Sea fret - a look at the foggy phenomenon which spoils sunny days in Hartlepool
It’s a common experience in spring and summer: you can be less than a half mile from the coast enjoying clear skies and sunshine - only to be faced with a wall of thick, cooling fog when you head towards the beach.
Equally, people living right on the coast can awake to find a wall of fog and chilly weather, only to discover it is sunny and warm when they pop to the shops in their coat.
Sea fret is a peculiar phenomenon which takes the edge off our warm summer days here in the North East – and it can be so thick and dark so as to appear like smoke
Officially known as "coastal fog" by weather experts, it is more commonly known as fret or sea fret here in the North East and other parts of eastern England, and is known as “haar” in parts of Scotland.
How does sea fret form?
Coastal fog is usually what is known an "advection fog" - which means it occurs when relatively warm, moist air passes over a cool surface - such as the North Sea, which is why it affects us so much in this part of the country.
The cold air which sits just above the sea's surface cools the warm air above it until it can no longer hold its moisture. This forces it to condense into tiny particles of water which form the fog that we see.
Sea fret usually occurs in the spring and summer months when conditions begin to warm up but the sea, which warms more slowly, stays relatively cold.
What makes sea fret form such thick fog in the North East?
The extent, movement and location of sea fret - and the level at which it impacts on our lives - changes according to other weather conditions.
Wind strength, wind direction and land temperature can all change the nature of sea fret. When the wind blows from the east - which is common for us in the North East - the fog will rapidly cover the coast in a blanket of fog.
This is why we have that affect some days where the beaches suddenly disappear, but it's still blue skies and sunshine even a few minutes' walk away.
If the land temperature is warm the fog can quickly disappear as the parcel of air warms. But if the land temperature is cooler, the fog can linger for a longer time.
The impacts of sea fret
While it can put the dampeners on our trip to the beach, and mean coastal dwellers missing out on the rays their counterparts a bit further in land are enjoying, sea fret does present some more serious concerns.
The sudden onset of coastal fog can sometimes be dangerous, as it causes disorientation and dramatically reduces visibility. Police and traffic agencies often issue warnings over sea fret asking drivers to take care.
It can also affect industries such as shipping and oil platforms where it has been known for stubborn coastal fog to disrupt productivity for long periods.