The yellow warning is in place from 6pm on Monday until midday on Tuesday, with the impact limited to the south east of the province.
And the timing couldn't be more apt: Monday is the peak of the Atlantic hurricane season, when storm activity is historically at its highest.
Given the lack of deep convection to sustain the cyclone, continual gradual weakening is expected.
Meanwhile in the Pacific, Tropical Storm Olivia was close to Hawaii, where tropical storm warnings and watches are in effect, according to the Pacific Hurricane Center.
A Met Office spokeswoman said: "Storm Helene is expected to bring a period of very strong winds to western parts of the United Kingdom late Monday and for a time on Tuesday". Tropical storm conditions are possible within the tropical storm watch area, also beginning late this morning. Vertical shear is expected to increase and turn more northwesterly during the next 36 hours, and Isaac's structure could degrade further over the next day or two.
Florence is now 485 miles from Wilmington, North Carolina.
Forecasters said Wednesday that Florence's wind field is expanding, making it a large, stable hurricane with a clearly defined eye at its center. The storm is now moving northwest at 15 miles per hour.
Isaac was moving west Wednesday afternoon at a speed of nearly 17 miles per hour.
As indicated by the National Hurricane Center (NHC), tropical Hurricane Florence, a Category 4 storm with 140 miles per hour winds, is required to make landfall somewhere close to North Carolina, South Carolina, and the Mid-Atlantic states on Thursday night or Friday morning. Coastal areas in both Carolinas have taken steps to evacuate residents and tourists, including a mandatory evacuation in SC.
Isaac is expected to produce up to 3 inches of rain, with isolated maximum totals of up to 5 inches, across southeast Puerto Rico.