While tropical downpours bring the threat of flooding through this weekend to Japan and South Korea, the danger of a typhoon looms for next week.
The immediate concern to these nations is a tropical low spinning in the South China Sea.
Later next week, a new danger will come via Tropical Storm Halong which is spinning westward away from Guam and is on track to become the next typhoon in the western Pacific basin.
The tropical low spinning in the South China Sea has already been classified as Tropical Storm Nakri by the Japan Meteorological Agency, Japan's government source for meteorological information. The Joint Typhoon Warning Center (headed by the United States) has yet to follow suit as the low remains disorganized.
Regardless of its classification, the slow-moving low will cause periods of tropical downpours to spread from the Ryukyu Islands up to Japan's islands of Kyushu, Shikoku and western Honshu and to South Korea through the start of the weekend. Additional rain will continue to stream over most of this area into Sunday.
Flooding and mudslides are a serious concern, especially across southwestern Japan and southern South Korea where several days of downpours will push rain totals through Sunday past 150 mm (6 inches).
Some areas may get the additional rain on Monday, prolonging the flood and mudslide danger.
Any flooding problems in Seoul, where rainfall totals should be on the order of 50 to 100 mm (2 to 4 inches), would likely be localized. Tokyo, meanwhile, will escape the low's downpours.
While the greatest threat from this low will by far be flooding and mudslides, gusty winds between 65 and 80 kph (40 to 50 mph) will whip the northern Ryukyu Islands, the southern coast of South Korea and the southern and eastern coast of Kyushu.
Shanghai, China, will experience some of the outer fringes of the low through the start of the weekend. Downpours and gusty winds are possible with rainfall amounts expected to be between 25 and 75 mm (1 and 3 inches).
While that low will fail to approach typhoon status, Tropical Storm Halong is on track to become the western Pacific basin's next typhoon.
Halong is currently tracking westward away from Guam after AccuWeather.com Meteorologist Eric Leister reported that it dumped more than 10 inches of rain and kicked up a 53-mph wind gust on the island.
Disruptive wind shear (strong winds above the surface that can shred tropical systems apart) will work against Halong's attempts to become a typhoon through the weekend.
If Halong is not a typhoon by Sunday, AccuWeather.com Meteorologist Adam Douty expects the system to definitely reach that status next week as it tracks northwestward and the wind shear lessens.
AccuWeather.com meteorologists will be monitoring the potential for Halong to strengthen rapidly prior to reaching land later next week.
While the current path of Halong puts the northern Ryukyu Islands and southern Japan at greatest risk of a direct landfall with heavy rain and damaging winds, all residents of Japan, the Korean Peninsula and northeastern China should closely monitor the future typhoon for potential dangers and any adjustments to the forecast track.
"Given that southern Japan and the Ryukyu Islands will see heavy rainfall during the next few days, the approach of this second tropical system could spell trouble in the way of major flooding in these areas," Douty warned.