| Category 1 hurricane (SSHS) | |
|---|---|
| Floodwaters caused by the storm | |
| Formed | September 7, 1976 |
| Dissipated | September 11, 1976 |
| Highest winds | 1-minute sustained: 80 mph (130 km/h) |
| Lowest pressure | 986 mbar (hPa; 29.12 inHg) |
| Fatalities | 10 direct, 2 indirect |
| Damage | $160 million (1976 USD) |
| Areas affected | Baja California Peninsula, southern California, southwestern Arizona |
| Part of the 1976 Pacific hurricane season | |
Hurricane Kathleen was a tropical that caused destructive impacts in California. On September 7, a tropical depression formed. Twelve hours later it was upgraded to tropical storm Kathleen. On the ninth it started accelerating north towards the Baja California Peninsula. It brushed the Pacific coast of the peninsula as a hurricane on the September 9 and made landfall as a fast-moving tropical storm on the 10th. With its circulation intact and still a tropical storm, Kathleen headed north into the United State 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. Due to flooding caused catastrophic destruction to Ocotillo, California, six people drowned in that city. Overall, the damage total was $160 million (1976 USD) and 12 deaths were blamed on the storm.
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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.[1] However, during early autumn, tropical cyclones generally form closer to the Mexican shoreline than average, making them more likely to recurve 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. These pronounced troughs thus produce a synoptic-scale flow that is conducive to steering hurricanes towards the southwestern United States.[2] However, many hurricanes that approach the southwestern United States tend to be undergoing extratropical transition as they encounter increased wind shear and as they interact with the deep troughs that caused them to recurve.[1] 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.[3]
A large area of thunderstorms, with a diameter of about 500 mi (800 km), formed 270 mi (430 km) southwest of Acapulco. Moving rapidly west-northwest, a tropical depression formed on September 7. While moving a little towards the south, the depression intensified into Tropical Storm Kathleen. Moving above 83 °F (28 °C) sea surface temperatures, Kathleen quickly strengthened. Before passing 40 mi (64 km) 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 55 mi (89 km) north of the island. Shortly thereafter, Kathleen turned north-northeast into warmer waters. [4]
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 986 mb (986 hPa). 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 700 mi (1,100 km) north of the tropical cyclone's atmospheric circulation, Kathleen's motion accelerated to speeds of 35 mph (56 km/h)-38 mph (61 km/h).[4]
After crossing the Piont Enegia Peninsula later on the morning of September 10, Kathleen made its second landfall 120 mi (190 km) north of Ensenada at 1130 UTC the same day. Unlike most tropical cyclones, Kathleen weakened only slowly over California. Tropical Storm Kathleen weakened into a depression over southern California and shortly thereafter, moved across Death Valley. On September 11, Kathleen entered western Nevada, and quickly passed west of Beatty. Finally, the center became difficult to locate,[4] and the depression dissipated later on September 11.[5] After undergoing a Fujiwhara-like interaction, where two circulation interact with each other, with a low-pressure area stalled off the Pacific coast, moisture later spread into the northwestern part of the country. After the stalled low was pulled inland, Kathleen combined with the low to produce additional rainfall over parts of California.[4]
The bulk of the rainfall from the tropical cyclone fell over Baja California Norte and Baja California Sur, to the east of its track. The highest amount reported was 6.52 in (166 mm) in San Antonio.[6]
On September 10-11, gale-force winds caused considerable damage to the city of Yuma. For a time, the sustained winds exceeded 50 mph (80 km/h), with gusts up to 76 mph (122 km/h).[7] The National Weather Service's forecast office in Tucson estimates that tropical storm-force winds extended as far east as Pima County, and as far north as Lake Havasu.[8] Rains caused severe flash-flooding in Mohave County. One man was killed when the wind blew a palm tree onto his mobile home[7] and 13 people across the state were hurt.[9] The Tucson metropolitan area was particularly hard hit with flash flooding, with golf-boll size hail. On Mount Lemmon, the hail reached a depth of 5 in (13 cm).[7] While most of the rainfall from Tropical Storm Kathleen fell in California,[6] 2.87 inches (7.3 cm) fell at the Davis Dam on the Colorado River.[10]
The state received record rainfall, with 14.76 in (37.5 cm) falling on the southern slopes of Mount San Gorgonio, and 10.13 in (25.7 cm) accumulated on Mount Laguna.[11] Because the village is situated atop an alluvial fan[12] a 40 ft (12 m) wall of water exited a mountain canyon. Ocotllio was flooded with 4 feet (1.2 m)-6 ft (1.8 m) of water[11];subsequently, half the town was destroyed.[13] Six people drowned in the mud and waters in the town[11] and two people were initially reported missing, though they were later found by officials.[9] Overall, Ocotllio was 70%-80% destroyed. Officials evacuated 175 people from the flooded area of Ocotllio and the nearby communities that surround the Salton Sea. The sea itself rose 6 in (150 mm)-8 in (200 mm).[4] A quarter mile of interstate and a 60-foot bridge were destroyed by the flood, which also washed away mobile homes, trucks, and cars.[9]
In Los Angeles, two people died of injuries suffered from slippery-roads. One man drowned in El Centro.[9] and two people drowned when their cares tumbled into the water near the city.[13] Record flood stage was attained at numerous streams near the Coachella Valley. Widespread property damage was recorded on the eastern slopes of the Sierra Nevada as well as the nearby desert.[11] Across the San Joqin Valley, 2/3 of the $150 million rasin crop were threatened. Crops including cotton, lettuce, and hay were damaged.[13]
Homeowners in Palm Desert suffered $4 million in damage from the storm.[13] Many flood control structures throughout the area failed to work[14] because the town received more than a years worth of rainfall in a matter of days.[13] The control structures in the area were rebuilt, and they withstood Hurricane Doreen during the 1977 Pacific hurricane season.[15] No serious injuries were reported throughout the desert city, though two agricultural dikes broke.[13]
Several miles of railway track,[4] three trestles that belonged to the San Diego and Arizona Eastern Railway were destroyed, and five others were damaged. At more than 50 other locations, tracks were buried by mudslides or had the ground under them washed away. After assessing the damage from Kathleen, the Southern Pacific Transportation Company decided in 1977 to abandon most of the railroad.[16] A 700 ft (210 m) section of Interstate 8 from Yuma to San Diego was destroyed.[4]
Overall, hundreds of homes were damaged or destroyed;[13] Tropical Storm Kathleen was described as a one and 160 year event.[11] Total damage was $160 million, making Kathleen one of the costliest tropical storms in state history.[17]
Parts of California were declared a disaster area[18] and flash flood watches were issued throughout Southern California, including the desert and mountains.[19] Flash flood warnings were also issued for parts of the state, as well as nearby states Nevada and Arizona, but were dropped as the rain tampered off on September 11.[13]
In Wyoming, the cyclone is credited for the first known sighting of a White Ibis in the state's history.[20] In Montana, Kathleen dropped locally heavy rainfall approaching 2 inches (51 mm) in localized spots[10] enough to become the wettest known tropical cyclone in state history.[21]
