The stadium effect eye is something only seen with the stronger of many hurricanes. It is pretty much what the name says- the eye looks like that of a circular stadium. If you were to fly a plane into the eye, the idea is that you would be able to see the clouds formed in a stadium-style formation.
Sanba is lashing out with winds of 232 kilometers/hour (144 MPH). The Japanese island of Okinawa is at risk from major and potentially devastating effects from Sanba. This threat appears to be verifying, as the outer eyewall appears to be approaching the island. The island of Okinawa can be seen if you look north of the eye, and is shown as an orange outline.