A man exercises under pouring rain during Isaias storm in Santo Domingo, on July 30, 2020. (Photo by Erika SANTELICES / AFP)
A man exercises under pouring rain during Tropical Storm Isaias in Santo Domingo, Dominican Republic, July 30, 2020.

Tropical Storm Isaias could strengthen into a hurricane and threaten the East Coast after battering Puerto Rico and the Dominican Republic, according to U.S. forecasters. 

The U.S. National Hurricane Center (NHC) has issued a tropical storm watch for parts of Florida’s east coast, and the government of the Bahamas issued a similar warning for swaths of its territory.  

Other areas under a tropical storm watch or warning include parts of Haiti, the Dominican Republic, and the Turks and Caicos Islands. 

A tropical storm warning means that tropical storm conditions are expected somewhere within the warning area within 36 hours. A tropical storm watch means that tropical storm conditions are possible within the watch area, generally within 48 hours. 

Isaias was moving northwest at 32 kmh (20 mph), and its center was expected to hit the southeastern Bahamas by late Thursday night, according to the NHC.  

The latest forecast map showed Isaias striking the Florida coast as a hurricane Saturday afternoon and working its way up the Atlantic seaboard.  

A man guides a tow truck under a downed power line pole after Tropical Storm Isaias hit the area in Mayaguez, Puerto Rico, July 30, 2020.

President Donald Trump has signed an emergency declaration for Puerto Rico, which has yet to fully recover from 2017’s Hurricane Maria and a recent series of earthquakes. 

Tropical Storm Isaias knocked out power across Puerto Rico and caused widespread flooding and a number of small landslides. More than 100,000 people were in need of fresh water. 

Emergency workers had to rescue several families who were reluctant to leave their homes for public shelters because of the coronavirus.  

Isaias also blew down trees in the Dominican Republic. Police arrested surfers who refused to heed warnings to find shelter. 

Isaias is the ninth named storm of a busy Atlantic hurricane season. This is the earliest date a storm beginning with the letter “I” has formed.