This image of the South Pacific on February 16, 2005, shows Cyclone Olaf and a weakening Cyclone Nancy one day before Olaf passed over the island of American Samoa as a Category 5 storm. Although the island received a direct hit, there were no reported causalities on land. However, some fishing vessels may have been lost.
To the north of Olaf, a band of large thunderstorms stretches across the top of the scene. The line of storms is probably an outer spiral band of the cyclone; at the eastern end, the line of storms can be seen bending southward toward the core of the storm. The area of clear skies between the main part of the storm and the outer band of thunderstorms in the north is known as a moat. A moat is zone of sinking air between bands of convection (rising air that fuels thunderstorms.)
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Image courtesy the MODIS Rapid Response Team, NASA-GSFC
