June 21st

summer solsticemaximum insolationat the Tropic of Cancer

September 23rd

equinoxmaximum insolation at the equator

December 21st

winter solsticemaximum insolation at the Tropic of Capricorn

March 21st

equinoxmaximum insolation at the equator

Sun

Mediterranean wind systems

Change of Seasons

Tramontana

Khamsin

PonienteScirocco

Leve

che

Vendeval

Bora

GregaleVardarac

Levante Libeccio

Scirocco

Marin

Mistral

Ghibli

Scirocco

Gregale

Tramontana

Scirocco

MeltemiLevante

Scirocco

III #4 - Die wichtigsten Windsysteme im Mittelmeer

Framed by high mountains and hot landmasses, every region in the Mediterranean boasts its own wind system. Of all Mediterranean winds, the ‘Scirocco’ is particularly unusual: This dusty Northern African desert wind blows only 1-5 days a month towards the coasts of Southern Europe along a northbound ‘Saharan Low’. The hot Scirocco picks up increasing moisture the further it travels across the sea. Coming from the south-west to south-east, its

sandy load suddenly darkens the sky. This wind has many names; insouth-east Spain it’s called “Leveche”, in Morocco, Algeria, and Tunis “Chili”, in Libya “Ghibly”, and in Egypt it’s known as the “Khamsin”. A similar phenomenon is witnessed on the Canary Islands. Even though driven by entirely different weather conditions, the name and effect are the same; a Scirocco laden with Saharan dust.

The intensity of sunshine differs in the Northern and Southern Hemispheres. That’s because the Earth’s axis is tilted, and thus the angle between the plane of the Earth’s orbit around the sun and the plane of the equator varies by 23.5° through the year. This tilt and the Earth’s annual rotation around the sun create the seasonal change between summer and winter. Over the course of a year, the point of maximum solar irradiation crosses the equator twice on its travels between the Tropics of Cancer and

Capricorn. Therefore the angle of incoming solar radiation differs at any given point across the Earth’s surface. This results in the seasonal temperature contrast and also affects atmospheric circulation. After Summer Solstice – 21st June in the Northern Hemisphere – the point of maximum insolation gradually creeps southwards until Winter Solstice on 21st December. This essentially drives the migration of the global climate machinery complete with it‘s wind and weather phenomena.

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General winter weather situation

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max.

January April June October

European windspeeds < 10 - 15 - 20 - 25 - 30 - 35 - 40 - 45 - 50 - 55 - 60 - 65 > knots

THE KITE AND WINDSURFING GUIDE EUROPE THE KITE AND WINDSURFING GUIDE EUROPE 16 17

III. WIND & WEATHER IN EUROPEMeteorology & oceanography

III. Wind & Weather in Europe

While Northern Europe is indulged with consistent westerlies between 40 and 60°N (the Westerly Wind Zone), Southern Europe is broadly effected by the Subtropical Highs. With

the changing season, the summer sun slowly migrates from the Tropic of Cancer in the Northern Hemisphere towards its southern winter retreat at the Tropic of Capricorn. This shift of the global weather machinery changes the general situation in Europe too, meaning weather scenarios tangibly differ north and south of the Alps and Pyrenees.

Northern Europe

The prevailing westerlies aerate the northern coasts of Europe

– from Brittany via the British Isles up to Scandinavia – the whole year around. They’re created by a pressure difference between a pretty-much permanent low ranging from Southern Greenland via Ireland up to Norway and the subtropical high-pressure system in the region between the Azores and South-West Europe. These pressure zones predominantly concentrate around Iceland (Icelandic Low) and the Azores (Azores High). Locally, low-pressure troughs and high-pressure ridges interrupt this general flow of south-west to north-westerly winds with their subtropical or Polar air-masses. Where the cold and warm fronts border, their air-masses meet to produce precipitation at any time of year. Thus Northern Europe experiences very fluid weather conditions.

During summertime, the lows track way up north. Therefore Denmark and Western Scandinavia in particular, alongside Ireland and Scotland,

benefit from good wind conditions. Summer conditions are a bit calmer along the Southern British and other North Sea and Baltic coastlines. The lion’s share probably hits the Dutch and German Frisian Islands, which just brush the southern margins of these northern highs. Northern France and Southern England are also pretty well off due to the English Channel’s ‘Venturi’ jet-effect. Quite frequently though, low-pressure systems also take

a southern route during summertime, bringing strong winds to Northern France and North & Baltic Sea coasts. Winds might be easterly if you’re north of a low-pressure core, but persistent easterlies are rare. That said, a high over Scandinavia brings reliable easterlies to the Baltic Sea.

The low-pressure racetrack slips south in wintertime, bending Christmas trees from the North Sea to the Spanish coast. Winter storms also bring a nice Atlantic Ocean swell, although the legendary big-wave spots are only rideable between Galicia and Brittany or on the British and Irish Atlantic facing coast where the North Atlantic Drift warms the water to tolerable temperatures.

