Tropical Wave No. 48 is expected to cross Costa Rica today bringing a greater chance of afternoon downpours and thunderstorms as already wet areas face an increased risk of flooding and landslides. The National Meteorological Institute (IMN) said a drop in atmospheric pressure across Central America is pulling the Intertropical Convergence Zone (the band near the equator where trade winds meet, creating clouds, storms and frequent heavy rain) closer to Costa Rica.
Combined with the tropical wave, that will increase atmospheric instability over the country and help fuel rainfall through Thursday and into the coming days. The day is expected to begin relatively calm and much of Costa Rica will see partly cloudy skies and warm, muggy conditions during the morning before the weather changes during the afternoon.
The IMN expects showers and thunderstorms to develop first around the mountains and higher elevations. Rain could then spread into lower parts of the Greater Metropolitan Area (GMA), the Northern areas and the Caribbean. In the Central Valley, San José, Alajuela, Cartago and Heredia are forecast to remain partly cloudy during the morning before scattered afternoon downpours and thunderstorms develop.
Cloudy conditions, isolated rain and patches of fog could linger into Thursday night. San José is expected to reach about 28°C (83°F), while Alajuela could climb to 31°C (88°F). Cartago will be cooler at around 25°C (77°F), with Heredia near 29°C (84°F). The North Pacific will also see a hot morning followed by scattered thunderstorms during the afternoon. Liberia could reach around 36°C (96°F), while Puntarenas is also forecast near 36°C. Nicoya could reach approximately 35°C (94°F).
In the Central and South Pacific, rainfall is expected mainly around mountainous areas during the afternoon, with variable cloud cover continuing into the evening. Quepos is forecast to reach about 33°C (91°F), while Golfito could reach 34°C (93°F). The Northern Zone and Caribbean could also see afternoon thunderstorms, particularly near the mountains, followed by scattered rain into the evening. Ciudad Quesada is forecast near 28°C (82°F), while Limón could reach around 30°C (85°F). Of particular concern are areas where the ground is already saturated after recent rainfall.
In its latest weather advisor from yesterday, the IMN reported soil saturation above 95% in parts of the Northern Zone and Northern Caribbean, as well as areas near the mountains of the Central and South Pacific. The institute warned that additional rainfall could increase the possibility of overflowing streams, drainage problems, localized flooding and landslides.
The IMN also said rainfall totals in some of the more affected areas could reach 20 to 50 millimeters, with localized totals of 60 to 80 millimeters. In other parts of the Central Valley, rainfall totals of 5 to 30 millimeters were possible. Anyone in that part of Costa Rica should use extra caution in areas prone to flooding and landslides, particularly during the afternoon and evening. The IMN also recommends seeking shelter during thunderstorms and remaining alert for strong wind gusts near storm cells.
The wetter pattern may continue beyond today. The IMN’s weekly outlook through October 4 calls for humid and unstable conditions, with the Central Pacific and mountainous parts of the Caribbean and Northern Zone carrying some of the greatest potential for moderate to heavy rain.
