Complex sentence: Hurricane Fern was the first of four tropical systems to develop in association with an extended surface trough across the Gulf of Mexico into the open Atlantic, along with Ginger, Heidi, and a strong tropical depression.
Split into simpler sentences: Hurricane Fern was the first of four tropical systems to develop from an extended surface trough of low pressure across the Gulf of Mexico into the open Atlantic. The trough developed Hurricane Fern, Hurricane Ginger, Tropical Storm Heidi, and a strong tropical depression.