Isaac Heads for the Dominican Republic and Haiti as Joyce Forms in the Atlantic

23-Aug-12

Tropical Storm Isaac is moving west through the eastern Caribbean Sea with 40 mph sustained winds. The storm is expected to become a hurricane before reaching the big island of Hispaniola around midday Friday, August 24, and cross Haiti's Tiburon Peninsula. Pockets of regions in Haiti and the Dominican Republic could receive up to 20 inches of rainfall from this event. Given the uncertainty in the extended forecast storm intensity and track, it is too early to tell the probable impact of Isaac on the US Mainland. Isaac could become a threat to southern Florida by Monday, August 27. Meanwhile, tropical storm Joyce emerged as the 10th named storm of the 2012 Atlantic Season. Joyce is currently not expected to pose any threat to the United States.

The core of Isaac currently remains poorly defined, and at times has been found to have multiple vortices. Isaac's maximum winds have dropped slightly in the past 24 hours because of the storm center's disorganization. Isaac has had a difficult time sustaining thunderstorms around its core due to very dry air at mid-levels of the atmosphere. Within the next day or so, the unfavorable dry conditions should diminish and Isaac is expected to begin a strengthening phase, and may become a hurricane before reaching the Dominican Republic and Haiti on Friday.

A hurricane warning is in effect for Haiti and the southern coast of the Dominican Republic, and tropical storm warnings remain in effect for the British Virgin Islands and Puerto Rico as Isaac passes well to the south.

Tropical Storm Isaac Potential Storm Track - August 23, 2012

Tropical Storm Isaac Potential Storm Track - August 23, 2012
Source: National Hurricane Center (NHC)

As of 11 am EDT, Thursday, August 23, the center of Isaac was located at latitude 15.6N, longitude 65.4W, and was 200 miles south-southeast of San Juan, Puerto Rico. Maximum sustained winds are 40 mph, and some strengthening may occur over the next two days. Isaac could become a hurricane before reaching the Dominican Republic and Haiti on Friday. Isaac is moving to the west at 15 mph, and a turn to the west-northwest is expected later today. This turn should bring the center of Isaac to Haiti and the Dominican Republic by midday Friday. Heavy rainfall of between 8 and 12 inches is expected in Haiti and the Dominican Republic as Isaac passes, with isolated maximum rainfall amounts to 20 inches. These heavy rains will cause flash floods and mudslides.

Currently, there is significant uncertainty in the extended forecast storm intensity and track to generate a reliable prediction on the impact of the storm on the US mainland.

Elsewhere, Tropical Storm Joyce formed in the tropical Atlantic at 11 am EDT Thursday, August 23, 2012. Joyce was located at latitude 15.2N, longitude 42.2W, about 1305 miles east of the Lesser Antilles. Joyce has maximum winds of 40 mph and little change in strength is expected over the next several days. The storm is moving at 17 mph to the west-northwest, and this motion should continue through Saturday, August 25. The extended forecast has Joyce strengthening on Sunday and Monday and turning northward. It is possible that Joyce may affect Bermuda on Monday, August 27.

EQECAT will continue to monitor these events and provide update as more information becomes available.

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