(Releads and updates throughout, pvs MEXICO CITY)
MERIDA, Mexico May 31 Tropical storm Arthur, the first of the year in the Atlantic and the second in the Americas, whipped up strong winds and dumped heavy rains on Saturday as it churned across Mexico's Yucatan peninsula.
Packing sustained winds of near 40 mph (65 kph), Arthur drenched southern parts of Yucatan as well as neighboring Belize and Guatemala, the Miami-based National Hurricane Center said. Up to 10 inches (25 cm) of rain are expected.
"These rains could cause life-threatening flash floods and mud slides, especially in mountainous terrain," the center said.
Arthur, which formed a day before the official June 1 start of the Atlantic hurricane season, was centered 75 miles (125 km) northwest of Belize City.
It was moving westerly at 7 mph (11 kph) and was expected to weaken. It is expected to cross the Yucatan, south of the colonial city of Merida and emerge intact on Sunday in the Bay of Campeche, part of the Gulf of Mexico where there are oil platforms.
"Arthur is expected to weaken to a depression tonight, but it then could regain tropical storm strength if it emerges over the Bay of Campeche," the hurricane center said.
Arthur is seen lingering in the southern part of the Gulf of Mexico until Tuesday, according to a five-day tracking forecast map from the hurricane center.
Small boats were banned from leaving a handful of ports along the Mexican Caribbean coast, according to Nemesio Medina, head of Quintana Roo state government weather center. But conditions were not bad enough to evacuate, he told reporters.
Another tropical storm, Alma, which formed in the Pacific, broke up on Friday over Central America's mountains after slamming into Nicaragua's Pacific coast, killing three people. (Reporting by Jose Cortazar; Writing by Chris Aspin)
Tropical Storm Arthur is projected to weaken tonight, but it will likely regain strength after entering the Bay of Campeche on Sunday.

The 2008 Atlantic hurricane season got off to an early start today when a tropical storm formed off the coast of Belize, one day before the season officially begins.

Tropical Storm Arthur formed Saturday afternoon and quickly made landfall at the Yucatan Peninsula, near the border between Belize and Mexico. Both countries issued a tropical storm warning for the peninsula's eastern coastline. In the Mexican state of Quintana Roo, ports were closed to small boats, water sports were banned, and those living in coastal areas were encouraged to take precautions.

The National Hurricane Center in Miami, Florida says that Arthur had a maximum sustained wind speed of 40 miles per hour (64 km/hr). These winds extend outward up to 260 miles (415 km) east of the storm's center. As of 5:00 pm EDT, the center of the storm is located 75 miles (125 km) northwest of Belize City.

The hurricane center is also expecting up to 10 inches of rain in parts of Mexico, Belize, and Guatemala, with isolated amounts of up to 15 inches. "These rains could cause life-threatening flash floods and mud slides, especially in mountainous terrain," the National Hurricane Center said.

The storm is projected to weaken into a tropical depression Saturday night. But the National Hurricane Center says it will likely strengthen back into a tropical storm after reemerging into the Bay of Campeche on Sunday. Several Mexican oil fields are located in the Bay of Campeche, including one operated by the state-owned Petroleos Mexicanos.

The National Oceanic and Atmospheric Administration (NOAA) has predicted a more active Atlantic hurricane season than normal, with up to 16 named storms and five hurricanes of Category 3 or above, which are classified as major hurricanes.