From AMS Glossary
A severe thunderstorm with vivid lightning and violent squalls coming from the land on the west coast of Nicaragua and Costa Rica in Central America.
Chubascos are especially frequent in May, with a secondary maximum in October. Soon after noon, dark, heavy clouds form over the mountains, becoming denser and lower. At about 4 p.m. the southwesterly sea breeze veers to east-northeast, and the storm breaks, usually continuing until about 8 p.m.