Complex sentence: The following day, the attached cold front dissipated, allowing for the system to intensify, and was upgraded a tropical storm by September 22, following a reconnaissance flight into the system which reported a minimum pressure of 1001 mbar (hPa; 29.56 inHg).
Split into simpler sentences: The following day, the attached cold front dissipated, allowing for the system to intensify. The system was subsequently upgraded a tropical storm by September 22, following a reconnaissance flight into the system which reported a minimum pressure of 1001 mbar (hPa; 29.56 inHg).