While Tropical Rainstorm Fung-wong will continue to lash parts of Honshu with heavy rain into Thursday, the next threat to Japan has already developed.
A broad area of low pressure that produced showers and thunderstorms near the Mariana Islands this week has strengthened into Tropical Storm Kammuri.
As the cyclone wraps up and continues to strengthen over the next couple of days, it will track to the northwest keeping the worst impacts to the north of Guam.
Guam can expect periods of rain through Thursday with some gusty winds.
Kammuri will continue to the northwest this weekend through the open waters between the Mariana Islands and Japan over an area that will likely allow the storm to strengthen into a typhoon.
The key to the movement of this cyclone in the long term will be a trough that is still more than 1,000 of miles west of Japan in Siberia. This trough will quickly move eastward and interact with the cyclone early next week.
The faster this trough arrives, the sooner the cyclone will turn north and then northeast with a greater chance to avoid landfall in Japan.
If the trough is slower to interact with the cyclone, then the cyclone will be able to advance farther west before turning to the north and northeast which could result in landfall of a powerful typhoon in southern or eastern Japan.
At this time it appears the trough will arrive quickly enough to turn Kammuri to the northeast Sunday into Monday, causing it to pass east of Japan.
Even if the cyclone does pass east of Japan, the outer bands of the storm could lash eastern Honshu with a few downpours and gusty winds depending on the exact track.
People living in or traveling to Japan should closely monitor the track of this organizing cyclone in the coming days. The most likely time frame for impacts on Japan would be Monday and Tuesday of next week.