Dolores (2015)

A tropical disturbance that moved off Central America became a tropical depression on July 11, 2015, about 300 nautical miles south-southeast of Acapulco, Mexico. It strengthened into Tropical Storm Dolores late on July 11–12 and moved west-northwestward, staying well offshore of the southwest coast of Mexico. Dolores became a hurricane on July 13, rapidly intensified to its peak on July 15, then weakened as it moved past Socorro Island and over progressively cooler water. The cyclone became a remnant low on July 18 and dissipated by July 22 a few hundred nautical miles west-southwest of San Diego, California.

Dolores did not make a mainland landfall. It passed about 15–20 nautical miles northeast of Socorro Island on July 16, where hurricane conditions were recorded. No other landfalls were reported along the Mexican coast or in the United States.

The storm’s estimated maximum sustained winds were 115 knots (about 132 mph) at 0600 UTC on July 15, with a best-track minimum central pressure of 946 mb. At its peak Dolores was a major hurricane (Category 3 on the Saffir-Simpson scale). When it passed near Socorro Island around 0000 UTC July 16 its intensity had decreased to about 95 kt (≈110 mph).

Dolores produced a recorded peak wind of 69 kt (1-minute) with gusts to 100 kt at an automated station on Socorro Island, and a minimum pressure of 968.4 mb was measured there (post-analysis suggests that value may be a couple of millibars too low). As Dolores’ remnants moved north, they brought an unusual surge of moisture into southern and central California on July 17–18. Widespread 2–3 inch totals occurred across southern California; Ramona received close to 4 inches, some mountain areas and parts of the I‑10 corridor had radar-estimated totals as high as 6–9 inches, San Diego recorded 1.03 inches (an all-time July monthly record) and Los Angeles recorded 0.28 inches (also a July record). High surf affected south-facing beaches along the southern California coast for a couple of days.

There were no U.S. impacts directly attributed to Dolores as a tropical cyclone and no storm-related deaths confirmed in the NHC report. Flooding and debris flows in Ramona damaged about 90 homes and submerged many cars; portions of Interstate 10 were washed out west of the Colorado River. A person struck by lightning in California City was not clearly linked to Dolores and is not attributed to the storm in the report.

Noteworthy items: Dolores formed in part because of an unusual upper-level trough, a relatively rare formation mechanism for eastern Pacific storms. Official NHC track forecasts performed very well (errors well below recent averages), while intensity forecasts had larger-than-average errors, in part because rapid intensification and an eyewall replacement led to unexpected short-term changes in strength.