Meteorology
East Sussex meteorology
There are reportedly 340 wrecks of ships & boats off the coast of East Sussex in the Eastbourne area alone. It’s fair to say that they’re not all the result of enemy action. Unless you include the meteorology of our local area
as ‘the enemy’.
Between Beachy Head and Cuckmere Haven, our local weather is complicated by the presence of the cliffs. The fact that they are eroding relatively quickly by historical and geological standards makes the changing coastline challenging to get at, as members and helpers of BHASSEXPLORE will have realised by now! If you are going to trek for quite a long time trapped between sea and cliff, it’s as well to bear in mind what can happen to tide and weather locally while you are doing it. It’s not exactly like waiting for the weather to change, sitting on the South Col, so you can have a go at the summit of Everest, but neither is it like lying on the beach at Birling Gap and scurrying back to the car park if it starts raining.
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We are blessed with living on the borders of four separate climate areas where the weather can ‘come from’ in E Sussex. In summer, if we are lucky, southerly winds, associated with a high pressure area (sometimes called the Azores High) lies across Europe, and brings us air from as far south as the Sahara. These are the hot days.
High pressure weather brings gently descending air, often for days at a time.
Bad visibility usually builds up as pollution is trapped, and dust from the desert falls on our cars. Good beach weather. However, the startlingly white
cliffs can cause unforeseen problems. By the way, the movie makers have over the years used our cliffs as stand-ins for the so-called ‘white cliffs of
Dover’, which are much greyer than ours. They don’t erode as fast.
Apart from being harmful to the eyes, very white surfaces reflect and magnify the
UV from the sun’s rays causing sunburn- like being spit roasted from all sides! The sun’s ability to burn depends on how much of the absorbing atmosphere it has to travel through before getting to you. The sun is at its highest in the sky around the Summer Solstice, June 21st. It the travels through the least amount of the atmosphere. In the winter it’s low on the horizon and has a lot of atmosphere to get through. Heat and UV are less. The summer heat that we experience doesn’t come directly from the sun’s rays, it comes from the earth below us which IS heated by the sun, and this takes a couple of months to build up, so August might be the hottest month, but the sun is just as strong for burning purposes in April, two months the other side of the summer solstice, catching many fair-skinned of us out. Not strictly a meteorology problem , but in association with a particular type of weather.
The cliffs DO slowly absorb heat from the sun over the season, and act a bit like old school storage heaters we had in our house as a kid. Big block of concrete, basically, heated by cheap night time electricity which slowly gave off its stored heat through the day. The chalk in the cliffs does that. On a calm sunny day in February it can make quite a difference to the temperature, together with the whiteness reflecting what heat the sun has,
especially if you’re working up close to them.
So what else may you expect if you’re working below the cliffs? Thunderstorms around the coast in Summer drifting across the channel and picking up energy from the sea are a feature of our local weather in E Sussex,
because we are liable to be influenced by Continental weather across the channel, more so than further west in the county. Same deal in winter, except this is when Kent & E Sussex can get the worst of our snow. It’s not our climate, it’s theirs! Very cold too if there are weather lows or highs in other parts of Europe that mean we get the benefit of easterly winds associated with weather that’s mainly happening elsewhere.
Sea fog can happen very quickly and catch you out. Further down the coast at Newhaven we get sea fog caused by colder, heavier air from the Ouse valley rolling down to the sea under gravity and causing the water vapourrich sea air to cool and condense out as fog.
The Beachy Head fog is different. It usually comes when a southerly airstream blows up against the cliffs. BH is high enough for the wet Channel air thus forced upwards to cool as it rises just enough to condense out as before. At the bottom of the cliff it may be clear, but foggy above you.
BH can work the other way round too, when the wind is out of the south-west, which is by far the dominant, or ‘prevailing’ direction from which the weather comes to us. Eastbourne is, allegedly the sunniest, warmest place in England.
One reason is the SW airstream. Beachy Head is subject to the ‘Föhn wind effect. These happen locally all over the world, often to greater effect with bigger hills, but the cause is the same. A moist SW wind climbs though Orographic Uplift (same deal as the BH sea fog) being forced up by the geography. It cools as it goes up and may cool enough for the moisture to condense into rain, in this case, on the windward side of BH. Eastbourne side the air can descend again. BUT because it is now dryer after losing the rain it heats up in the descent, and at a faster rate than it cooled because it’s now dryer. The ‘dry adiabatic lapse rate’. Amaze your friends in a pub quiz with that one. Dryer, warmer air with less cloud then blows over Eastbourne and gives it the sunshine capital title.
South-westerly gales blowing down the channel are all too well known. A SW airstream is the prevailing weather in the south of the U.K. Our bit of the south coast is no different.
The Channel can act as a funnel for the winds. Anybody who doubts that should go up on the Downs and look at the way the small trees and bushes are bent SW-NE, and these winds help drive the rubbish which is BHASSEXPLORE’s business
up onto the beaches and coves under the cliffs.
It’s not the tides themselves, quite high as they are around here, that deposit the detritus. Nor is it
currents. They are very slack in the Channel Little more than 1kt and can reverse direction The warm Gulf Stream that flows across the Atlantic and keeps our climate mild for the latitude we sit at, flows up and around the top of Scotland and spends itself in the northern North Sea.
It doesn’t affect us down here as a current. Flotsam tends to just go up and down with the tide, but plastics often float high and a SW wind will dive them onshore and keep them there as the tide goes out. A full-blown SW storm will entangle stuff in the rocks at any state of the tide.
I’ve tried to keep this simple, and everything to do with meteorology and forecasting always contains caveats like ‘could’, ‘might’, and ‘sometimes’.
There are complicating factors, like the arm outside Newhaven Harbour diverting the eastwards shingle drift that blocks river estuaries, but the undoubted effect has is believed not to have much effect beyond Cuckmere.
When you’re at the bottom of the cliffs, it’s just you and the tides and the
weather. As the TV weatherman says: “Enjoy the day, but take care out there!”