Hurricane Irene bore down on the Turks and Caicos Islands Tuesday as the category two storm steamrolled on a track that could whip the Bahamas and slam the US mainland later in the week. Forecasters said Irene, now packing winds of 100 miles (160 kilometers) per hour, could become a major hurricane by Wednesday as it swirls past a series of islands toward the US east coast. Airports closed on the island of Providenciales, banks and supermarkets shut their doors, and long lines formed at gas stations in anticipation of the stormy weather set to hit the British overseas territory of Turks and Caicos. "The anticipation of the unknown is almost always the worst part of this waiting game," said Tim Ainley, 60, a long-term resident, after moving his handcrafted catamaran to the shelter of a canal. "I am now preparing my house and getting everything off the floor in case of flooding," he told AFP. Turks and Caicos spokeswoman Andrea Been said storm surges and battering waves would strike the islands later Tuesday and into nighttime. Heavy downpours are expected to result in widespread flooding, with residents urged to remain on high alert. In the Dominican Republic, authorities said they managed to move some 7,000 people to shelter before the storm winds brushed the island's north coast Monday night. "It's still raining a lot," said Jose Luis German, deputy director of the Dominican Republic's Emergency Operations Center. "We've evacuated more than 7,000 people and placed them in shelters or private homes." Quake-ravaged Haiti, which shares the island of Hispaniola with the Dominican Republic, was largely spared the storm, although some mudslides were reported near the northern coast. In Cuba, authorities began making preparations in its eastern provinces for Irene, which is projected to skirt past the island. Irene is forecast to approach the US mid-Atlantic coast likely to be packed with tourists for one of the final weekends of summer. The storm is expected to strengthen, reaching category three strength by Wednesday, the US National Hurricane Center said. And forecasters said that by the time Irene reaches US shores, it is likely to be an even more potent storm -- perhaps as high as a category four on the five-level Saffir-Simpson scale. "The stakes are high because it would take just a slight shift in the track to the left to make a dramatic change in the impact of the storm in a hugely populated area," said Dennis Feltgen, a spokesman for the NHC. US forecasters said Irene could travel clear up the US Atlantic coast as far north as Delaware by early Sunday. At 1500 GMT, Irene was centered 70 miles (110 kilometers) south-southeast of Grand Turk Island, the Miami-based US National Hurricane Center said. Tropical storm-force winds extended outward as far as 205 miles (335 kilometers) from the eye of the storm, which was expected to pass over the Turks and Caicos and then the Bahamas. Fed by warm Atlantic waters, the intensifying storm is expected to whip up ocean storm surges of as high as 13 feet (nearly four meters) by the time it reaches the central Bahamas. Up to 10 inches (25 centimeters) of rainfall, meanwhile, were expected in the southeastern Bahamas and the Turks and Caicos Islands. The Bahamas National Emergency Management Agency (NEMA) issued an advisory urging necessary precautions to secure property as well as persons. Earlier, Irene ravaged the US territory of Puerto Rico on Monday, leaving nearly a million people in the dark. Clean-up was underway after Irene downed trees and caused flooding in residential areas. After the storm hit, US President Barack Obama issued an emergency declaration for Puerto Rico.