A Reconnaissance Aircraft flight into the system late on October 4 confirmed the existence of a circulation center . A bit later , on October 5 , the Joint Typhoon Warning Center ( JTWC ) called the system Tropical Depression Twenty-Three . A Reconnaissance Aircraft flight into the system late on October 4 confirmed the existence of a closed low-level circulation , and early on October 5 the Joint Typhoon Warning Center ( JTWC ) issued its first warning on Tropical Depression Twenty-Three .