Hurricane Humberto, which strengthened from a tropical storm to a Category 1 this morning, has been deemed a potential threat to the island.

Another storm, called potential tropical cyclone nine by the Bermuda Weather Service, is brewing in the Caribbean and projected to head northwards across the Bahamas over the weekend.

If projections hold true, and it too reaches Category 1 strength next week, it would become Hurricane Imelda.

Its predicted course could have the storm approaching the South Carolina coast by Wednesday.

The BWS said in its 6pm update that Humberto lay 800 miles southeast of Bermuda, moving west-northwest at 4.5mph.

Hurricane Humberto was expected to build to a Category 4 by Monday morning, dropping again to a Category 3 as it makes its way past the island on Tuesday into Wednesday.

The BWS said that the storm’s closest point of approach to Bermuda within the next 72 hours was forecast to be about 330 miles to our south-southwest at 6pm on Monday.

It added: “Please note this forecast is subject to change at the next update.”

A BWS forecast discussion said the companion storm to Humberto’s west added uncertainty owing to “a potential Fujiwhara effect, which could still cause some significant changes in the forecast track of Humberto”.

The US-based National Oceanic and Atmospheric Administration said that a Fujiwhara effect occurs when two hurricanes spinning in the same direction pass close enough to each other to begin “an intense dance around their common centre”.

It added: “If one hurricane is a lot stronger than the other, the smaller one will orbit it and eventually come crashing into its vortex to be absorbed.

“Two storms closer in strength can gravitate towards each other until they reach a common point and merge, or merely spin each other around for a while before shooting off on their own paths.

“In rare occasions, the effect is additive when the hurricanes come together, resulting in one larger storm instead of two smaller ones.”

The BWS said that moderate to strong east-southeasterly winds were expected to veer southerly on Tuesday, strengthening overnight “with the potential for near-tropical storm force winds and higher gusts in and around showers into Wednesday”.

It added that southeasterly swells were expected to continue building moderate to rough on Monday and could develop further from the south to become very rough with dangerous conditions along South Shore.