Complex sentence: Proceeding northwest, it maintained this intensity for eight hours, but on September 2 it entered cooler waters and began to weaken, and by September 6 it had degenerated into a remnant area of low pressure.
Split into simpler sentences: Proceeding northwest, it maintained this intensity for eight hours, but on September 2 it entered cooler waters and began to weaken. By September 6 it had degenerated into a remnant area of low pressure.