Post 30. July 2018 Below: Addendum A – 01 August 2018 – Too little understanding on what cause the weather blocking over N-Europe
What’s going on? Temperature exceeded more than 30°C North of the Polar Circle recently. Temperatures have soared over much of Europe over the last month, regularly exceeding 30°C and several temperature records have been broken. The conditions have been so extreme that wildfires have broken out in Sweden and the UK. Other continents either wonder about excessive heats. And what is causing this weather extreme? The most you can here is that it is a case of weather blocking, or the jet stream, the core of strong winds some kilometers above the Earth’s surface that blow west to east and move weather around the globe, which currently is looping to the north, but very weak, meaning the weather is staying in place. That describes a weather phenomenon, but not the reason why it is happening. But it is the way meteorology is talking about this extraordinary event. That is too little. A good explanation is pending.
Cold early spring.
Just as a reminder. After a modest winter 2017/18 in early spring the trend changed. Suddenly the news-press reported about an “arctic blast currently sweeping the country is to worsen over next week, warns Météo France, with some areas set to experience temperatures that feel as low as -25°C with wind chill. From Monday 26 February, the “Moscow-Paris glacial wave” from north-east Europe, which has already brought severe cold, is expected to bring lower temperatures still, and a wind chill that will make it feel even colder across the Hexagon. Mountain regions could feel as bitter as -25°C or below, and Paris is predicted to experience temperatures that feel as low as -13°C.”
How unusual is it that the May weather is as hot as it was this year in Sweden? Will this become commonplace in a changed climate? At SMHI, researchers and climatologists have analysed weather statistics and concluded that it was uncommonly warm and that it represented a record high which could remain unchallenged for a long time to come. (More HERE)
Iceland worst summer for 100 years
Iceland’s greyest, wettest summer since 1914 can be blamed on the UK heat wave, says Icelandic meteorologist Trausti Jonsson. “The people of Reykjavík are paying for the sunshine in England and southern Scandinavia,” said Jonsson, thanks to high pressure over western Europe changing the jet stream and pushing clouds over the north of the continent. (THE GUARDIAN)
July – Intense heat wave to bake western Europe
A hot July across much of Western Europe (AccuWeather, July 26, 2018) will climb to another level this week as a heat wave builds from Spain to Scandinavia. Some locations that may have their highest temperatures of the year this week include Madrid, Spain; Paris, France; Frankfurt, Germany; Amsterdam, Netherlands; and Stockholm, Sweden. While unseasonable heat is expected each day through this weekend, the hottest conditions are expected on Thursday and Friday.High temperatures will soar to or above 32 C (90 F) from the interior of Spain through much of France, Netherlands, Belgium and western Germany both days. High temperatures may reach 35 C (95 F) in Paris, Brussels and Cologne.Temperatures may reach 32 C (90 F) as far north as southern Sweden, including Stockholm.
Battle between LOW and HIGH
From the UK, across to Scandinavia and Japan, the hot weather is expected to continue for the rest of the month (July). Japan has just declared a natural disaster. Various temperature records for July were broken in southern California, eastern Canada, Algeria and Norway. Extreme temperatures led to public health warnings and even the temporary closure of Hanover airport as the thermometer hit highs of 36 degrees in some parts of Germany on Tuesday. So what is going on?
The indicated locations indicate that the jet-stream is not flowing across the North Atlantic straight from West to East, via Asia, Pacific and North America. That would be weather as usual. As the first image (above shows) the jet-stream is forced to the Arctic, blocked from moving rain and clouds in low-pressure formations across Central Europe eastwards, which is a result not the cause of more important weather phenomenon.
The path to identify the main mechanism to the current heatwave is the windy and wet weather in Island due to Low pressure and the lasting High pressure across Scandinavia. The two opposing pressure areas are responsible. Actually the most important factor is the High over Northern Europe, as that is the source which blocks the drifting of low pressure fields eastwards some call it west-wind-drift. A High pressure system to strive needs foremost cold air, low moisture, and a very dry landscape.
Unfortunately this does not explain the reason why the current High-pressure is so lasting and persistent in place. That is an urgent task for meteorology to find out. The current extreme blocking situation provides a chance to do what they failed to do in previous similar events. Until now they merely talk about global warming, sea-ice conditions, and Atlantic temperatures. Another important factor, the local and coastal seas from the Biscay to the Barents Sea, is largely ignored. For sure the Scandinavian High gets an immediate and substation support from the North Sea and Baltic Sea. We will amend this post if these regional matters are discussed by the weather services and climatology.
Too little understanding on what cause the weather blocking over N-Europe
Addendum A – 01 August 2018
The westerly circulation across Europe ceased since spring 2018 but meteorology does not know and does not discuss WHY? Although extreme blocking of the ‘west-wind-drift’ by an anticyclone (high pressure area) over Northern Europe emerge usually in winter such as 1683/84, 1739/40, 1794/95, 1829/30, 1894/95, 1916/17, 1941/42, February 1947 and 1962/63, but spring/summer blocking is possible. Although the phenomenon is known since long, the mechanism not. For sure the ingredients can and will be numerous, for example North Atlantic sea temperatures and sea ice conditions. But two principle conditions related to the strengths of a high pressure system over Northern Europe receive little attention, if any, namely dried-out conditions over parts of the continent and the sea-water conditions in the North Sea, Baltic Sea and the coastal seas from the Biscay to the Barents Sea. These two preconditions contribute to weather blocking in Northern Europe for sure. To know nothing about it, nor show interest to understand more about it, is unacceptable, when climate change matters are called the greatest threat man faces.
For a brief overview links to two Journal essays (2009 & 2017) and five recent news-paper reports are given here after.
2009 – Jana Sillmann et al: Present and future atmospheric blocking and its impact on European mean and extreme climate; https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2009GL038259
Excerpt: Atmospheric blocking plays an important role in the mid‐latitude climate variability and can be responsible for anomalous mean and/or extreme climate.
2017 – Lucas Brunner: Connecting Atmospheric Blocking to European Temperature Extremes in Spring; https://journals.ametsoc.org/doi/pdf/10.1175/JCLI-D-16-0518.1 pdf Excerpt: We found blocking in winter and early spring to be stronger connected to cold conditions
whereas blocking in late spring and summer is stronger connected to warm conditions.
….. blocking over central Europe is associated with warmer conditions, particularly from March onward
26. July 2018; July sees extreme weather with high impacts; https://public.wmo.int/en/media/news/july-sees-extreme-weather-high-impacts
Excerpt: The persistency of high temperatures in some regions – including northern Europe – has been due to a stationary high pressure system. ….
There is much scientific research into whether climate change and substantial changes to sea surface temperature, escalated by high multi-decadal natural variability, are contributing to more profound effect in altering the atmospheric circulation and so leading to more “blocking patterns.”
27. July 2018: MetOff/UK https://blog.metoffice.gov.uk/2018/07/27/summer-temperature-2018-the-new-normal/
Excerpt: The jet stream has weakened and got stuck to the north of the UK, with high
pressure settled over the UK and Europe. In the summer such a pattern leads to dry soils,
which means that if the sunny weather continues the energy of the sun is not used up in
evaporating water and the temperatures rise even more.
30. July 2018: July sees extreme weather with high impacts; https://www.finchannel.com/world/74869-july-sees-extreme-weather-with-high-impacts
Excerpt: Atmospheric blocking alters normal climates across Europe and Russia by shifting storm tracks. Typically associated with an anticyclone, the zonal wind pattern known as the jet stream deviates from its mean position and its westerly winds reroute north and south of the anticyclone.