Caribbean Sea: Tropical Storm Grace tracking westward in the Caribbean Sea, after landfall in Jamaica Aug. 17 /update 8

Event

Tropical Storm Grace is tracking westward in the Caribbean Sea, away from Jamaica Aug. 17. As of 23:00 EDT, the storm's center of circulation was approximately 235 km (145 miles) east-southeast of Grand Cayman, Cayman Islands. Forecast models indicate the system will continue to strengthen and make a close approach to Grand Cayman, Cayman Islands early Aug. 18. Grace is likely to strengthen further into a category one hurricane and make landfall over Quintana Roo State, Yucatan Peninsula, Mexico, early Aug. 19. After landfall, the storm is forecast to weaken rapidly into a tropical storm as it tracks west-northwest over the Yucatan Peninsula and exits into the Gulf of Mexico late Aug. 19. Grace is likely to strengthen into a category one hurricane as it tracks westwards in the Gulf of Mexico towards central Mexico through late Aug. 20 and make another landfall as a category one hurricane over Veracruz State early Aug. 21. After landfall, the system will weaken rapidly as it tracks westwards across Mexico through Aug. 22 and transitions into an extra-tropical cyclone over western Jalisco State late Aug. 22. Some uncertainty remains in the track and intensity forecast, and significant changes could occur in the coming days.

Government Advisories
As of 23:00 EDT Aug. 17, the following warnings and watches are in effect:

• Hurricane Warning: Yucatan Peninsula, Mexico, from Cancun to Punta Herrero, including Cozumel

• Hurricane Watch: Cayman Islands

• Tropical Storm Warning: Jamaica; the Cayman Islands; the southern coast of the Cuban provinces of Granma, Las Tunas, and Camaguey; Yucatan Peninsula, Mexico, from north of Cancun to Dzilam as well as from south of Punta Herrero to Puerto Costa Maya

• Tropical Storm Watch: The southern coast of the Cuban provinces of Ciego de Avila, Sancti Spiritus, Cienfuegos, Matanzas, and Pinar del Rio, and Isla de la Juventud; the north and west coasts of the Yucatan Peninsula, Mexico from west of Dzilam to Campeche

Officials could issue new warnings and/or watches in response to the developing system in the coming days.

The Jamaica Public Service Company (JPS) has reported that some customers are without electricity. The worst affected include Kingston, St. Andrew, St. Catherine, St. Thomas, Portland, St. Mary, and St. Ann parishes.

Hazardous Conditions
The storm will likely bring further heavy rainfall, strong winds, and rough seas to coastal areas of the western Caribbean and Yucatan Peninsula, Mexico, through at least Aug. 19. Sustained heavy rainfall could trigger flooding in low-lying communities near streams, creeks, rivers, and urban areas with easily overwhelmed stormwater drainage systems. Sites located downstream of large reservoirs could experience flash flooding after relatively short periods of intense rainfall. Forecast models indicate the system will likely bring 7.5-15 cm (3-6 inches) of rainfall to Jamaica, the Cayman Islands, and portions of the Yucatan Peninsula, Mexico through Aug. 19. Torrential precipitation could trigger flash floods and mudslides.

Prolonged sea swells and storm surge generated by the system may result in coastal flooding. Persistent onshore flow could make it difficult for the surge to recede and for water levels to decrease in coastal river catchments. Storm surge is forecast to raise water levels 0.3-0.9 m (1-3 feet) above the normal tides for the Cayman Islands and 0.9-1.5 m (3-5 feet) for portions of the northeastern Yucatan Peninsula through at least Aug.19. In addition to the heavy rain, flooding, and storm surge, the storm could produce damaging wind gusts, resulting in power outages due to fallen trees and toppled utility lines.

Transport
Inclement weather associated with the storm could trigger further localized business, transport, and utility disruptions. Floodwaters and debris flows could render some bridges or roadways impassable, impacting overland travel in and around affected areas. Areal flooding in urban locations could also result in severe traffic congestion. Heavy rain and low visibility may trigger flight disruptions at regional airports.

Disruptions triggered by inclement weather and resultant hazards, such as flooding could persist well after weather conditions have improved. If there is severe damage to infrastructure, repair or reconstruction efforts may exacerbate residual disruptions.

Advice

Activate contingency plans in areas where officials forecast adverse weather conditions. Heed any evacuation orders that may be issued. Use extreme caution in low-lying coastal areas and near streams, creeks, and other waterways due to the high potential for severe flooding and storm surge. Stockpile water, batteries, and other essentials in advance. Charge battery-powered devices when electricity is available; restrict the use of cellular phones to emergencies only. Power down mobile devices when not in use. Keep important documents and necessary medications in waterproof containers. Observe strict food and water precautions, as municipalities could issue boil-water advisories following flooding events. Take precautions against insect- and waterborne diseases in the coming weeks.

Plan accordingly for protracted commercial, transport, and logistics disruptions in areas in the path of the storm, especially if vital infrastructure is damaged. Seek updated information on road conditions before driving or routing shipments through areas where flooding has occurred. Confirm flights before checking out of hotels or driving to the airport; clearing passenger backlogs may take several days in some locations.

Resources

US National Hurricane Center
National Weather Service
Cuba Instituto de Meteorologia (Spanish)
Dominican Republic Oficina Nacional de Meteorologia (Spanish)
Haiti Centre National de Meteorologie (French)
Meterological Service of Jamaica