Europe’s weather blocking started in March

Posted: 18 August 2018

Incredible! Several months extraordinary summer from Great Britain to Finland!  Nowhere a clear explanation. Since spring, an expansive high-pressure ridge aloft has stretched across most of northern Europe, the reasons are not sufficiently explicated anywhere. Europe experienced a very dry spring and summer but the meteorological conditions causing it are hardly addressed. It was the hottest May-through-July on record in Europe reported the Washington Post  – August 18, 2018 ; reprint: sciencealert.  Billions and multi-billions have been invested in climatic research over the last several decades, and so little competence has emerged. Incredible!

Generously the MetOffice announced on 27th July 2018 : “We’re aiming to understand why the weather pattern this summer was so persistent, and to what extent this persistence may be influenced by human-induced climate change, as well as the role of global warming by greenhouse gases in raising the temperatures experienced in the heat wave. We’ll publish our findings later in the year.” Neither this post nor corresponding analyses in THE GUARDIAN (see an excerpt in the box) have much to say:

THE GUARDIAN

 Robin McKie;

 

Sun 22 Jul 2018

“The jet stream we are currently experiencing is extremely weak and, as a result, areas of atmospheric high pressure are lingering for long periods over the same place,” added Mitchell.
Other factors involved in creating the meteorological conditions that have brought such heat to the northern hemisphere include substantial changes to sea surface temperatures in the North Atlantic. “These are part of a phenomenon known as the Atlantic multidecadal oscillation,” said Professor Adam Scaife, of the Met Office.
“In fact, the situation is very like the one we had in 1976, when we had similar ocean temperatures in the Atlantic and an unchanging jet stream that left great areas of high pressure over many areas for long periods,” said Scaife.

The weather blocking started already in March

The major player in the event is certainly the lower than usual water temperatures in the mid latitudes of the North Atlantic, but without contributing regional sea water conditions across West and Northern Europe the record heat waves here and all over the Norther Hemisphere would not have happed – at least not in such an exceptional way. Weather blocking in Europe, north of the Alps, which prevents  the flow of low air pressure cyclones from the Atlantic via Central Europe to the East, require a substantial input by coastal  seas and particular the North and Baltic Sea.

After a mild winter, a cold spring was expected, we elaborated here on 26th February, as it follows:

[but] keep in mind that the current winter in Northern Europe had been extremely mild, to which shipping and the huge off-shore windfarms in the North- and Baltic Sea may have considerably contributed. The matter was thoroughly discussed in a paper-2016, and for example HERE. Any coffee stirred for too long gets cold. As soon as the reginal seas across Europe have lost too much of their heat stored during the summer season, cold air from Siberian can reach Europe and establish reign for days or weeks, respectively delay the arrival of spring. 

The subsequent post -17 March 2018 – states:

Europe’s Cold Spring – Man Made?
2nd Shivering in mid-March 2018

Extract: The last few days weather development support the thesis. Europe’s spring, respectively the months April, May and June are likely to show sub-temperature, as indicated in Fig. 1. Already forthcoming April the forecast indicates a significant negative anomaly (Fig. 2), with the North Sea and Baltics in focus. Why does it happen exactly in the regions? The explanation presumably stems from the various anthropogenic activities at sea.
Lengthy discussed HERE:

By two Addenda  [24. March] the question was raised: What do offshore wind farms contribute to the weather situation in April? A convincing answer would be a big bon for understanding climate, and how effective human activities at sea are to contribute to weather making and climate change”, and mentioned [on 01 April] that the: “Seasonal sea ice in the Baltic remained substantial below average. The peak was around the 10th March 2018, and is far away from the mean by the end of March.”

Presumably the principle conditions for an early spring and dry and hot summer was already laid since the cold air drop in from Siberia. Above normal air pressure ensures little cloudiness. Abundantly sunshine raises regional air temperature during daytime and dry-out the soil. High-pressure areas could establish more and more solidly over Northern Europe and deny cyclones and the jet-stream to travel unhindered eastwards, resulting in strong and lasting weather blocking. Atmospheric blocking alters normal climates across Europe and Russia by shifting low pressure tracks. In such a case cyclones and zonal wind pattern, e.g. known as the jet stream, deviates form a common pathway and reroute north and south of the anticyclone.

Weather blocking in Northern Europe is not uncommon, more in winter than in spring and summer, but well known; see:  Lukas Brunner, 2016. For example it happened during the first three war-winters 1939/40 to 1941/42, with strong weather blockings that wouldn’t had occurred without fierce naval war activities. Nowadays the regional seas in Europe are heavily used by shipping, fishing, off-shore wind farms etc. with a profound effect on the seawater structure that causes milder winters and colder springs, as analyzed in the paper: Northern Europe’s Mild Winters;  (in PDF). But nowhere the North- and Baltic Sea is even mentioned. The MetOffice is merely “aiming to understand why the weather pattern this summer was so persistent”. That is too little! That is incredible!

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