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What happened, where and when?
On 7 November 2024, the National Meteorological Institute (IMN) issued a Meteorological Advisory reporting that, following the indirect influence of Hurricane Rafael, the Intertropical Convergence Zone persisted over the Central American Isthmus. This phenomenon, combined with the passage of Tropical Wave #45, exacerbated soil saturation across various regions of the country, reaching critical levels in both Peninsulas, the North Pacific, South Pacific mountains, Northern Zone, Central Pacific, and Central Valley. Due to the elevated saturation levels, these areas faced significant vulnerability to potential incidents, prompting the IMN to recommend heightened preventive measures (1).
Subsequently, on 9 November 2024, the National Emergency Commission (CNE) issued Alert Notice 43-24, declaring an Orange Alert for the Northern Zone and Northern Caribbean, while maintaining the same alert level for the South Pacific, Central Pacific, North Pacific, and Central Valley. Meanwhile, the Southern Caribbean region was placed under a Yellow Alert, emphasizing the need for preventive measures in these areas due to the risk of landslides and flooding caused by high soil saturation levels (2).
On 12 November 2024, the CNE declared a Red Alert (maximum level) for the provinces of Guanacaste and Puntarenas, both located along the Pacific coast. An Orange Alert (high level) was maintained for the rest of the country, except for the Limón province in the Caribbean, which remained under a Yellow Alert (intermediate level). The CNE announced that the rainfall pattern was expected to persist throughout the week and that the IMN was closely monitoring Tropical Wave #46, which had a high potential to develop into a tropical cyclone over the Caribbean Sea within the next seven days (3).
Furthermore, on 13 November 2024, Meteorological Report No. 20 confirmed that Tropical Wave #46 was intensifying into a low-pressure system and becoming Potential Tropical Cyclone #19 (PTC#19). By late afternoon, the center of this system was located over the Caribbean Sea, approximately 814 km northeast of Limón. According to the National Hurricane Center (NHC) projections, PTC#19 was expected to reach tropical storm status by the morning of Thursday, November 14, and its trajectory was projected westward toward Honduras. PTC#19 would promote a moisture flow toward Costa Rica, combined with the Intertropical Convergence Zone, maintaining unstable weather conditions across the country. It was also confirmed that high soil saturation levels persisted in much of the country, ranging between 85% and 100% (4).
On 14 November 2024, Meteorological Report No. 23 stated that Tropical Depression #19 (TD#19) reached tropical storm status around midday, being named Sara, with sustained winds of 65 km/h. At that time, Sara was located 105 km north-northwest of Cabo Gracias a Dios and was expected to continue moving westward, remaining off the coast of Honduras. This tropical cyclone's position caused indirect influence over Costa Rica, with consistent moisture flow from the Pacific Ocean entering the country.
Rainfall remained persistent across various regions of the country. Over the past six hours, maximum precipitation levels were recorded in Paquera (60 mm), Orosi Volcano (88 mm), La Cruz (69 mm), Ciudad Neily (55 mm), Santa Bárbara (30 mm), Laguna Fraijanes (38 mm), Cariari de Limón (35 mm), and Cutris de San Carlos (33 mm), among others.
During the night of Thursday and into the early hours of Friday, 15 November, rainfall activity was expected to intensify in the Pacific regions, with variable intensity rains and a likelihood of heavy downpours. The Central Valley was forecasted to experience intermittent rains, with greater intensity in the western sector. The rest of the country was projected to have variable cloud cover and occasional rains in mountainous areas and coastal zones of the Caribbean.
The rainfall pattern associated with this tropical cyclone's indirect influence was expected to persist from Thursday to Saturday in southern regions of the country and from Thursday to Sunday in the rest of the Pacific slope and parts of the Central Valley.
High soil saturation levels persisted across much of the country, with saturation indices between 85% and 100%. Consequently, there was a high probability of flooding in vulnerable areas, particularly in the Pacific regions, and landslides in the mountains of the Pacific, western and eastern Central Valley, Northern Zone, and the Tilarán and Caribbean mountain ranges (5).
Initially, during the early stages of the emergency, the CNE projected that approximately 1,500 families, or about 7,500 people, would be affected. This preliminary estimate was based on a quick assessment of the potentially impacted areas, as at that time, precise and detailed information on the extent of the damage was not yet available.
Subsequently, as data was consolidated and more detailed assessments became available, the estimate was updated. It was determined that 1,098,668 people were directly or indirectly affected, mainly due to issues related to damage to essential infrastructure such as water, electricity, and communications. This larger figure comes from an internal report prepared by the CNE and shared with the National Society, which was based on a more comprehensive analysis of the impacts recorded in the affected areas.