Complex sentence: Moving slowly eastward, the system redeveloped a new surface circulation on October 21, becoming a tropical depression the next day about 175 mi (280 km) west of Campeche, Mexico.
Split into simpler sentences: Moving slowly eastward, the system redeveloped a new surface circulation on October 21. At that time, it was situated 175 mi (280 km) west of Campeche, Mexico.