BOSTON, Aug. 25, 2011 – According to catastrophe modeling firm AIR Worldwide, Hurricane Irene is passing through the central Bahamas islands this morning after a night of battering the southern islands with heavy rains and strong winds. At the time of the National Hurricane Center’s 8:00 am EDT Advisory, Category 3 Hurricane Irene was about 65 miles east-northeast of Nassau, the capital and largest city of the Bahamas. Irene’s maximum sustained winds are 115 miles per hour with higher gusts. Hurricane-force winds extend outward up to 70 miles from the center and tropical storm-force winds extend outward up to 255 miles. The storm is moving to the northwest at about 13 mph and is expected to pass directly over Abaco Island shortly. Abaco has a population of almost 17,000 people. Nassau’s population is 250,000, about 70% of the entire Bahamas.
“Irene is only the third storm to travel straight up through the spine of the Bahamas in the last 160 years, although the most recent occurrence was Hurricane Floyd in 1999, which devastated three islands,” said Scott Stransky, scientist, AIR Worldwide. According to the National Hurricane Center, Irene is expected to turn toward the north-northwest later today, followed by a turn north by early tomorrow, Friday. On the NHC’s forecast track, Irene will continue to move over the northwestern Bahamas today and then will pass-well offshore-the east coast of central and north Florida tonight and early tomorrow.
According to AIR, most houses in the Bahamas are of concrete block or poured concrete construction, usually with asphalted wooden roof tiles, although corrugated iron and aluminum roofs and Spanish tile are not uncommon. On Abaco and Eleuthra Islands, over which Irene is expected to pass today, about 20% of residential construction is timber. Most residential dwellings are single story, while commercial buildings may rise to six stories in a few cases. The Collins Avenue area of Nassau has modern buildings up to six stories in height, and a number of hotels along Nassau’s Cable Beach approach high-rise status.
According to AIR, non-engineered structures can experience significant damage to roof and wall claddings when subjected to Category 3 wind speeds and also some structural damage as well, particularly to poor-quality homes. Timber homes that are not properly anchored can sustain significant damage. Engineered structures can sustain significant non-structural damage and damage to unprotected windows caused by flying debris. Additionally, Category 3 winds will cause widespread damage to signage, trees, and poles. Business interruption losses may also be significant due both to direct physical damage to hotels and resorts, and damage to supporting utilities.
“Nassau, which has the greatest concentration of exposures, is expected to be on the western, weaker side of Irene,” said Stransky. “New Providence Island, where Nassau is situated, has a total insured value of $19.5 billion (2009 USD)-while, by comparison, the island of Abaco has a total insured value of about $1.3 billion (2009 USD). In 1999, Hurricane Floyd passed just to the east of Abaco Island. As a result, Irene will likely cause higher losses than Floyd.”
According to AIR, the Bahamas Building Code, which was implemented in the early 1970s, closely follows that of the South Florida Code, and building code enforcement in the Bahamas is relatively high.
Stransky continued, “At present, power is out throughout the Bahamas and Irene’s overnight impact on the scattered islands is just beginning to be reported. The Bahamas are made up of about 700 islands spread, north to south, over 500 miles. On Mayaguana Island (population 270) in the south, Irene uprooted trees, blew shingles off roofs, and knocked over lampposts; the entire island is without power. On Acklins Island (population 560) to the north, about 90% of the settlement in Lovely Bay has reportedly been severely damaged, and the roofs of several homes elsewhere have been blown away.”
Continuing north to Crooked Island (population 325), similar damage has been reported: some buildings have lost their roofs or had shingles blown away, and trees have been uprooted and lampposts blown over. Nassau’s downtown often floods under more normal rainfall conditions, and the city is expecting flooding, with many roads becoming impassable, especially in the colonial downtown area.
Similar, albeit less severe, damage has been reported in the Turks and Caicos Islands, through which Irene passed late Tuesday as a Category 1 hurricane. There are reports of widespread tree damage and street flooding.
AIR will dispatch a team to survey the damage in the Bahamas next week.
Stransky commented, “At present, hurricane force winds are spreading over the northwestern Bahamas: Irene stretches roughly 500 miles across, and its central core is nearly 150 miles across. Under these conditions, an extremely dangerous storm surge is expected to raise water levels by as much as seven to eleven feet above normal tide levels. Additionally, Irene is expected to produce rainfall accumulations of six to 12 inches in the next 36 hours. Already, swells generated by Irene-which will cause life-threatening surf and rip current conditions-are affecting some parts of the coast in the southeast U.S.”
Hurricane Irene’s track after the storm leaves the Bahamas remains uncertain. At present, it is expected to curve to the north, reaching North Carolina’s Outer Banks late Saturday. A slight westward shift in the NHC track brings Irene over the Outer Banks rather than just offshore has had been forecast yesterday. Irene will then move north toward New York City, possibly arriving as a Category 1 hurricane on Sunday. Such long-range forecasts have considerable uncertainty, and a slight westward-or eastward-shift in the track today or tomorrow will change Irene’s passage and have significant implications for damage and loss.
AIR is continuing to monitor Hurricane Irene closely. Additional information about losses will be made available after the storm has finished impacting all of the Caribbean islands, which-following the NHC’s current track-will be by Friday morning
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Kevin Long/Rebekka Mark