Gabrielle, with maximum sustained winds of near 60 mph with higher gusts -- up from 40 mph at the start of the day -- was about 25 miles south-southwest of Bermuda, heading north at 8 mph, the National Hurricane Center in Miami said in its 11 p.m. EDT advisory. The storm was expected to pass over the island within hours, the center said.
"L.F. Wade International Airport in Bermuda recently reported a sustained wind of 32 mph," the center said. "An elevated station at Commissioners Point on Bermuda recently reported a sustained win of 47 mph and a wind gust of 59 mph."
Gabrielle was pushing tropical-storm-force winds outward up to 115 miles from its center.
Gabrielle is expected to slow down, turn to the northwest and possibly grow stronger in the next day or so, the forecasters said.
Gabrielle could create a storm surge of 2-3 feet above normal tide levels as well as rough surf conditions Tuesday afternoon.
Two to 4 inches of rain could fall across Bermuda, with isolated amounts of up to 6 inches possible, forecasters said.
Farther out in the Atlantic, meanwhile, Tropical Storm Humberto was on the verge of becoming a hurricane, with forecasters saying in their 11 p.m. EDT advisory it was producing maximum sustained winds of 70 mph with gusts up to 90 miles from its center.
Humberto was about 270 miles west of the southernmost Cape Verde Islands, traveling northwest at 7 mph. It was expected to strengthen further, becoming a hurricane Tuesday night or early Wednesday.
There were no coastal watches or warnings in effect.
Humberto was expected to shift to the northwest later Tuesday, then veer to the north and pick up speed by late Wednesday.