Costa Rica’s Tropical Depression Risk Fades but the Downpours Don’t

The low-pressure system off Central America’s Pacific coast is now less likely to become a tropical depression, but that doesn’t mean a dry weekend for Costa Rica. You should still expect afternoon and evening downpours from today through Sunday, on ground that is already close to its limit. In its outlook issued late Thursday, the U.S. National Hurricane Center gave the system a 40% chance of forming over both the next 48 hours and the next seven days. That is down from the 60% seven-day chance it carried yesterday morning, when the odds of a depression had been climbing. The hurricane center said a depression could still form over the weekend while the low drifts slowly offshore. After that, stronger winds high in the atmosphere should stop it from organizing further. Either way, the center warned the system could bring areas of heavy rain to parts of Central America through the weekend. For Costa Rica, rain was always the bigger risk, not wind. A tropical depression has sustained winds below 63 km/h (39 mph). What matters more is how much water falls, and where it goes once it hits the ground. The rain is already adding up. The National Meteorological Institute (IMN) recorded up to 151 millimeters (5.9 inches) in mountain areas near the Poás Volcano, according to its Thursday 5 p.m. update. The institute said the low, tied to the Intertropical Convergence Zone, will keep clouds and showers over the country from Friday through Sunday. Here is why that matters. Soils on the Pacific slope are 80% to 90% saturated, according to IMN data. When the ground can’t soak up any more water, rain runs straight into creeks, drains and culverts. Streams rise fast, city drains back up and hillsides along roads can slide. That pattern caused flash floods in Heredia and Escazú in mid-October. On Friday, rain can start early in the morning along the North Pacific coast. In the afternoon, it spreads. The Central Valley should see scattered showers that can last into the night, with a good chance of fog. The heaviest rain is expected in the Northern Zone and on the Caribbean side, starting in the mountains and moving down into the lowlands. In the Northern Zone, IMN expects 20 to 40 mm (0.8 to 1.6 inches) in the afternoon, with local totals above 50 mm and possibly 60 mm (2 to 2.4 inches). Mountain areas of the Central Pacific could get 15 to 30 mm (0.6 to 1.2 inches). Storms can also bring isolated gusts of up to 80 km/h (50 mph), strong enough to knock down branches and power lines. It will feel cooler, too. IMN forecast a high of 25.8 C (78 F) and a low of 18.8 C (66 F) in San José on Friday. Liberia should reach about 32 C (90 F), and Quepos about 31 C (87 F). All of Costa Rica remains on the green alert that the National Emergency Commission (CNE) declared on Tuesday. That keeps local emergency committees active in every canton. CNE president Alejandro Picado urged people to move to safe ground if rivers start to rise and to avoid crossing channels with strong currents. If you’re on the road or the trails this weekend, plan your day around the morning. Storms this week have hit hardest in the afternoon and at night. Never drive or walk through a flooded road or a swollen river. You can’t tell how deep or fast the water is until you’re in it. Stay away from riverbanks and steep slopes during and after heavy rain, and watch for fallen trees and fog on mountain routes. At the beach, be careful of the water as well as the sky. The University of Costa Rica’s marine research center forecast waves of up to 2.7 meters (8.9 feet) in the South Pacific on Friday and Saturday, following rough surf earlier this week farther north. Small boats, fishing trips and water tours face the most risk. Forecasts for systems like this can change quickly. The hurricane center updates its outlook every six hours, and IMN has warned that its weekend forecast could shift as the low evolves. Anyone with plans outdoors should check the latest update before heading out and call 911 in an emergency.