[1] The next day, the National Hurricane Center (NHC) noted an associated area of showers and thunderstorms, indicating that gradual development was possible.

[2] The system had become better organized and on July 25,[3] the NHC continued to remark upon the potential for the weak low pressure area—accompanied by disorganized convective activity—to develop.

[4] On July 26, the system became better-organized, and under favorable conditions it was upgraded to a tropical depression at 1200 UTC, while located about 760 miles (1,220 km) to the south-southwest of Cabo San Lucas, Mexico.

[10] Increasingly colder waters and growing wind shear continued to affect Darby, and the cyclone weakened to a tropical storm on July 30.

Darby soon crossed into the Central Pacific Hurricane Center's area of responsibility, and it dissipated as a tropical cyclone on August 1.

However, its remnants continued westward under the low-level trade winds, and dropped heavy rainfall on Hawaii several days after the cyclone dissipated.

[1] Upon reaching the Hawaiian Islands, the remnants of Darby contributed to heavy rainfall and high winds,[1] prompting the issuance of flash flood watch.

[13] Along the eastern shores of Kauai, Oahu, Molokai, Maui, and the Island of Hawaii, the system generated 4 to 8 feet (1.2 to 2.4 m) swells.

[20] Excessive runoff around Kailua-Kona resulted in extensive flooding that forced the closure of five schools, submerged several roads, and triggered rockslides.