June 1 (Bloomberg) -- Arthur, the first tropical storm of the Atlantic hurricane season, is expected to dump as much as 10 inches (25 centimeters) of rain on Mexico, Belize and Guatemala as it spins slowly west across Mexico's Yucatan Peninsula.

The rain could cause flash floods and mudslides, especially in mountainous terrain, said the Miami-based National Hurricane Center.

The storm was over land, centered 115 miles (185 kilometers) south of Campeche, Mexico, at 8 a.m. New York time, according to the center's latest bulletin. Arthur is expected to move west across the coastline of the Bay of Campeche over the next two days with maximum sustained rotational winds gradually weakening from about 40 miles per hour, forecasts showed. Storms typically lose strength when moving over land.

``Arthur is expected to weaken to a depression later today, but it could regain tropical-storm strength if it emerges over the Bay of Campeche,'' the center said.

Mexico closed ports in Quintana Roo to smaller vessels and issued storm warnings in the states of Campeche, Quintana Roo, Yucatan, Veracruz, Tabasco, Oaxaca and Chiapas, according to the Mexican Merchant Marine's weather bulletin yesterday.

State-owned Petroleos Mexicanos pumps 1.07 million barrels a day from the Cantarell field in the Bay of Campeche. The company had no immediate comment yesterday on whether operations would be affected, spokesman Carlos Ramirez said in a telephone interview.

Mexico's four major oil exporting terminals were open as of 3 p.m. local time yesterday, according to port officials.

Tropical-storm warnings, indicating the likelihood of storm strength winds within 24 hours, remain in place for the coast of Belize and the eastern side of the Yucatan peninsula.

To contact the reporter on this story: Stephen Voss in London at sev@bloomberg.net

Last Updated: June 1, 2008 09:40 EDT