The origin of Hurricane Wilma is complicated. During the second week of October, an unusually large, monsoon-like lower-level circulation and a large area of disturbed weather developed over much of the Caribbean Sea. The system was enhanced by diffluence—the rate at which a fluid moves—from an upper-level low across the southwestern Atlantic. By October 13, a broad area of low pressure developed and persisted about 150 miles (240 km) southeast of Jamaica, possibly aided by the passage of tropical waves through the area at the time. Convection increased and became slightly better organized, though upper-level wind shear originally stopped development. The system moved westward, and early on October 14 the convection became more concentrated and a little better organized as upper-level wind shear lessened slightly.