Diagnosis: Tropical wave #18 is over Costa Rica this Thursday, causing unstable conditions in the maritime sector off the coast of Limón, which is causing rain and showers with thunderstorms on the coast and surrounding plains. In addition, deep convection events are being generated in the North Zone with showers between Puerto Viejo de Sarapiquí and La Fortuna. At the moment, the accumulated amounts are around 30 mm in the last two hours.

Forecast: For the rest of the morning, cloudiness and rain/showers with thunderstorms will continue in the Caribbean and North Zone, amounts between 20-45 mm are estimated. Possible showers/drizzles in the Central Volcanic Mountain Range and surrounding areas. In the afternoon, variable rainfall is expected in the Central Valley, again the strongest in the North and West, estimated accumulated amounts between 20 mm and 50 mm in 6-hour periods. For Guanacaste, the Northern Zone and the mountains of the Caribbean, heavy rains and downpours with thunderstorms are expected, amounts between 40 mm and 75 mm in periods of 6 hours. In the Central and South Pacific, there will be isolated downpours, extending towards coastal areas, estimated accumulations between 10 mm and 40 mm, with possible higher amounts in a scattered manner. During the course of the night, the downpours with thunderstorms could be reinforced again in the Caribbean, the Northern Zone and coastal parts of the South Pacific.

The tropical wave will be leaving the country this afternoon, however, its interaction with surrounding systems such as the Intertropical Convergence Zone, moderate to strong trade winds in the Caribbean Sea and transitory atmospheric oscillations, could maintain instability in the Costa Rican Caribbean this Friday and Saturday.

Warning: The rains projected for urban areas may again be precursors to flooding and sewer saturation in already recurring areas. Saturated soils are recorded in the mountains of the South Pacific, Valle del General, Golfito, Osa, the entire Northern Zone, Guanacaste and the mountains of the Northern Caribbean, which is why these are regions vulnerable to landslides and possible floods. Due to the above, the IMN recommends: • Caution due to sewer saturation in places prone to this type of flooding. • Prevention in the event of an electrical storm and seeking shelter in a safe place in the event of strong gusts of wind occurring or perceived near the storm clouds, due to the possible fall of tree branches, power lines, among others. These gusts can reach 80 km/h in some isolated cases.

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Gabriela Chinchilla R. Meteorologist DMSA-IMN