As surface pressures continue to drop, a
tropical storm becomes a
hurricane when sustained wind speeds reach 64 knots (74 mph).
A pronounced rotation develops around the central core.
Hurricanes are Earth's strongest tropical cyclones. A distinctive feature
seen on many hurricanes and are unique to them is the dark spot found in the
middle of the hurricane. This is called the eye.
Surrounding the eye is the
region of most intense winds and rainfall called the
eye wall. Large bands
of clouds and precipitation spiral from the eye wall and are thusly called
spiral rain bands.