The eye is a region of mostly calm weather found at the center of tropical cyclones and is a well-recognized feature. It is usually circular, typically 30–65 kilometers (19–40 miles) in diameter and is at the cyclone's center of circulation. A cyclone's lowest barometric pressure occurs in the eye, and can be as much as 15 percent lower than the pressure outside the storm. In strong tropical cyclones, the eye is characterized by light winds and clear skies, surrounded on all sides by an eyewall, a normally symmetric ring of towering thunderstorms where the most severe weather of a cyclone occurs. In weaker tropical cyclones, the eye is less well defined, and can be covered by the central dense overcast, an area of high, thick clouds that show up brightly on satellite imagery. Weaker or disorganized storms may also feature an eyewall that does not completely encircle the eye, or have an eye that features heavy rain. (Full article...)