Hurricane Kathleen was a Category 1 Pacific hurricane that had a destructive impact in California. On September 7, 1976, a tropical depression formed; two days later it accelerated north towards the Baja California Peninsula. Kathleen brushed the Pacific coast of the peninsula as a hurricane on September 9 and made landfall as a fast-moving tropical storm the next day. With its circulation intact and still a tropical storm, Kathleen headed north into the United States and affected California and Arizona. Kathleen finally dissipated late on September 11.
Damage in the United States was considerable. California received record rainfall, with over a foot of rain falling in some areas. Flooding caused catastrophic destruction to Ocotillo, and six people drowned. Flooding extended west; railway tracks were destroyed in Palm Desert and high winds and severe flooding were recorded in Arizona. Overall, the damage total was $160 million (1976 USD, about $760 million in 2023) and 12 deaths were attributed to the storm.
Background
Tropical cyclones do not typically bring high winds to the southwestern United States. Most Pacific hurricanes are embedded in easterly winds south of the subtropical ridge, and thus move westward—away from large land masses—until they dissipate over cold waters. However, during early autumn, tropical cyclones generally form closer to the Mexican shoreline than average, making them more likely to recurve, or to curve again, northwards under the influence of an approaching trough. These troughs tend to extend farther to the south during the latter part of the Pacific hurricane season, in the period between late August and early October. They also produce a synoptic-scale flow that is conducive to steering hurricanes towards the southwestern United States. However, many hurricanes that approach the southwestern United States tend to be undergoing extratropical transition as they encounter increased wind shear and markedly cooler sea surface temperatures, and as they interact with the deep troughs that caused them to recurve. Kathleen is one of only six recorded tropical cyclones in the eastern Pacific Ocean known to have brought gale-force or hurricane-force winds to the Continental United States.
Meteorological history
A large area of thunderstorms, with a diameter of about , formed southwest of Acapulco. Moving rapidly west-northwest, a tropical depression formed on September 7. While briefly moving towards the east, the depression intensified into Tropical Storm Kathleen. Moving above sea surface temperatures, Kathleen quickly strengthened. Before passing east of Socorro Island, Kathleen reached its secondary peak with winds of 65 mph (115 km/h). Kathleen then weakened considerably, and by 0600 UTC September 9, Tropical Storm Kathleen was barely a tropical storm. At this time, the system was located at north of the island. Shortly thereafter, Kathleen turned north-northeast into warmer waters.
Subsequently, the tropical storm began to re-strengthen. Despite moving rapidly north, the cyclone strengthened into Hurricane Kathleen. The hurricane passed near several ships, and was intercepted by a Hurricane Hunter aircraft early on September 10. It is estimated that the storm peaked in intensity around that time, with winds of 80 mph (130 km/h) and a barometric pressure of . However, Kathleen never developed an eye. About an hour after the first flight reached Kathleen, a second flight suggested that Kathleen had weakened back into a tropical storm. With precipitation falling in the United States, some north of the cyclone's atmospheric circulation, Kathleen's motion accelerated to speeds of -.
After crossing the Point Eugenia peninsula (the cyclone's first landfall) later on the morning of September 10, Kathleen made its second landfall south of Ensenada at 1130 UTC the same day. Unlike most tropical cyclones, Kathleen weakened slowly over California. Tropical Storm Kathleen weakened further into a depression over southern California and shortly thereafter, moved across Death Valley. On September 11, Kathleen entered western Nevada. Finally, the center became difficult to locate, and the depression dissipated later on September 11. After undergoing a Fujiwhara-like interaction, where two circulations interact with each other, with a low-pressure area stalled off the Pacific coast, moisture later spread into the northwestern part of the United States. After the stalled low was pulled inland, Kathleen combined with the low to produce additional rainfall over parts of California.