The storm had maximum sustained winds near 105 mph, significantly stronger from a day earlier, when winds of 80 mph were recorded. At 11 a.m. EDT, Helene was centered about 935 miles east-northeast of the northern Leeward Islands and moving northwest at 10 mph.
Helene's speed makes it a strong Category 2 storm and the National Hurricane Center said the season's fourth hurricane could strengthen further.
Still, the storm, like Hurricane Gordon, posed no immediate threat to land.
At 11 a.m. EDT, Gordon had top sustained winds near 80 mph, up slightly from earlier Sunday. Its ragged eye was centered about 1,495 miles west of the Azores and moving north near 10 mph. to a Category 1 storm Friday.
Gordon was moving significantly faster than Saturday, when forecasters said it was inching along at 3 mph. The hurricane center said it expected Gordon's speed to continue to gradually increase.
Meanwhile, Hurricane Lane after pounding the resort of Mazatlan as a Category 3 storm.
The National Hurricane Center's latest forecast for the season expects between seven and nine hurricanes, a slight reduction from earlier predictions.
Scientists said this week that weak El Nino conditions had inhibited hurricane development by bringing higher ocean temperatures that increase crosswinds over the Caribbean. The winds can rip storms apart or stop them from forming.
But National Oceanic and Atmospheric Administration scientists warned that the El Nino effect on hurricanes has been small so far. And the season, which lasts until Nov. 30, is still at its traditional peak.