The water level of a stream is high on the southern island of Jeju as the country braces for Super Typhoon Hinnamnor, Sept. 5. Yonhap
Typhoon Hinnamnor neared South Korea on Monday, forcing cancellations of hundreds of flights and prompting schools to switch to remote learning as the entire nation went on high alert for what could be the most powerful storm ever to hit the country.
The typhoon, the 11th this year, is forecast to edge closest to the southern island of Jeju around 1 a.m. Tuesday and reach the southern coastal region of South Gyeongsang Province around 7 a.m. Tuesday, according to the Korea Meteorological Administration (KMA).
The typhoon's strength when it nears South Korea is expected to become the strongest typhoon ever to make landfall, with an atmospheric pressure of 950 hectopascals at its center, according to the KMA.
"Hinnamnor is a very big typhoon with a radius of 400 kilometers, and can carry strong winds and heavy rainfall almost all across the country," Han Sang-un, the chief forecaster at the KMA, told a press briefing, urging to minimize possible casualties.
As of Monday morning, the typhoon had been located 390 kilometers south-southwest of Jeju's Seogwipo, moving north at a speed of 22 kilometers per hour, with an atmospheric pressure of 930 hectopascals.
The speed is faster than an earlier estimate of 12 km per hour, and the typhoon is classified as a "very strong" typhoon packing a maximum sustained wind speed of 50 meters per second.
Typhoons are classified into four categories: medium, strong, very strong and super strong. Super strong refers to typhoons with a maximum wind speed of at least 54 meters per second.
In this image taken by Korea's geostationary satellite, Chollian-2A, at 7:20 a.m. on Sept. 5, and released by the National Meteorological Satellite Center, Typhoon Hinnamnor is seen moving northward near the country's largest island of Jeju. Yonhap 
