Tropical Storm Ileana (2018)

Tropical Storm Ileana was a small tropical cyclone that affected western Mexico in early August 2018,[1] causing multiple deaths and 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 July 26 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 August 4. 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 August 6, Ileana began to develop an eyewall structure as it reached its peak intensity with winds of 65 mph (100 km/h) and a pressure of 998 mbar (29.47 inHg). 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 August 7.

Tropical Storm Ileana
Tropical Storm (SSHWS/NWS)
Tropical Storm Ileana near peak intensity off the western coast of Mexico on August 5
FormedAugust 4, 2018
DissipatedAugust 7, 2018
Highest winds1-minute sustained: 65 mph (100 km/h)
Lowest pressure998 mbar (hPa); 29.47 inHg
Fatalities8 total
Damage≥ $737,000 (2018 USD)
Areas affectedwestern Mexico
Part of the 2018 Pacific hurricane season

Ileana prompted the issuance of multiple watches and warnings along the coast of Baja California Sur and western Mexico. The system paralleled the coast of Mexico 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 Mexican states of Oaxaca, Guerrero, and Mexico.

Meteorological history
Map plotting the track and the intensity of the storm, 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 July 26. The wave had virtually no convection as it crossed over the Atlantic. Once the wave entered the Eastern Pacific Ocean early on August 4, 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 17:00 UTC on August 4.[3] Only an hour later, at 18:00 UTC, the system was designated as a tropical depression while located about 230 mi (370 km) 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 August 5 at 12:00 UTC.[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 August 6 at 12:00 UTC with maximum sustained winds of 65 mph (100 km/h) and a minimum central pressure of 998 mbar (29.47 inHg), while located approximately 115 mi (185 km) 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 21:00 UTC 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 12:00 UTC on August 7, just west of Cabo Corrientes.[1]

Preparations and impact

As a precautionary measure, the Government of Mexico issued a tropical storm watch for the coast of Mexico from Lazaro Cardenas to Cabo Corrientes on August 5 at 22:40 UTC. The watch was upgraded to a tropical storm warning at 03:00 UTC on August 6. Six hours later, the Government of Mexico issued a hurricane watch for Punta San Telmo to Playa Perula and a tropical storm watch for the southern tip of Baja California Sur from Los Barilles to Todo Santos. All watches and warnings were gradually discontinued after Ileana's strongest winds were forecast to remain offshore.[1][10] Overall, a green alert was issued for Mexico, signifying a low level of danger.[13] Heavy rainfall in association with Ileana prompted the issuance of orange alerts in Álvaro Obregón and Magdalena Contreras as well as yellow alerts for the rest of Mexico City.[14][15]

In the Mexican state of Guerrero, Ileana caused a total of four deaths. On August 5, 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 3.54 in (90 mm) was recorded at the Acapulco International Airport.[18] A peak rainfall total of 7.71 in (196 mm) was observed in Jacatepec, Oaxaca.[15] In the municipality of Coyuca de Benítez, at least 20 homes were inundated and numerous streets were flooded.[19] Rip currents along the coast of Chilpancingo 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 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] In Jiquipilas, Chiapas, Ileana caused another four deaths on August 6. 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$13.6 million (US$737,000) to repair damage to roads and houses in 15 neighborhoods.[22]

In the state of Mexico, heavy rains from Ileana caused severe flooding. The Anillo Periférico, Mexico-Toluca highway, and several other roads in Mexico City experienced flooding. The Mexico City Metro (STC) also implemented safety measures for several of its lines,[23][24] such as the manual operation of trains and decrease in travel speed.[25] The San Jerónimo Canal overflowed in the El Rosal neighborhood in Magdalena Contreras. A tree measuring 15 m (49 ft) in height completely blocked a road and a total of 33 structures were inundated throughout Mexico City. In the municipality of Huixquilucan, two homes were flooded and a sewage canal overflowed.[14]

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See also
  • Other tropical cyclones named Ileana
  • Tropical Storm Irwin (1993) – a tropical storm of a similar intensity that was also absorbed by a nearby hurricane

