Remnants of Hurricane Bertha could bring a wet and windy weekend

Following a pretty good summer so far with sunshine and warmth, we could have a rude awakening later this weekend as the remnants of a hurricane bring us wet and windy weather.

Now before you all start panicking and thinking that there’s going to be an October 1987 type storm on the way, no there isn’t. And no, I don’t plan on having my own Michael Fish moment.

Nevertheless, there does look to be the potential to see a spell of unseasonably wet and windy weather during Sunday and into Monday, possibly causing some disruption. 

The cause of this potentially disturbed spell of weather is Tropical Storm Bertha, which briefly became a category one hurricane, and is currently around 3,500 miles away off the east coast of the US.

However, during the next few days, it will weaken and lose its tropical characteristics before being caught up in the jet stream and converting to an active area of low pressure over the Atlantic.

Why Bertha can’t be a hurricane when she reaches us

Hurricanes need a number of ingredients in order to form and exist, with one of the main requirements being warm ocean waters with a temperature of 26C or above.

This provides a source of warmth and moisture that can rise up in to the atmosphere and act as fuel for the storm.

So, at the moment, Bertha is a storm that has tropical characteristics, driven by warm ocean waters with a temperature of around 26C.

However, as it drifts northwards towards the coast of Newfoundland in the coming 48 hours, it will encounter much cooler waters of around 18C and thus be starved of the energy source to remain tropical.

This stands for when it approaches us too, with sea surface temperatures around the UK ranging from 14C around Scotland, to around 18C for southern England.

Still potential for gales and heavy rain

Even though Bertha will no longer be tropical, once her remnants are caught up in the jet stream, the energy and moisture will be recycled into a traditional mid-latitude area of low pressure.

This is where the huge level of uncertainty lies. Weather computer models don’t tend to handle the remnants of former hurricanes or tropical storms very well when they arrive at our latitude.

It’s often because of the huge amount of moisture and potential energy that they contain, with the interaction with the jet stream playing a crucial role.

If engaged by the jet stream, then the hurricane remnants can spawn deep areas of low pressure bringing gales and heavy rain.

On the other hand, if the jet stream doesn’t engage with this moisture and potential energy, then low pressure is less likely to form and the end result can be very different.

What can we expect?

The range of outcomes being predicted by the different computer models is still varying greatly, although they all put the remnants of Hurricane Bertha close to or over the UK during Sunday into Monday.

Having seen this type of thing happen in previous years, I think that there will be a spell of heavy rain with possibility of gales, with gusts in the range of 40-50mph, locally a bit more – especially for coastal areas.

However, it is worth emphasising that the detail will continue to change as we get closer to the time.

As ever, you can get the latest forecast on the Channel 4 Weather website. I’ll also be posting regular updates on Twitter – @liamdutton

Graphics: NOAA