Complex sentence: On September 19, Karl continued to strengthen, maintaining a well-defined eye, and strengthening late that day into a Category 4 hurricane with winds of 135 mph (215 km/h) and a minimum pressure of 948 mbar.
Split into simpler sentences: On September 19, Karl continued to strengthen, maintaining a well-defined eye. Late on the September 19, the storm strengthened into a Category 4 hurricane with winds of 135 mph (215 km/h) and a minimum pressure of 948 mbar.