Grace approaching Dominican Republic and Haiti, heavy rainfall expected

Tropical Depression "Grace" is approaching the southern coast of the Dominican Republic and Haiti, rising the threat of flash flooding and mudslides across Hispaniola today. 

• Heavy rainfall is forecast across the Dominican Republic, Haiti, Cuba, Jamaica, and the Cayman Islands, potentially leading to flash, urban, and small stream flooding, with the potential for mudslides highest in Haiti and the Dominican Republic.
• Tropical storm conditions are possible over portions of Hispaniola today and tonight.
• There is a risk of some wind and rainfall impacts across southeastern Cuba and Jamaica beginning Tuesday morning, and the Cayman Islands by Tuesday night.

A Tropical Storm Watch is in effect for the entire coast of the Dominican Republic and Haiti.

At 09:00 UTC on Monday, August 16, 2021, the center of Tropical Depression "Grace" was located just south of Dominican Republic, about 260 km (160 miles) ESE of Port au Prince, Haiti. Its maximum sustained winds were 55 km/h (35 mph) and the system was heading W at 24 km/h (15 mph). Its minimum central pressure was 1 010 hPa.

A W to WNW motion is expected over the next several days with little change in strength during the next day or so.

Tropical Storm "Fred" (top left), Tropical Depression "Grace" and Tropical Depression 8 (top right) at 09:20 UTC on August 16, 2021. Credit: NOAA/GOES-East, RAMMB/CIRA, TW

Slow strengthening is expected to begin by Tuesday, August 17.

"The evolution of the forecast track of Grace is having major implications on the future intensity of the cyclone," NHC forecaster Latto noted early Monday morning.

"It is becoming more likely that the system will track over only the southern portion of Hispaniola, which would result in a lesser disruption of Grace's circulation.

"Furthermore, the more southern track would bring the cyclone over the warm waters of the northwestern Caribbean beginning on Tuesday."

By midweek, Grace may interact with the Yucatan Peninsula, which should limit strengthening or perhaps weaken the system depending on the track.

Once over the western Gulf of Mexico, some additional strengthening is expected, although the wind shear is forecast to increase slightly during that time frame.

According to the NHC, the system is expected to produce the following rainfall amounts:

Over Haiti and the Dominican Republic, 125 – 250 mm (5 to 10 inches) of rain with isolated maximum totals of 380 mm (15 inches) are expected across the southern terrain areas through Tuesday. This heavy rainfall may lead to flash and urban flooding, and possible mudslides.

Over Cuba, Jamaica, and the Cayman Islands, Grace is expected to produce 50 to 100 mm (2 to 4 inches) of rain, with isolated maximum totals of 150 mm (6 inches) expected through Thursday, August 19.

Swells generated by Grace will continue to affect portions of Hispaniola and Puerto Rico over the next day or so, and will spread westward to Jamaica and the southern portions of Cuba.

These swells are likely to cause life-threatening surf and rip current conditions.

Search and rescue operations are still in progress in Haiti after the violent M7.2 earthquake on August 14. 

The Haitian Civil Protection Agency (DPC) confirmed 1 297 fatalities at 22:52 UTC on August 15 – 1 054 in the South, 122 in Nippes, 119 in Grand'Anse, and 2 in the North-West.

Forecast models

Featured image: Tropical Depression "Grace" at 09:20 UTC on August 16, 2021. Credit: NOAA/GOES-East, RAMMB/CIRA, TW