Powerful Typhoon Namtheun to threaten Japan with flooding rain, damaging winds

By Kristina Pydynowski, Senior Meteorologist

September 2,2016; 9:27PM,EDT

 

Namtheun has strengthened into a powerful typhoon as it barrels toward Japan's northern Ryukyu Islands and Kyushu with destructive winds and flooding rain.
Namtheun, equivalent to a Category 3 hurricane, will remain a dangerous typhoon as it tracks through the northern Ryukyu Islands. A track near or just over Yakushima Island is expected before Namtheun impacts Kyushu, weakening in the process.
Further strengthening is possible as Namtheun approaches the northern Ryukyu Islands into Saturday, potentially increasing its strength to that of a Category 4 hurricane.
Namtheun will hit or make its closest approach to the far-northern Ryukyu Islands on Saturday afternoon, local time before grazing and moving into Kyushu on Saturday night and Sunday.

The storm will unleash strong, damaging winds. Namtheun could make a direct hit on Yakushima and the southwestern tip of Kyushu with destructive gusts in excess of 190 km/h (118 mph).
Wind gusts of 95-145 km/h (60-90 mph) can be expected in the far-northern Ryukyu Islands and western Kyushu. Residents should prepare for widespread tree damage, power outages and some structural damage.
"Namtheun is a small and compact typhoon, so its winds do not extend far beyond its center," AccuWeather Meteorologist Adam Douty said.
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The winds will drive the ocean's water onshore, leading to an inundating storm surge and severe coastal flooding.
Wind gusts of 65-95 km/h (40-60 mph) will shift to westernmost Honshu on Sunday night and Monday as Namtheun heads into the Sea of Japan. However, if Namtheun picks up speed, the winds could blast the area on Sunday.
In addition to strong winds, Namtheun will unleash torrential rain with a significant risk of flooding and mudslides. Rain totals will average 100-200 mm (4-8 inches) across the northern Ryukyu Islands and Kyushu this weekend.
This is a closeup live loop of Namtheun. (NOAA/Satellite)
If Namtheun maintains slow forward movement, totals of 200 mm (8 inches) will be widespread with localized higher totals, especially in higher terrain.
As Namtheun turns to the northeast, downpours will also bring a localized flash flood risk to Shikoku and western Honshu late in the weekend and on Monday.

Such a turn will spare South Korea from a direct hit from Namtheun. Heavy rain indirectly linked to the typhoon's moisture that poured down on Friday night will end early in the weekend.
Namtheun is also expected to bypass the areas hit hardest by Lionrock in northern Honshu Island early next week.
Instead, downpours should unfold across Hokkaido and Russia's Maritime territory as Namtheun merges with a non-tropical system over the Sea of Japan. Flash flooding may result, especially where Lionrock recently saturated the ground.