[2] The fourth of these was spawned by a tropical wave several hundred miles south-southeast of Acapulco, Mexico, first noted by the National Hurricane Center (NHC) on July 9.

[3][4] Amid favorable conditions, convection associated with the low developed and increased in organization,[5] and a tropical depression formed on the afternoon of July 11 centered 290 mi (470 km) south-southwest of Manzanillo, Mexico.

[2] Despite moving over sea surface temperatures of at least 82 °F (28 °C), moderate northeasterly wind shear hindered development; however, the depression soon obtained sufficient organization to be upgraded to a tropical storm and given the name Darby.

[6] On July 13, the shear decreased, and as a result Darby began to intensify quickly, strengthening into a hurricane 30 hours after becoming a tropical storm.

[8] Tracking steadily west-northwestward along the southern periphery of a subtropical ridge, Darby continued to intensify albeit at a slower rate due to its proximity to dry air.

[1][11] Darby reached its peak intensity as a Category 3 hurricane with winds of 120 mph (190 km/h) and a minimum pressure of 958 mbar (958 hPa; 28.3 inHg).

[1] Embedded in cool sinking air and moving over decreasing sea surface temperatures,[12] Darby began a gradual weakening trend, degrading to a Category 1 hurricane by July 18.

[1] Despite warming cloud tops, Darby exhibited a well-defined circulation and a ragged eye feature, remaining a minimal hurricane through the rest of the day.

[28] Eventually, after Darby made landfall in Kaʻū District in the afternoon of July 23,[19] the tropical storm warning was extended to all islands in the state of Hawaii.

[35] Both the Hawaii and Maui campuses of the Kamehameha Schools were closed over the weekend, and athletic events due to be held there were cancelled or postponed.

After passing over the Big Island, Darby proceeded northwestward via the Kauai Channel, while resulting in heavy rains over southern slope of Haleakala on Maui.

In Oahu, rainfall, sometimes at rates of 3 to 4 in (75 to 100 mm) per hour, caused flash flooding in several areas within the urban core of Honolulu and along windward slopes.