According to catastrophe modeling firm AIR Worldwide, late last week, a wave off the west coast of Africa, 91L, began to slowly organize as it moved west across the Atlantic. Monday night, 91L formed a closed surface circulation and developed into the fifth named storm of the 2011 Atlantic hurricane season, Tropical Storm Emily. As of the National Hurricane Center’s (NHC) 11:00 AM EST advisory, the storm is located approximately 270 miles southeast of San Juan, Puerto Rico, and is currently near stationary in the Caribbean Sea, 160 miles west of Dominica in the Lesser Antilles. Reconnaissance flights indicate that Emily remains a poorly organized system, and maximum sustained winds are currently 40 mph. Emily is expected to resume a 12 mph west or west-northwest track later today.
“While the storm is currently in an environment of low vertical wind shear, a dry dust-laden layer of atmosphere, known as the Saharan Air Layer, is located just to the north, which is currently hindering Emily from intensifying significantly,” explained Scott Stransky, scientist at AIR Worldwide. The official NHC forecast has the system strengthening slightly, although it is not expected to become a hurricane (which requires maximum sustained wind speeds of 74 mph or greater).
“Emily is forecast to pass over Hispaniola tomorrow afternoon, where its interaction with the mountainous terrain is expected to weaken the system,” said Stransky. While the winds from the storm will not be severe, 4 to 6 inches of total rainfall accumulation (with isolated pockets of up to 10 inches in the mountains) are expected in Puerto Rico, the Dominican Republic, and Haiti, creating the potential for deadly flash flooding and landslides. A tropical storm warning is currently in effect in these three territories, and a tropical storm watch is in effect for the U.S. Virgin Islands.
According to AIR, residential structures in the Dominican Republic are typically of reinforced masonry and unreinforced masonry construction, both of which can sustain damage at high flood levels. Commercial structures are predominantly reinforced concrete and reinforced masonry, which typically withstand flood damage well. However, poorer construction types away from the cities and in the mountains may not fare as well. In 1993, a weak storm with a similar track, Tropical Storm Cindy, caused several millions of dollars of flood damage (in 1993 dollars) in the Caribbean.
“After exiting Hispaniola, Tropical Storm Emily is expected to reorganize and a deep mid-level trough over the western Atlantic is expected to steer the storm more to the northwest as it passes through the Bahamas,” added Stransky. “From there, a turn toward the north is expected by Saturday morning, which may keep Emily from making a direct landfall on the Atlantic coast of Florida and the rest of the U.S. East Coast. There is, however, considerable uncertainty in Emily’s track and intensity at this point. A few computer models have the storm dissipating after passing Hispaniola, while some others take the storm much closer to the southern tip of Florida.”
Source : AIR Worldwide