MIAMI (AP) — Tropical Storm Humberto formed in the Atlantic Ocean on Wednesday at the same time Hurricane Gabrielle was racing across the ocean toward the Azores islands, forecasters said.

A hurricane warning was in effect for the volcanic archipelago which could experience dangerous conditions from Gabrielle as early as Thursday, the Miami-based National Hurricane Center said.

The Category 2 storm is forecast to weaken but could cause significant coastal flooding in the island chain as well as large, destructive waves, forecasters said. From Thursday into Friday, Gabrielle may bring up to 5 inches (13 centimeters) of rain across the central and western Azores.

In the Northern Atlantic, Gabrielle was centered about 1,010 miles (1,625 kilometers) west of the Azores on Wednesday afternoon. It had maximum sustained winds of 100 mph (160 kph) and was traveling to the east at 28 mph (45 kph).

Waves generated by Gabrielle will continue to affect Bermuda, the U.S. East Coast from North Carolina northward and the Atlantic coast of Canada, forecasters said. Life-threatening surf and rip currents are possible.

Tropical Storm Humberto was located 550 miles (885 kilometers) east-northeast of the northern Leeward Islands with maximum sustained winds of 40 mph (65 kph), the weather center said. Humberto is expected to affect the eastern coast of the U.S. with 39 mph winds within the next five days

In the Pacific, Hurricane Narda remained a Category 2 storm while continuing to move away from Mexico, forecasters said. On Wednesday afternoon, it had top sustained winds of about 100 mph.

Narda was centered about 560 miles (900 kilometers) south-southwest of the southern tip of Mexico’s Baja California peninsula, and was moving west at 10 mph (16 kph). No coastal watches or warnings were in effect as the hurricane was expected to continue moving further offshore.

Swells generated by Narda could bring rough surf and rip current conditions to some parts of coastal Mexico, forecasters said. The hurricane was expected to weaken over the next day or so, but restrengthen on Thursday and Friday.