Published: Sep 15, 2010 11:32 AM EDT
Updated: Sep 15, 2010 8:34 AM EDT

CANCUN, Mexico (AP) - A strengthening Tropical Storm Karl neared the Yucatan Peninsula on Wednesday, bearing down on the resort beaches of the Mayan Riviera.

Karl had maximum sustained winds of about 65 mph (100 kph) and was located about 105 miles (170 kilometers) east of Chetumal, Mexico, the U.S. National Hurricane Center in Miami said.

Mexico's government issued a tropical storm warning for the peninsula from Chetumal northward to Cabo Catoche. Parts of Belize are under a tropical storm watch.

The storm was expected to smack into land near Tulum, a beach town of eco-resorts and cliffside Mayan ruins, and then quickly weaken into a tropical depression before heading back out over the Gulf of Mexico, where it could turn into a hurricane by the end of the week.

Authorities on the Yucatan warned the population of heavy rains but said they saw no need yet for evacuations.

"The police in all communities are just monitoring. There are no instructions to evacuate or activate shelters," said Didier Vasquez, deputy state public safety secretary.

The storm threw doubt over the area's celebration of Mexico's bicentennial anniversary of independence from Spain, although there was no immediate decision to cancel festivities.

Felipe Reyes, a receptionist at Las Ranitas hotel in Tulum, said guests were warned to prepare for heavy rains and winds overnight, but none had chosen to leave.

"For now everything is calm. The weather is pretty nice," Reyes said.

Meanwhile, Hurricane Julia rapidly intensified in the open Atlantic and became a powerful Category 4 storm early Wednesday. It had maximum winds near 135 mph (215 kph). Also far from land over the Atlantic, Hurricane Igor's top winds weakened slightly to 145 mph (230 kph).

None of the three storms is any threat to Southwest Florida.