Emergency warnings were issued by Japan's weather agency on Monday, urging people in the country's southern islands to take maximum precautions against a barreling super typhoon's violent winds and torrential rains, Reuters reported, with the biggest U.S. Air Force base in the Pacific being asked to evacuate some of its aircraft.

Described as a "once in a decades storm," typhoon "Neoguri," which is already gusting at more than 160 miles per hour (270 kilometers) at Japan's Okinawa island chain, may pick up yet more power as it moves northwest, growing into an "extremely intense" storm by early Tuesday and possibly reaching mainland Japan by late Wednesday, the Japan Meteorological Agency (JMA) said. "Please be vigilant, stay inside buildings and avoid working outside and making unnecessary trips," a JMA official said at a press briefing.

The meteorological agency forecast typhoon Neoguri, whose name means raccoon in Korean, would dump up to 80 millimeters (three inches) of rain an hour on Okinawa as it pounds the group of islands, Inquirer.net reported.

Meanwhile, the storm, which could affect an area with a 500 kilometer radius, was expected to be downgraded by the time it hit the Japanese mainland. However, Kyushu region - next to the main island of Honshu where major cities including Tokyo and Osaka are located - was already seeing heavy rains and officials warned over possible floods and landslides.

The agency said Monday evening that it plans to issue an emergency sea warning for Okinawa island, where multiple U.S. military facilities are situated. Although it regularly finds itself in the path of big typhoons, many of the buildings on the island are designed to weather the powerful winds that come roaring in off the Western Pacific. "In these regions, there is a chance of the kinds of storms, high seas, storm surges and heavy rains that you've never experienced before," a JMA official said. "This is an extraordinary situation, where a grave danger is approaching."

Authorities at Kadena Air Base, the largest U.S. military installation in the Asia-Pacific region, said they aren't taking any chances. "I can't stress enough how dangerous this typhoon may be when it hits Okinawa," Brig. Gen. James Hecker, the Commander of the 18th Wing, said Sunday on the base's Facebook page. "This is the most powerful typhoon forecast to hit the island in 15 years."

"I'm calling on the heads of municipalities not to hesitate in issuing evacuation warnings and don't be afraid of being overcautious," Keiji Furuya, the state minister in charge of disaster management, told a government meeting.

Astronaut Reid Wiseman in the International Space Center tweeted a dramatic photo over the weekend of the typhoon viewed from above, showing vast bands of cloud spiraling out from its center. "#Typhoon Neoguri nearing Japan. Takes up our entire view. Wow," he wrote.