Hurricane Gabrielle has developed in the open Atlantic, southeast of Bermuda, strengthening into a Category 1 storm on Sunday, while Tropical Storm Narda emerged off southern Mexico's Pacific coast.
According to the Miami-based National Hurricane Center, Gabrielle's sustained winds reached 75mph (120kph).
The hurricane was located approximately 320 miles (515 kilometres) southeast of Bermuda, tracking north-northwest at 10mph (17kph).
Forecasters anticipate Gabrielle could undergo rapid intensification over the coming day or so, potentially becoming a major hurricane early this week.
Its current trajectory suggests it will pass to the east of Bermuda on Monday. A hurricane hunter aircraft confirmed the storm's hurricane strength and its north-northwestward movement.
But the center said a more northerly course was expected Monday. No coastal watches or warnings are in effect, but meteorologists urged experts in Bermuda to keep a close watch.
Large ocean swells kicked up by Gabrielle are impacting Bermuda and are expected to reach the Eastern Seaboard from North Carolina northward into Atlantic Canada over the coming days.
In the Pacific, Narda emerged well offshore of Mexico on Sunday afternoon and posed no threat to land.
The hurricane center said Narda had top sustained winds of about 40 mph (65 kph) and was positioned about 240 miles (386 kilometers) south-southeast of Zihuatanejo, Mexico, while moving to the northwest at 10 mph (17 kph).
The center says Narda could become a hurricane while heading further offshore.
During a recent period of strong weather, heavy rains forced the closure of schools, businesses, and government agencies in the US Virgin Islands on Thursday.
A widespread power outage was also reported in St. John and St. Thomas. Forecasters warned of flooding, landslides and dangerous river surges across the US Virgin Islands and in parts of neighboring Puerto Rico.
The National Weather Service said a tropical wave combined with a nearby trough, which is an area of relatively low pressure, was to blame for the heavy rains.
This year's Atlantic hurricane season has been relatively quiet, with no named storms for about three weeks and only one named hurricane. Experts say there are a few reasons for that, but it doesn't mean dangerous systems won't form later.
The Atlantic hurricane season ends on November 30.
