Hurricane Gonzalo remains a Category 3 storm and is now 506 miles south-southwest of the Island, according to The Bermuda Weather Service’s midnight update.

The closest point of approach is forecast to be 40 miles to the west-northwest at 4pm on Friday.

The National Hurricane Centre’s 11pm update said Gonzalo was moving north at nine miles per hour and maximum sustained winds have decreased to 120mph, with higher gusts.

A turn north-northeast is expected by late Thursday, with an increase in forward speed.

Hurricane-force winds are now extending outwards up to 40 miles, with tropical storm winds reaching out by 140 miles, the Centre said.

They warned a dangerous storm surge was expected to produce “significant coastal flooding” in Bermuda with large and destructive waves.

Gonzalo is expected to produce between three and six inches of rain over Bermuda.

Fluctuations in intensity are common with major hurricanes and likely to continue with Gonzalo over the next day or so.

The Bermuda Weather Service’s 9pm forecast put Hurricane Gonzalo 517 nautical miles south-southwest of Bermuda.

A Hurricane Warning was issued at 4.30pm.

The storm was upgraded to a Category 4 hurricane at midday today as it continued gaining strength over the open Atlantic Ocean.

But by the time Gonzalo arrives in Bermuda it is expected to be a Category 3 hurricane on the Saffir-Simpson scale, which ranks hurricanes from one to five. This means Bermuda could encounter winds of 111-129mph.

Hurricane Fabian in 2003 was also a Category 3 storm when it struck the Island — although the behaviour and damage inflicted by different storms will vary considerably based on local conditions and the storm’s position at the time of impact, as well as the tides.

Hurricanes are also notoriously difficult to predict and Gonzalo’s anticipated arrival is still more than 36 hours away.

At 3pm the National Hurricane Centre said Gonzalo had winds of 130mph.

A trough off the US East Coast should cause the system to angle towards Bermuda.

Forecasts also show Gonzalo degrading to a Category 2 hurricane as it continues into the Atlantic to Bermuda’s northwest on Friday afternoon.

This is the first Category 4 hurricane in the Atlantic basin since Ophelia in 2011.

We will continue to update this article throughout the day.