Simply summarised, we are currently experiencing a midsummer situation, although it is not yet midsummer. It is mid-June, and on the calendar and astronomically, summer only starts with the summer solstice on 21 June at 4.57 pm. We don't talk about midsummer until July and August.
Even though we have always had such sunny and warm weather in May or June in the past, it is the general weather situation that is so unusual. Since the beginning of April, a high-pressure complex has built up in the haze around Europe that we haven't really got rid of yet. Since then, the high has always been somewhere else. It has constantly swung back and forth between Ireland, Iceland, Sweden and Finland. This meant that the North Sea and Baltic Sea areas were always on different sides of the high.
As the wind in the northern hemisphere always blows clockwise around a high, it sometimes came from the north-west and sometimes from the east. When we had a north-westerly wind at times and the North Sea was only 12 to 14 degrees, the air temperatures on the North Frisian Islands were only sufficient for a maximum of these temperatures. This still felt like autumn weather, when at the same time the Baltic sailors along the coast were already sailing in T-shirts and at over 20 degrees with offshore winds. Thanks to the strong sun, the air had enough time to warm up over land before reaching the Baltic Sea.
Unusual: midsummer weather even in early summer
When the high pressure system with its centre then moved eastwards from Ireland via Scotland towards Sweden, the Baltic Sea and North Sea were suddenly on its southern side and thus in an easterly wind. The air masses now came from the Baltic States and flowed over the Baltic Sea for a long time, which is now also a little warmer, but we didn't manage more than 21 to 23 degrees here between the Flensburg Fjord and the Bay of Lübeck to Rügen. In contrast, it reached 28 degrees on the Elbe and along the North Sea coast.
As a result, the strong temperature differences have changed once on the coastal side of northern Germany. And although it has been consistently sunny except for a few days with high fog-like clouds, the wind conditions have always been different. Once the high in the north had extended a little more towards Germany, the pressure contrasts were so low that it was mostly thermals and therefore sea winds that invited sailing close to the coast. But a short time later, the wind suddenly picked up a few strengths, but it was still sky-blue and cloud-free?
Strong winds out of the blue
The devil is usually in the detail without a significant change in the weather. And anyone who studies weather maps will also have seen that areas of low pressure from the Mediterranean have occasionally managed to move at least as far as Poland and eastern Germany. As these lows approached, the gradient (pressure contrast) on the Baltic Sea increased - and suddenly the wind was fresh to strong. In the afternoon, the wind strength increased again, in gusts even two on top, as the thermals were able to intensify the whole thing.
This resulted in a change in one weather parameter (wind) without the weather itself changing.
But if there are highs somewhere, and they last for weeks, lows have to appear elsewhere - and for at least as long. And this can also be seen in the recurring severe weather conditions in connection with lows in the Mediterranean region. Too much rain falls there in too short a time.
One man's high, another man's low
Under the highs, however, it is now not only bone dry, but the seas are also warming up considerably. Between Riga and Zealand, we are already seeing water that is four degrees warmer than usual at this time of year.
How much longer will this go on? For nature's sake, we can only hope that a change will come soon. And it looks like it will, at least temporarily. The highs are gradually losing their strength as the supply from the Azores High is cut off. An old low over Poland could still cause localised showers and thunderstorms in the unstable air mass at the weekend.
Weather changes during Kiel Week
A somewhat more widespread change in the weather is then on the cards for Tuesday 20 June to Thursday 22 June: A low pressure system near the British Isles will cause marginal lows to form over the Benelux countries and move towards the North and Baltic Seas. The systems coming from the south will bring additional hot air masses from southern Europe. Should the fronts of the lows then discharge, the air mass will harbour great potential for severe weather. Heavy showers, severe thunderstorms and gale-force gusts are possible.
At this point at the latest, you should prepare for this early on with rain and thunderstorm radar and keep a close eye on the situation. Once these lows have passed through, the weather models are already tending towards new highs in northern Europe and thus lows in the south. So it seems to be just a drop in the ocean, and after possibly some heavy downpours during Kiel Week, a new high pressure situation is likely to build up over Scandinavia and thus the North and Baltic Seas.
The premature midsummer thus seems set to continue - and with it the unusual weather situation with its regionally varying weather extremes.
The author
Sebastian Wache is a qualified meteorologist; he works as an expert in marine weather forecasting and professional weather routing as well as a cruising and regatta consultant at Wetterwelt GmbH in Kiel. He regularly passes on his knowledge to sailors in seminars and also presents the daily forecast for Schleswig-Holstein on NDR television together with Dr Meeno Schrader. Wache is a keen sailor himself and loves sailing on the North and Baltic Seas.
