At 11 p.m. EDT Monday, Ernesto was about 265 miles east of Isla Roatan, Honduras, and about 365 miles east of Belize City. The storm, with sustained winds of 65 miles per hour and higher gusts, was moving to the west-northwest at 13 miles per hour.
The hurricane center said reconnaissance aircraft found Ernesto had not strengthened in the previous several hours, though forecasters still expected the storm to become a hurricane by Tuesday evening.
Ernesto was forecast to stay on the same general track for the next two days, passing north of the coast of Honduras Monday night and Tuesday, and nearing the east coast of the Yucatan Peninsula early Wednesday.
A hurricane warning was in effect from Chetumal to Punta Allen on the Yucatan Peninsula's east coast and the entire coast of Belize.
A tropical storm warning was in effect for the coast of Honduras from west of Punta Sal to the Guatemalan border; north of Tulum to Cancun on the east coast of the Yucatan.
The center said Ernesto was expected to produce 3 to 5 inches of rain along the north coast of Honduras and the northeast coast of Nicaragua, with isolated amounts of 8 inches in the mountains. Four to 8 inches of rain were expected over the southern part of the Yucatan and Belize.
The storm is likely to cause dangerous flash floods and mudslides for higher terrain, the center said.
Forecasters said a dangerous storm surge will raise water levels by as much as 2 to 4 feet above high tide where the storm center makes landfall.
Further to the east over the Atlantic Ocean, Tropical Storm Florence earlier was losing strength and was downgraded to post-tropical status and was expected to weaken and dissipate in the next two days.