During June 1966, low atmospheric pressure stretched across the western Caribbean Sea and Gulf of Mexico—a pattern that is conducive for tropical cyclogenesis. During the first few days of the month, a dissipating trough extended from the southeastern United States into the western Caribbean. A mid-level circulation developed along the trough near Cabo Gracias a Dios on June 3. By the next day, the circulation had reached the surface, which marked the development of a tropical depression over eastern Nicaragua. On June 5, the depression crossed Honduras and emerged into the western Caribbean, moving north-northeastward through an area of warm sea surface temperatures. It had a good cyclonic circulation, convection, and moisture content, but most significantly, a passing trough to the north provided the depression with favorable outflow. On June 6, the depression rapidly intensified into Tropical Storm and later Hurricane Alma. This made it the earliest hurricane in the basin since Hurricane Able in 1951.