Tropical Storm Barbara may strengthen over the next two days to become the first hurricane of the eastern Pacific season as it moves toward southeastern Mexico, U.S. and Mexican forecasters said.

Barbara had tropical storm-force winds of 47 miles per hour (75 kilometers per hour) as of 9 a.m. Mexico City time, Mexico's National Meteorological Service said. It was 155 miles (250 km) south of Oaxaca's Puerto Angel, and heading southeast at 2 mph.

''Interests along the Pacific coast of southeastern Mexico and Guatemala should closely monitor the progress of Barbara,'' the U.S. National Hurricane Center said in an advisory on its Web site. The center's five-day forecast shows Barbara becoming a hurricane by June 2, reaching the Mexican coast a day later.

Barbara may bring ''intense rain that may generate landslides in mountainous areas and floods in low-lying and coastal areas.'' the Mexican agency said. Oaxaca, Guerrero and Chiapas states may be affected, it said.

Barbara is the second named system of the eastern Pacific hurricane season, which began May 15. Tropical Storm Alvin formed earlier this week and was heading west, away from land, after weakening to a depression. It was forecast to dissipate by late today, the U.S. center said.

The Atlantic season officially begins tomorrow and ends Nov. 30, although the first named storm, Andrea, formed three weeks ago off the southeastern U.S. coast. As many as five major hurricanes may form in the Atlantic Ocean this year, fueled by above-normal sea temperatures, according to U.S. forecasters.

The systems are named when sustained winds reach 39 mph, and become hurricanes when winds reach 74 mph.