SAN JUAN (BNO NEWS) -- Irene strengthened into a hurricane on early Monday morning after it made landfall in the U.S. territory of Puerto Rico, forecasters said, causing widespread damage and leaving more than 800,000 homes without power.
The weather system emerged as a tropical wave over the eastern Atlantic on Wednesday before it strengthened into a tropical storm on Saturday evening. It has since continued to strengthen and become better organized.
As of 8 a.m. AST (1200 GMT), the center of Irene was located about 75 miles (120 kilometers) west-northwest of San Juan, the capital of Puerto Rico. It is moving towards the west-northwest at a speed near 14 miles (22 kilometers) per hour.
Maximum sustained winds of Irene have increased to near 75 miles (120 kilometers) per hour, with higher gusts, making it a category one hurricane on the five-step Saffir-Simpson scale of intensity. Depending on its interaction with land, Irene could strengthen further.
"Irene has become much better organized during the past six hours despite its interaction with the mountainous terrain of Puerto Rico, and a ragged eye has become apparent in imagery from the [Federal Aviation Administration (FAA)] terminal doppler weather radar," said Stacy Stewart, a senior hurricane specialist at the U.S. National Hurricane Center (NHC).
Hurricane-force winds of Irene extend outward up to 15 miles (30 kilometers) from its center, while tropical-storm-force winds extend outward up to 150 miles (240 kilometers), mainly northwest and northeast of the center.
"Preliminary reports indicate that widespread tree and powerline damage has occurred on Puerto Rico, and more than 800,000 homes are without power on the island," Stewart said. "Also, FAA doppler weather radar indicates winds to near major hurricane strength are now occurring in the higher elevations of the interior mountainous regions of Puerto Rico."
On the U.S. Virgin Islands, the Virgin Islands Territorial Emergency Management Agency (VITEMA) said roadways were being cleared of debris on early Monday morning. The agency said all government employees are asked to report to work at 10 a.m. local time, although the general public is urged to remain off the road.
Stewart said tropical storm conditions were decreasing in the U.S. and British Virgin Islands, eastern Puerto Rico, Culebra and Vieques on Monday morning. "Hurricane conditions are still possible over Puerto Rico, Vieques, and Culebra this morning, and over the northern portions of the Dominican Republic later today," he said. "The highest winds are likely to occur over areas of elevated terrain."
Tropical storm conditions are further expected to reach the southeastern Bahamas, the Turks and Caicos Islands and Haiti on Tuesday, and are possible in the central Bahamas by late Tuesday. "Hurricane conditions are possible in the central Bahamas by Tuesday night," Stewart said.
It is still unclear how much strengthening will occur in the next few days, but forecasters warn there is a chance Irene could rapidly strengthen. "It now appears that Irene will not interact with Hispaniola as much or as long as previously expected. This will also result in more strengthening than previously expected," Stewart said. "Irene is forecast by all of the models to have a very impressive outflow pattern throughout the forecast period."
Warm sea surface temperature of around 30 degrees Celsius (86 degrees Fahrenheit) are also expected to encourage Irene to further strengthen. "Significant strengthening could occur. However, the official intensity will remain on the conservative side due to the uncertainty in how much Irene will interact with the mountainous terrain of Hispaniola for the next 24 to 36 hours," Stewart said.
"The official intensity forecast is a blend of the [ships and Logistic Growth Equation Model (LGEM)] models and the [Hurricane Weather Research and Forecasting (HWRF) and Geophysical Fluid Dynamic Laboratory (GFDL)] models," Stewart added. "However, given the impressive upper-level flow pattern expected across Irene, it would not surprise me if this cyclone became a major hurricane at some time during its lifetime like the GFDL and HWRF models are forecasting."
Current forecast tracks show Irene moving just along the coast of Florida by early Friday morning and making landfall in Georgia on Saturday, but Stewart said this could change. "It is important not to focus on the exact forecast track, especially at days 4 to 5 (Friday and Saturday), since the most recent 5-year average errors at those forecast times are 200 and 250 miles (321 and 402 kilometers) respectively."
Meanwhile, a hurricane warning remains in effect for Puerto Rico, Vieques, Culebra, and the north coast of the Dominican Republic from the Haiti border eastward to Cabo Engano. A hurricane watch is in effect for the central Bahamas and the north coast of Haiti from Le Mole-St. Nicholas eastward to the Dominican Republic border.
In addition, tropical storm warnings remain in effect for the U.S. and British Virgin Islands, all of Haiti, the southeastern Bahamas, the Turks and Caicos Islands, and the south coast of the Dominican Republic from south of Cabo Engano westward to the Haiti border.
Irene is the ninth named storm and the first hurricane of the 2011 Atlantic hurricane season, following Tropical Storm Harvey which remains active as a tropical depression over southern parts of Mexico.
According to figures released earlier this month, NOAA's Climate Prediction Center is expecting an above-normal hurricane season in the Atlantic this year. The outlook calls for 14 to 19 named storms, with seven to ten becoming hurricanes and three to five expected to become a major hurricane (category 3 or higher).
An average Atlantic hurricane season produces 11 named storms, with six becoming hurricanes and two becoming major hurricanes. The Atlantic hurricane season runs from June 1 through November 30, with peak activity in September.