While passing through the Papahānaumokuākea Marine National Monument, Neki was downgraded to a tropical storm after the center became exposed from the deepest convection.

The origins of Hurricane Neki were from a surface trough that persisted near the equator in the central Pacific Ocean in the middle of October 2009.

A weak tropical disturbance became evident in the trough on October 15, and three days later the system began developing curved bands of convection on its northern and southern periphery.

Following the formation of a well-defined circulation, it is estimated the system developed into Tropical Depression Three-C late on October 18, about 730 mi (1175 km) south of Ka Lae, Hawaii.

[1] After reaching hurricane status, Neki began rapidly intensifying as it turned northward, due to an approaching upper-level trough to its north.

[6] Early on October 22, Neki reached its peak winds of 125 mph (205 km/h) about 215 mi (345 km) northeast of Johnston Atoll, based on estimates from satellite imagery using the Dvorak technique.

Afterward, the trough that influenced the hurricane's track also began restricting westerly outflow and increasing wind shear, which caused a steady weakening trend.

[9] The storm resumed its northward motion after the ridge receded to the east, and on October 26 Neki weakened to a tropical depression once the circulation decoupled from the thunderstorms.

[11] Later that day, a hurricane watch was issued for the Papahānaumokuākea Marine National Monument for areas between the French Frigate Shoals and Lisianski Island.

[17] As the hurricane turned northward and was seen as a threat to the Hawaiian Islands, officials in the Papahanaumokuakea requested that all 17 personnel in the region be evacuated.