Kind of a strange question! The fact that "this hurricane stands in your direct path to the next port of destination" doesn't mean that you have to follow that direct path. If the hurricane is not moving, just go around it at 60 miles from the eye so that you never have winds greater than 30 knots! But if the captain really insists upon going straight through a hurricane (remind me never to use that cruise line) you can use that formula you give, at radius= 60, then, where the wind speeds will be highest, just before the eye, radius= 20 and set them equal. Both of those involve the unknown mass but it will cancel out.