Caribbean Sea: Hurricane Grace tracking west-northwestward in the Caribbean Sea, west of the Cayman Islands, Aug. 18 /update 9

Event

Hurricane Grace is tracking west-northwestward in the Caribbean Sea, west of the Cayman Islands, Aug. 18. As of 11:00 EDT, the storm's center of circulation was approximately 105 km (65 miles) west of Grand Cayman, Cayman Islands, and 560 km (350 miles) east of Tulum, Mexico. Forecast models indicate the system will strengthen as it continues to move west-northwestward before making landfall in 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-northwestward over the Yucatan Peninsula and exits into the Gulf of Mexico by late Aug. 19. Grace is then likely to strengthen again into a Category 1 hurricane as it tracks westward in the Gulf of Mexico toward central Mexico through late Aug. 20. The system is subsequently forecast to make another landfall as a Category 1 hurricane over Veracruz State early Aug. 21. After this landfall, the system will rapidly weaken as it tracks westward across Mexico and will likely transition into a post-tropical cyclone by the time it reaches Jalisco State early Aug. 22. Some uncertainty remains in the track and intensity forecast, and significant changes could occur in the coming days.

Government Advisories
As of 11:00 EDT Aug. 18, the following warnings and watches are in effect:

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

• Tropical Storm Warning: the Cayman Islands; Yucatan Peninsula, Mexico, from north of Cancun to Campeche, as well as from south of Punta Herrero to Puerto Costa Maya

• Tropical Storm Watch: The southern coast of Pinar del Rio Province, Cuba, and Isla de la Juventud

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

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 10-20 cm (4-8 inches) of rainfall to the Cayman Islands and portions of the Yucatan Peninsula and Veracruz State in Mexico through Aug. 20. 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 by as much as 0.9-1.5 meters (3-5 feet) above normal tide levels for coastal portions of the Yucatan Peninsula through at least early 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)
Meteorological Service of Jamaica