Despite no longer being a super typhoon, Halong still poses serious dangers to lives and property across Japan.
The strength of Halong is expected to be equivalent to that of a strong Category 1 or a minimal Category 2 hurricane as it grazes Kyushu and slams into western Shikoku Saturday local time.
Maximum sustained winds at that time will be 135 to 160 kph (85 to 100 mph).
The dangerous typhoon will impact Japan much sooner.
While the outer rain bands and winds graze Okinawa and Kadena Air Base, rain, wind and pounding surf will increase from south to north across the rest of the Ryukyu Islands through Friday night.
Conditions will then deteriorate in a similar fashion across Kyushu, Shikoku and western Honshu Friday night through Saturday evening as Halong approaches, then crosses mainland Japan.
Eastern Kyushu, Shikoku and western Honshu are bracing for the worst of Halong with widespread flooding rain, damaging winds and an inundating storm surge.
Rainfall amounts will top 150 mm (6 inches) with widespread wind gusts between 95 and 130 kph (60 and 80 mph). Destructive wind gusts between 130 and 160 kph (80 and 100 mph) will slam the southern coasts of Shikoku and western Honshu (in the vicinity of Fukuyama and Okayama).
If Halong moves onshore as a Category 2 hurricane, wind gusts to 175 kph (110 mph) are possible along the coast just east of its landfall site.
The torrential rain from Halong can alone cause severe flooding and mudslides. However, recent torrential rain from Tropical Storm Nakri and a stalled frontal boundary have exacerbated the danger.
One location in Kochi Prefecture measured a record 1,186 mm (46.69 inches) in 72 hours, ending on Tuesday, according to information from the Japan Meteorological Agency.
Earlier in the week, AccuWeather.com Meteorologist Eric Leister reported that Nakri brought 250-500 mm (10-20 inches) of rain to some places in Kyushu and Shikoku, according to observation sites across these islands. Multiple locations received more than 10 inches within a single day.
Tokyo will escape Halong's worst but will still be subject to 25 to 50 mm (1 to locally 2 inches) of rain and wind gusts to 80 kph (50 mph) over the weekend. The strongest winds will howl Saturday night and could cause sporadic power outages and tree damage.
Later in the weekend, western and southern Japan will dry out as Halong tracks through the Sea of Japan and loses it tropical characteristics.
The storm will still be capable of producing potentially flooding rain and damaging winds of 65 to 95 kph (40 to 60 mph) across the northern Japanese islands of Honshu and Hokkaido and the coast of Russia's Maritime Territory and southern Sakhalin Island.