Humberto was predicted to pass just to the north of Bermuda, but a small shift in track could bring the storm over the island itself.
Humberto was still more than 500 miles from the island on Tuesday, with top sustained winds of 100 mph.
A hurricane warning is in effect for the Bermuda, meaning hurricane conditions are expected within 36 hours.
The center says Humberto is a large storm with hurricane-force winds extending 60 miles (95 kilometers) from the center.
Caines said Thursday that, "The worst of it is behind us".
NASA's Terra Satellite provided a visible image of Hurricane Humberto when it was off the coast of the Carolinas and slowly moving north.
"While Humberto and Kiko were spinning in the Atlantic and Eastern Pacific, 4 new tropical cyclones formed Tuesday: Imelda and Jerry in the Atlantic Basin and Mario and Lorena in the Eastern Pacific Basin", The Weather Channel reported.
According to the National Hurricane Center, some development of this system is possible over the weekend while the system approaches the Windward Islands or across the southeastern Caribbean Sea early next week. Unsafe storm surges could cause flooding on the south coast of the main island.
Farther off Mexico's Pacific Coast, tropical storm Mario also was expected to be a hurricane by Friday as it approaches the southern tip of Baja California and becomes almost stationary through Friday night. The risky weather system is expected to wreak havoc along the southwestern coast on Thursday as strong winds and heavy rains spread northward. The National Hurricane Center says the system is expected to drop significant amounts of rain over Texas - 5 to 10 inches or even more in isolated areas.
Tropical Storm Jerry is now a hurricane, closing in on the outermost Caribbean islands with top sustained winds of 75 miles per hour (120 kph).
As Imelda moves closer to Houston it will weaken back down to a tropical depression on Wednesday but this system still looks to bring a lot of rain to the region.
Humberto was centered about 490 miles (785 kilometres) west-southwest of Bermuda, moving to the east-northeast at 9 mph (15 kph).
During a Category 1 hurricane, impacted areas should expect damage to the roofs of well-constructed homes, power outages and snapped tree limbs.