Tropical Storm Ileana was a small tropical cyclone that affected western Mexico in early August 2018,[1] causing deadly flooding. The eleventh tropical cyclone and ninth named storm of the 2018 Pacific hurricane season,Ileana originated from a tropical wave that the National Hurricane Center began monitoring on July26 as the wave left the west coast of Africa. The wave traveled across the Atlantic Ocean with no thunderstorm activity,before crossing into the Eastern Pacific Ocean early on August4. Rapidly developing,the disturbance organized into a tropical depression on the evening of the same day. Initially,the depression was well-defined,but it soon degraded due to northerly wind shear. Despite the unfavorable conditions,the system began to strengthen on August 5,becoming Tropical Storm Ileana. A day later,on August6,Ileana began to develop an eyewall structure as it reached its peak intensity with winds of 65mph (100km/h) and a pressure of 998mbar (29.47inHg). The storm gradually became intertwined with the nearby Hurricane John;over the next day,the circulation of John disrupted Ileana before ultimately absorbing it on August7.
Ileana prompted the issuance of multiple watches and warnings along the coast of Baja California Sur and the Pacific coast of Mexico. The system paralleled the Pacific coast for much of its existence. Ileana caused a total of eight deaths in Mexico;four people were killed in Guerrero and another four died in Chiapas. Flooding also ensued in the states of Oaxaca,Guerrero,and Mexico.
Meteorological history
Map plotting the storm's track and intensity,according to the Saffir–Simpson scale
The origins of Ileana can be traced back to a tropical wave that departed from the west coast of Africa on July26. The wave had virtually no convection as it crossed over the Atlantic. Once the wave entered the Eastern Pacific Ocean early on August4, thunderstorm and convective activity rapidly increased.[1] The National Hurricane Center (NHC) first noted the potential for development on August 3.[2] After satellite imagery indicated that an area of low pressure had formed a few hundred miles south of the Gulf of Tehuantepec and was showing signs of organization, the NHC raised the system's two-day development chances to 50% around 17:00UTC on August 4.[3] Only an hour later, at 18:00UTC, the system was designated as a tropical depression while located about 230mi (370km) south-southeast of Puerto Angel, Mexico.[1] Around that time, the depression had a well-defined low-pressure center and a pronounced, arced band of deep convection.[4] Six hours later, the structure of the depression had degraded due to northerly wind shear caused by the stronger disturbance that would later become Hurricane John. The low-level center of the depression had become exposed in the northwest as it moved out from under the edge of the convection; simultaneously, convection decreased in the east and south. The depression was traveling west-northwest under the influence of the aforementioned disturbance, which was located to the west, and a mid-level ridge located to the east.[1][5] Despite the disruptive wind shear, the depression then began to strengthen, becoming Tropical Storm Ileana on August5 at 12:00UTC.[1][6] At that time, Ileana had a fairly symmetrical structure and a central dense overcast-like feature.[7]
Ileana continued to strengthen over the next day after entering an area with warm sea surface temperatures of 86 to 88°F (30 to 31°C).[8] Ileana reached peak intensity on August6 at 12:00UTC with maximum sustained winds of 65mph (100km/h) and a minimum central pressure of 998mbar (29.47inHg), while located approximately 115mi (185km) southwest of Acapulco.[1] Around the same time, Ileana had strong deep convection with cloud temperatures of −121 to −130°F (−85 to −90°C).[9] Soon after, microwave imagery and Acapulco radar showed the emergence of an eyewall structure at the mid-levels of the system.[10] By 21:00UTC on August 6, Ileana had become increasingly intertwined in the outer bands of Hurricane John to the west as the two systems began to experience the Fujiwhara effect.[11][12] The nearby Sierra Madre Mountains further disrupted Ileana's circulation center. The storm was completely absorbed by John at 12:00UTC on August7, just west of Cabo Corrientes.[1]
In the state of Guerrero, Ileana caused a total of four deaths. On August5, the body of 35-year-old man was discovered in the Huacapa River in Chilpancingo. The man had reportedly been pushing a car out of a ravine when a strong current pulled him down to the river where he drowned. A fishing boat capsized in Acapulco, causing an 8-year-old and a 15-year-old to fall into the Laguna and drown.[16][17] The storm caused power outages in multiple Acapulcan neighborhoods and left flooding there. A rainfall total of 3.54in (90mm) was recorded at the Acapulco International Airport.[18]Rip currents along the coast at Acapulco resulted in the death of a tourist at La Condesa beach. He was rescued by lifeguards, but later died despite receiving medical treatment.[16] In the nearby municipality of Coyuca de Benítez, at least 20 homes were inundated and numerous streets were flooded.[19] In the municipality of Santiago Choapam in Oaxaca, heavy rains from Ileana caused a landslide that left a house in ruins. All inhabitants of the structure were unharmed.[20] A peak rainfall total of 7.71in (196mm) was observed in Jacatepec, Oaxaca.[15] In Jiquipilas, Chiapas, Ileana caused another four deaths on August6. A vehicle containing 18 individuals was swept away by water currents while attempting to cross a flooded bridge; three children and one adult were later found dead.[21] The state of Michoacán required MX$13.6million (US$737,000) to repair damage to roads and houses in 15 neighborhoods.[22]
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