Spring and autumn provide the best mix of conditions. Powerful

lows line-up like a string of pearls over the North Atlantic, and frequently supply most coasts from Northern Spain to Scandinavia with great winds. Spring and autumn also bring plenty of waves as the storms build up a persistent Atlantic swell to pound the European coastlines. Strong winds also whip-up North Sea and Baltic waters to maximum wave heights. Conveniently, the

thermometer reads ‘good to go’ too! While spring may promise warming sunshine, water temperatures are definitely higher during autumn.

Southern Europe

The Azores High extends into the Western Mediterranean during the warm season, and at higher altitude it is even effective above the

Eastern Mediterranean. Throughout this region, nice dry weather therefore dominates the summer months. Cold fronts will occasionally disturb the Mediterranean, bringing rain and lightning.

Ambient summer winds are relatively weak in the Western Mediterranean, but its topography provides a few pleasant surprises: Framed by mountains on nearly all sides, there are precious few narrow gaps between the massifs through which the wind must make its passage. Each of those funnels acts as a jet to accelerate these local winds, also called ‘venturi’ or ‘gap winds’. If the approaching air-masses manage to pass the mountains blocking their way towards the Mediterranean, they often finally blast out to sea as a full-force storm. The most famous of these ‘katabatic’ and ‘jet-effect’ winds is the Gulf of Lyon’s ‘Mistral’. Once its cold and dry air streams down the Rhone Valley, Provence’s tourist beaches transform into challenging wave-spots in no time. The Mistral winds blow down to Sardinia in the Eastern Mediterranean and Minorca in the west and can occasionally reach all the way to Sicily, 1000km south. The ‘Tramontana’, Mistral’s little brother, is confined to the area between Montpellier and the Spanish border. Both Mistral and Tramontana winds are less common during the summer than the colder months of the year.

In contrast, the Strait of Gibraltar is a safe bet during the summer. This narrow Strait is less than 14km wide and can have nice jet-effect winds. Sometimes for days or even weeks at a time, the easterly ‘Levante’ whistles through between the southern edge of the Azores High and the North African heat low. Southerly winds predominate at most other spots along the Spanish Mediterranean coast due to the summertime land-based heat low.

Wind conditions differ in the Eastern Mediterranean. From May to September the barometric pressure steadily falls between the Azores Ridge in the west and the low in the Middle East. This low is not comparable to the cloudy low-pressure systems of the Westerly Wind Zone though. In part it’s a dry trough of the ‘Monsoon Low’ over India, but can also be a summer heat low with a centre over Southern Turkey. This pressure difference is a familiar Eastern Mediterranean feature, and thus the ‘Etesian’ blows dependably from the north. The differential is particularly large above the Aegean Sea due to the close proximity of the Turkish low. Hence the ‘Meltemi’ earns its reputation as a reliable wind from the Cyclades via Rhodes down to Karpathos.

Over on the Atlantic coastline of Western France and Spain, the Azores High takes control again – it’s no coincidence that the Bay of Biscay is full of surfers during the summer months. Whereas, local thermals and

topography enhance north-easterly winds in Galicia – if the Atlantic also builds up a nice swell you can expect very clean conditions. Similarly in Portugal; northerly winds prevail west of the Iberian heat low and wherever these are locally enhanced, spots such as Guincho or Sagres are busy. Morocco and the Canary Islands are especially blessed during the summer. Both are in the midst of the pressure gradient of the Subtropical High and the Equatorial Low and are treated with exceptionally stable north-easterly trade winds. Since these strengthen along Morocco‘s coastline and between the Islands, the wind conditions in Morocco and particularly on the Canaries are unarguably supreme between May and September.

The Azores High retreats out to the Atlantic Ocean for winter. In doing so, it also moves a few degrees

further south and allows troughs of low-pressure from the Westerly Wind Zone to bully their way into the Mediterranean. They squeeze in via the Strait of Gibraltar, accelerating the westerly ‘Poniente’ here. During wintertime the Mediterranean also produces its own lows that bring rain

and thunderstorms. These vivid lows repeatedly alternate with friendly highs. The Mistral and Tramontana now frequently assault the Gulf of Lyon, as does the brisk ‘Bora’ – a cold katabatic wind that blows stiffly off the Dalmatian coast. Overall, the Mediterranean wrestles the “Europe’s Stormiest...” title from the North Sea and the Bay of Biscay.

Spots on the Canary Islands, Morocco, and the Atlantic side of the Iberian Peninsula are treated to big wave sets during winter, though the winds are less predictable. The Azores’ effect on Portugal and Southern Spain is weakened, plus the trades head deeper south so have less influence on Morocco and the Canaries. So again, lows sweep in from the Atlantic to bring westerly winds and rainy weather.

As up north, Southern Europe – particularly its Atlantic Ocean and Western Mediterranean spots – provides a promising combination of

warm summers and vigorous winters. Best seasons for travel are spring and autumn – take some time and you’ve got a high chance of catching good wind and great waves at pleasant temperatures. Low prices and empty beaches are another clear off-season advantage.