Sun, sea and…haar. That’s pretty much been the keynote of summer in parts of Courier country this summer.
The word haar comes from the Old Norse word meaning hoary, and interestingly the modern Dutch word for bitter cold is hare.
Certainly, there’s nothing more disappointing than getting ready for a day at the beach or in the garden and then having to scupper your plans as a cold mist rolls stealthily inland a literal wet blanket.
There are even reports of locals moving house to get away from the coast to try to ensure a few more sunny summer days.
Cult weather guru Windy Wilson, famous for his colourful weather forecasts for Perthshire and the rest of the UK on Facebook, explains: “A haar is simply a coastal fog. There’s no difference between mist, fog or haar, except in terms of density and visibility fog tends to be thicker so visibility is poorer.
“In the eastern parts of Scotland and north east England as far as Newcastle, it’s referred to as a haar, but further south people call it a sea fret.”
So where does it come from and how does it form?
“Relatively warm air from Europe and the Mediterranean gets blown in over a cooler surface, usually the sea or a wide river,” says Windy. “When it creeps up the Tay it’s quite spectacular but eerie.
“There are some fabulous pictures of a train coming out of the haar on the Forth Rail Bridge.
“A haar can be pretty fast-moving so it can be quite dangerous for train drivers in these conditions. Also, for anyone walking on coastal paths it’s best to be prepared with a compass and warm clothing,” he advises.
“If you imagine a warm fluffy ball of cloud wafting over the sea, the sea cools down the warm air and condenses it to form water particles.
“The clouds can’t hold the moisture any more so they drop and creep inland. It’s impossible to tell how far in it will go because it depends on the temperature of the land.
“On Wednesday this week it went in as far as Inverbervie, between Dundee and Stonehaven and the temperature only made it to about 13 degrees C. Compare that to the west coast which hit almost 30 degrees C in places.”
It’s difficult to predict how long a haar will last if the land is warm when the fog rolls in from the sea, it will disperse more quickly, because of a smaller temperature difference between the surface of the earth and the air. Other factors include wind speed and direction, the temperature of the sea and air humidity levels.
“I actually thought the haar would last longer yesterday,” admits Windy. “Because of Wednesday’s haar, the land temperature would have been cooler, meaning it takes longer to burn it off and evaporate the following day but I was pleasantly surprised to find that it was a scorcher from about 10am.”
Haars can often come in at night, as Windy explains: “The last few nights have been warm and muggy but if warm air comes in over cooler land then the mist will form.
“You’ll often see it sitting on the top of rivers and lochs in the winter. It’s all about relative temperatures even though the ‘warm’ air could be freezing it’s still warmer than the surface it’s going over.
“Haars are most common from spring to mid-summer though,” he continues. “In the spring the land is still cold from the winter but by the end of August, start of September, the land has really warmed up so, because everything’s more or less at the same temperature, we hardly get haars then.”
And it’s not just the UK that’s affected by this weather phenomenon. Windy adds: “I once saw the Golden Gate Bridge in San Francisco after the mist had rolled in it looked as if the bridge was coming out of the clouds. Spectacular!”
Photo courtesy of the Dundee Satellite Receiving Station.