Olaf (2015)

A tropical depression formed on 15 October 2015 from a tropical wave about 860 nautical miles south-southwest of Cabo San Lucas, Mexico. The system moved generally westward and became Tropical Storm Olaf on 17 October. Olaf underwent rapid strengthening in a warm, low-shear environment and became a hurricane on 18 October at an unusually low latitude near 9.3°N. The storm moved westward into the central Pacific, tracked northwestward, then turned north and northeast under changing steering currents before weakening and becoming post-tropical on 27 October about 1,025 n mi west-southwest of San Diego. Olaf dissipated by 28 October.

Olaf did not make any landfalls. It remained well offshore of Mexico and the Hawaiian Islands throughout its life, and no coastal watches or warnings were required.

The peak intensity of Olaf was estimated at 130 knots (150 mph) with a minimum central pressure of 938 mb, making it a strong Category 4 hurricane at its peak on 20 October. Olaf maintained that peak intensity for about 12 hours while moving from the eastern into the central Pacific.

High surf from Olaf affected the Hawaiian Islands between 21 and 26 October. Reported surf heights were 10 to 20 feet along east-facing shores of the Big Island, 8 to 12 feet along east-facing shores of Maui, and 6 to 9 feet along south-facing shores of the other islands. High surf inundated a stretch of Highway 137 on the southeast side of the Big Island with about eight inches of water on 22 October. There were no ship reports or surface observations of tropical-storm-force winds tied to Olaf, and no reported rainfall totals of notable magnitude in the NHC report.

There were no reports of damage or casualties associated with Olaf. The storm primarily remained over open water and produced only coastal surf impacts in Hawaii.

Notable aspects of Olaf include its unusual origin and path: it was the lowest-latitude hurricane on record in the eastern Pacific and the only recorded Category 4 hurricane south of 10°N. Olaf is also the only tropical cyclone on record to move from the eastern Pacific into the central Pacific and then back into the eastern Pacific. Forecasts of its genesis and track were generally successful, with official track forecasts outperforming many guidance models at several forecast times.