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Tropical Depression Gabrielle Lashes Puerto Rico

According to catastrophe modeling firm AIR Worldwide, in the Caribbean Sea, Tropical Storm Gabrielle formed on Wednesday night, south of Puerto Rico and the Dominican Republic.

The wave that became Gabrielle was first tracked by the U.S. National Hurricane Center off the coast of Africa back on August 25. It made its way across the Atlantic and remained disorganized until yesterday, when it was declared a tropical depression, then a tropical storm, and then back to a tropical depression. As of 11 a.m. on Thursday, September 5, Tropical Depression Gabrielle is located about 105 miles west-southwest of Puerto Rico. A tropical storm warning was issued for all of Puerto Rico and for much of the eastern portion of the Dominican Republic, but that warning has since been discontinued for Puerto Rico.

“With maximum sustained winds of nearly 35 mph (55 km/h) and a central pressure of 1011 millibars, Gabrielle is currently a relatively weak storm; it is not expected to achieve hurricane status,” said Scott Stransky, senior scientist at AIR Worldwide. “However, Gabrielle is anticipated to bring heavy rains of 2 to 4 inches – and in some isolated regions, rainfall of up to 8 inches – to Puerto Rico and the Dominican Republic, which are vulnerable to flash flooding and mudslides.”

Gabrielle is forecast to continue moving northwest at about 8 mph (13 km/h) today, causing the center of the storm to pass near or over southwestern Puerto Rico and the Mona Passage. By late Thursday or early Friday, Gabrielle is expected to degenerate to a remnant low pressure area.

Stransky noted, “Tropical Depression Gabrielle is not anticipated to cause wind damage, but may cause minimal damage due to heavy rains. Poorly constructed structures (unlikely to be insured) are susceptible to flood damage from Gabrielle’s heavy rains. Insured damage from both wind and flooding is likely to be minimal.”

According to AIR, Puerto Rico’s building stock stands out in the Caribbean, in as much as a large percentage of residential homes are made of reinforced concrete. These buildings typically have flat reinforced-concrete roof slabs, which produce a structure that is very resistant to wind damage compared to other residential construction in the region. In older urban buildings in Puerto Rico there is a greater variety of construction material used. A majority of commercial structures are low to mid-rise buildings, usually of one to six stories. Small apartments, hotels, offices, and other low-rise commercial properties are usually masonry or reinforced or block concrete. A concrete building type unique to Puerto Rico, the “bunker” style, is used for both residential and non-residential structures across the island. Bunker buildings have walls made of reinforced concrete, often reinforced with steel, combined with reinforced masonry.

Heavy rainfall of 2 to 4 inches, with isolated totals of up to 8 inches in mountainous regions, is expected in Puerto Rico, the U.S. Virgin Islands, and eastern parts of the Dominican Republic on Thursday. The National Oceanographic and Atmospheric Administration (NOAA) cautions that this large amount of rain may cause serious mudslides and flash flooding, most notably in regions with mountainous terrain. Gabrielle’s heavy rains are particularly worrisome given that the region’s year-to-date rainfall total is already 24 inches above average.

Stransky concluded, “Gabrielle is expected to degenerate to a remnant low pressure area tonight or Friday, as it moves over the Dominican Republic.”