MIAMI -- The U.S. National Hurricane Center posted a tropical storm warning on Monday for the Gulf of Mexico coast near the Texas-Louisiana state line. As of late Monday morning, the potential tropical cyclone was centred about 130 miles (210 kilometres) south of Morgan City, Louisiana, with maximum sustained winds of 35 mph (55 km/h). It was forecast to strengthen into a named tropical storm by Monday night. In the Pacific Ocean, Tropical Storm Lowell was about 785 miles (1,260 kilometres) southeast of Hilo, Hawaii, and moving west with maximum sustained winds of 65 mph (100 km/h). Forecasters said Lowell could rapidly intensify as a hurricane by Monday night or Tuesday and reach the vicinity of the Hawaiian Islands later this week. Elsewhere in the Pacific, Hurricane Karina strengthened Monday into a powerful Category 4 storm, but isn’t threatening land, forecasters said. Karina has intensified quickly since becoming a hurricane Sunday, fueled by warm waters far from any shore. It was centred about 1,055 miles (1,700 kilometres) west-southwest of the southern tip of the Baja California peninsula of Mexico and moving west, with maximum sustained winds of 140 mph (220 km/h), the centre said. There were no coastal watches or warnings in effect, but waves were expected to affect Mexico and likely Southern California. Additional strengthening was possible on Monday, followed by fluctuations in intensity, the Miami-based centre said.