This satellite-based image shows Super Typhoon Sanba in the Philippine Sea on Thursday.
A storm packing 145 mph winds was bearing down on the southern end of Japan's Okinawa Island, where locals and U.S. military personnel were quickly stocking up and battening down.
Typhoon Sanba had winds equivalent to a Category 4 hurricane. (Named storms west of the international dateline in the Northwest Pacific Ocean are called typhoons, not hurricanes.)
Earlier Friday, Sanba's winds had reached 178 mph, making it a "super typhoon" in the jargon of meteorologists. That was the equivalent of a top-rated Category 5 hurricane.
After swiping southern Okinawa this weekend, Sanba is projected to make landfall in South Korea with winds still around 100 mph.
"The center will pass close to Okinawa this weekend and then Sanba, in a less-intense but still potent state, is expected to reach South Korea Sunday night or Monday," weather.com reported.
On Okinawa, the Stars and Stripes news website for U.S. military personnel was reporting that military commissaries were packed with people buying food and emergency supplies.
"We’re already seeing/feeling Super Typhoon Sanba’s most outer bands," the report stated. "If it’s sitting outside the garage, put it inside. If the garage door is still open, shut it. If the trampoline is still up, take it down."
Kadena Air Base, with 18,000 servicemen, is the U.S. facility closest to Sanba and should see winds around 60 mph.
Up to a foot of rain was forecast for the area and satellite data shows that some of Sanba's bands were dumping 3 inches of rain an hour, NASA said in a statement.
Some 80,000 U.S. citizens are on Okinawa, nearly 30,000 of them U.S. military personnel. Okinawa's total population is some 1.3 million people.
More world stories from NBC News:
- Man behind anti-Islam film reportedly is Egypt-born ex-con
- Ex-Navy SEAL killed in Libya respected as highly trained pilot, marksman
- 33,000 told to flee as volcano erupts near Guatemala tourist zone
- Why films and cartoons of Muhammad spark violence
- Australia moves to ban fishing trawler with 900-foot-long net
- Protesters storm US Embassy in Yemeni capital
- Libya pledges to help US catch American officials' killers