Complex sentence: A few days later, the upper-level low detached from the trough and moved southwestward over the Caribbean Sea, allowing for an upper-level ridge, or high pressure area, to form over the tropical wave.
Split into simpler sentences: A few days later, the upper-level low detached from the trough and moved southwestward over the Caribbean Sea. This allowed for the formation of an upper-level ridge, or high pressure area, over the tropical wave.