Tropical Storm Otto has formed in the southwest Caribbean with 50 mph winds.
The system, which is the 15th named storm of the year, is expected to become a hurricane by Wednesday morning. Otto will not affect the U.S.
Forecasters announced Otto in a special 1 p.m. advisory after noting the depression had strengthened on satellite imagery.
“Additional intensification is expected and Otto could become a hurricane in 48 hours, or sooner,” forecasters wrote.
Hurricane season runs through the end of November, but it’s unusual for tropical cyclones to form this late in the year.
A tropical storm watch could be issued later today or tonight for areas including Costa Rica and Nicaragua. As of 1 p.m., Otto was about 305 miles east of Bluefields, Nicaragua.
The biggest concerns with Otto are outer rain bands that could drop 3 to 6 inches of rain across parts of Panama and Costa Rica through Wednesday.
“These rains could result in life-threatening flash floods and mud slides,” NHC forecasters said. “Additional heavy rainfall may move into portions of Costa Rica Wednesday night into Thursday as the system approaches the coast.”