Complex sentence: At roughly the same time, Helene passed over Newfoundland, with gale force winds having expanded 500 mi (800 km) from the system's center, coinciding with the US Weather Bureau's final advisory on the system.
Split into simpler sentences: At roughly the same time, Helene passed over Newfoundland, with gale force winds having expanded 500 mi (800 km) from the system's center. This coincided with the US Weather Bureau's final advisory on the system.