References
  1. Avila, Lixion (9 November 2018). Tropical Storm Ileana (EP112018) (PDF) (Report). National Hurricane Center. Archived (PDF) from the original on 29 March 2019. Retrieved 28 November 2018.
  2. Blake, Eric (3 August 2018). Tropical Weather Outlook [14:46 UTC, Fri Aug 03, 2018] (Report). NHC Graphical Outlook Archive. National Hurricane Center. Archived from the original on 6 August 2018. Retrieved 18 March 2020.
  3. Blake, Eric (4 August 2018). Tropical Weather Outlook [15:53 UTC, Sat Aug 04, 2018] (Report). NHC Graphical Outlook Archive. National Hurricane Center. Archived from the original on 30 November 2018. Retrieved 29 November 2018.
  4. Berg, Robbie (4 August 2018). Tropical Depression Eleven-E Discussion Number 1 (Report). National Hurricane Center. Archived from the original on 16 December 2018. Retrieved 16 December 2018.
  5. Brennan, Michael (5 August 2018). Tropical Depression Eleven-E Discussion Number 2 (Report). National Hurricane Center. Archived from the original on 30 November 2018. Retrieved 29 November 2018.
  6. Pasch, Richard (5 August 2018). Tropical Storm Ileana Advisory Number 5 (Report). National Hurricane Center. Archived from the original on 5 August 2018. Retrieved 29 November 2018.
  7. Pasch, Richard (5 August 2018). Tropical Storm Ileana Discussion Number 5 (Report). National Hurricane Center. Archived from the original on 16 December 2018. Retrieved 16 December 2018.
  8. Berg, Robbie (6 August 2018). Tropical Storm Ileana Discussion Number 6 (Report). National Hurricane Center. Archived from the original on 16 December 2018. Retrieved 29 November 2018.
  9. Stewart, Stacy (6 August 2018). Tropical Storm Ileana Discussion Number 7 (Report). National Hurricane Center. Archived from the original on 16 December 2018. Retrieved 29 November 2018.
  10. Pasch, Richard (6 August 2018). Tropical Storm Ileana Discussion Number 8 (Report). National Hurricane Center. Archived from the original on 16 December 2018. Retrieved 16 December 2018.
  11. Pasch, Richard (6 August 2018). Tropical Storm Ileana Discussion Number 9 (Report). National Hurricane Center. Archived from the original on 16 December 2018. Retrieved 29 November 2018.
  12. Tropical Storm "Ileana" with a trend in orbiting John (Report). Tropical Cyclone Warning in the Pacific Ocean (in Spanish). Gobierno de México. 6 August 2018. Archived from the original on 13 April 2020. Retrieved 19 March 2020.
  13. Overall Green alert Tropical Cyclone for ILEANA-18 (Report). Global Disaster Alert and Coordination System. 4 August 2018. Archived from the original on 13 April 2020. Retrieved 18 March 2020.
  14. Mávil, Elizabeth (6 August 2018). "Lluvia provoca encharcamientos en nueve delegaciones de CDMX". Televisa News (in Spanish). Archived from the original on 30 December 2018. Retrieved 15 December 2018.
  15. "Precipitación acumulada (mm) del 5 al 6 de agosto de 2018 por la tormenta tropical Ileana" (Map). gob.mx (in Spanish). Conagua. Retrieved 12 March 2019.
  16. Cervantes, Juan (6 August 2018). "Arrecian efectos de la tormenta "Ileana" en Guerrero". El Universal (in Spanish). Archived from the original on 28 October 2018. Retrieved 7 August 2018.
  17. "Hallan cadáveres de dos niños en laguna de Acapulco". Sipse (in Spanish). 6 August 2018. Archived from the original on 1 April 2019. Retrieved 15 December 2018.
  18. "Tormenta Ileana deja apagones a su paso por Acapulco". UnoTV (in Spanish). 6 August 2018. Archived from the original on 15 December 2018. Retrieved 15 December 2018.
  19. "Tormenta tropical "Ileana" deja cuatro muertos en Guerrero". Diario de Yucatán (in Spanish). 7 August 2018. Archived from the original on 1 April 2019. Retrieved 15 December 2018.
  20. Olivera, Alondra (7 August 2018). "Tormenta "IIeana" provoca deslizamiento y sepulta vivienda en Oaxaca". La Silla Rota (in Spanish). Archived from the original on 1 April 2019. Retrieved 15 December 2018.
  21. "Tormenta 'Ileana' y huracán 'John' causan 7 muertes". Excélsior (in Spanish). Huffington Post. 7 August 2018. Archived from the original on 8 May 2019. Retrieved 25 October 2018.
  22. Alfaro, Fatima Paz (7 August 2018). "Sin daños por paso de huracanes Ileana y John en Michoacán". Capital Michoacán (in Spanish). Archived from the original on 23 October 2018. Retrieved 25 October 2018.
  23. "Se activa alerta amarilla por lluvias en varias delegaciones de la CDMX". Regeneracion (in Spanish). 5 August 2018. Archived from the original on 2 April 2019. Retrieved 15 December 2018.
  24. "Lluvias dejan inundaciones en la capital". La Silla Rota (in Spanish). 5 August 2018. Archived from the original on 15 December 2018. Retrieved 15 December 2018.
  25. "¿Qué es y cómo funciona la marcha de seguridad en el Metro?". Chilango (in Spanish). 14 June 2018. Archived from the original on 23 March 2020. Retrieved 23 March 2020.

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