Genevieve (2020)

A tropical wave that moved off Central America developed into Tropical Depression Twelve about 260 nautical miles south of Puerto Ángel, Mexico, at 1200 UTC on 16 August 2020. The system became Tropical Storm Genevieve later that day and moved northwestward parallel to the Mexican coast. Genevieve rapidly intensified and reached hurricane strength on 17 August, becoming a major hurricane early on 18 August. Its peak intensity occurred around 1200 UTC 18 August, after which it weakened while turning toward the north-northwest and passed near the southern tip of the Baja California peninsula on 20 August. The cyclone became post-tropical by 1800 UTC 21 August and its remnants dissipated around 12:00 UTC 22 August just west of the central Baja peninsula.

Genevieve did not make a direct landfall as a major hurricane on the Mexican mainland, but its center passed about 45 nautical miles southwest of Cabo San Lucas around 0600 UTC 20 August, bringing near-hurricane-force winds and very heavy rain to extreme southern Baja California Sur. Tropical storm warnings and hurricane warnings were issued for portions of southern Baja California Sur in the days before the closest approach, with the hurricane warning issued only about three hours before tropical-storm-force winds began near Cabo San Lucas.

The storm’s maximum sustained winds were estimated at 115 knots (about 132 mph) at peak intensity, with an estimated minimum central pressure of 950 mb, making it briefly a Category 4 hurricane on the Saffir–Simpson scale. That peak was short-lived; weakening began about six hours later and continued as Genevieve moved over cooler water and encountered increased wind shear.

Storm surge effects were limited in the official record, but rainfall was significant in places. Cabo San Lucas reported the highest rainfall total at 11.2 inches (about 284 mm). Isolated rainfall amounts of about 4 inches were reported in parts of mainland Mexico, mainly Oaxaca and Guerrero. The highest measured sustained wind on land was 61 knots (70 mph) at the Cabo San Lucas Marina site, with a peak gust of 78 knots (90 mph).

Genevieve was responsible for six direct deaths in Mexico: four on the mainland (two killed by landslides in Oaxaca and two drowned in swollen rivers) and two surf-related drownings in the Los Cabos area of Baja California Sur. Flooding caused some damage to roads and structures in mainland Mexico, and the governor of Baja California Sur reported damage to hydraulic, highway, and electrical systems in the state. Insurer AON estimated total damages of at least $50 million (USD).

Noteworthy aspects include the storm’s rapid intensification to a Category 4 hurricane and the subsequent rapid weakening before affecting Baja California Sur. Forecasts generally predicted genesis well in advance, but official intensity forecasts had larger-than-normal errors because models did not fully capture the rapid strengthening and then the early weakening. Some numerical guidance, such as the HWFI model, handled the intensity changes better than the official forecasts.