Hurricane Joaquin

http://www.livescience.com/52369-hurricane-joaquin-eyewall-replacement.html

Hurricane Joaquin, a Category 4 storm that is currently battering the central Bahamas, appears to be replacing its eye, according to weather forecasters.

New satellite views of the intense hurricane appear to show the storm's eye obscured, which could indicate that a new eye is forming around the old one, NASA said. This process, known as eyewall replacement, occurs naturally in powerful tropical cyclones. (Tropical cyclones that form in the Atlantic or eastern Pacific are called hurricanes, while those that form in the western Pacific and southeastern Indian Ocean are dubbed typhoons.)

During eyewall-replacement cycles, a new outer eyewall — a swirling mass of clouds that rotates around the center of a storm — forms. This eventually cuts off inflow to the existing eye and replaces it altogether. Such an event typically weakens a hurricane, but the replacement can also blow hurricane-force winds over a more sprawling area, according to NASA.