 35 meters per second)
• Tōkai region (Nagoya): 45 mph gusting to 65 mph (20 gusting 30 meters per second)

The Greater Tokyo area may see tropical storm-force gusts, with some power outages and tree limbs down.
(FORECASTS: Okinawa | Nagasaki | Tokyo)
Nangka should weaken quickly to a post-tropical low as it is picked up by the jet stream, curling northeast over the Sea of Japan, then over 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)