Ileana (2018)

A small tropical cyclone formed quickly from a tropical wave after it crossed Central America and reached the eastern Pacific. It became a tropical depression on 4 August 2018 in the Gulf of Tehuantepec about 200 nautical miles south‑southeast of Puerto Ángel, Mexico, strengthened to Tropical Storm Ileana on 5 August, moved west‑northwest very near the southwest coast of Mexico, peaked on 6 August, and was absorbed and dissipated by 7 August just west of Cabo Corrientes as it merged into outer bands of nearby Hurricane John.

Ileana did not make a classic separate series of landfalls; instead it stayed close to the Mexican coast and was disrupted by land interaction with the Sierra Madre and by the larger Hurricane John. No distinct NHC landfall entries for Ileana are listed in the best track; the system dissipated near the coast of Jalisco (west of Cabo Corrientes) late on 6 to early 7 August.

The storm’s maximum intensity was 55 kt (63 mph) with a minimum central pressure of 998 mb at 1200 UTC 6 August 2018, corresponding to a moderate tropical storm (below hurricane strength).

Storm surge and rainfall impacts were localized. Radar and coastal observations showed coastal flooding and high waves along Guerrero’s Pacific coast; numerous houses were flooded in the Costa Grande area of Guerrero. Newspapers and local reports cited high waves that swept a person off a beach. Exact storm-surge heights were not detailed in the NHC report; heavy rains produced significant river flooding in places such as Chilpancingo, Guerrero, where rivers overtopped or flowed strongly enough to cause drownings.

There were four reported deaths in Mexico attributed to Ileana: three people drowned in flooded rivers in Chilpancingo, Guerrero, and one person drowned after being swept off a beach by high waves. The most notable impacts were flooding of homes and dangerous surf along the southwest coast of Mexico, particularly in Guerrero.

Ileana was notable for how rapidly it formed so close to the coast and for being unusually small. Its genesis was not well anticipated in NHC outlooks until about 30 hours or less before formation, and forecasts had larger-than-average errors for this system: track and intensity forecasts struggled to capture the timing of Ileana’s quick intensification late on 5 August and its early weakening and absorption by Hurricane John.