The Five Main Jet Stream Blocking Configurations and Consequences of Abrupt Climate Change /Jun 22, 2020

With slowing, wavier jet streams (less zonal; more meridional waves) the likelihood of atmospheric blocks is much greater. As I explained from a boat in the middle of a lake in my recent CTV News interview, blocking explains Ottawa’s present heat wave and the unbelievable, unprecedented Siberian heat wave.  I explain five main blocking configurations:

• summer block (basic ridge);
• omega block;
• anti-cyclonic wave breaking block;
• cyclonic wave breaking block; and
• Rex block.

I chat about how blocking changes with rapid climate change acceleration, and how consequences of this change are bad news for humanity and society.

Ref: Blocking and its Response to Climate Change.  Link to download of PDF, here.  Woollings, Barriopedro, Methven, et al. Published: 20 July 2018

‘Atmospheric blocking events represent some of the most high-impact weather patterns in the mid-latitudes, yet they have often been a cause for concern in future climate projections. There has been low confidence in predicted future changes in blocking, despite relatively good agreement between climate models on a decline in blocking. This is due to the lack of a comprehensive theory of blocking and a pervasive underestimation of blocking occurrence by models. This paper reviews the state of knowledge regarding blocking under climate change, with the aim of providing an overview for those working in related fields‘.
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Jet Stream Fracturing and Blocking With Abrupt Climate Change // Jun 19, 2020

As the Arctic warms at faster rates, decreasing the temperature gradient to the equator, jet streams slow and become wavier in the North-South direction (aka meridional), making the likelihood of getting stuck for weeks on end in persistent patterns called blocks greater.

Westerly winds must reroute around these blocks, either to the north of them or to the south of them, or get stalled out completely. As the jet streams weaken and get more fractured, the temperature contrast between land and ocean gain influence, as does the topography (orography) of the land below (mountains versus flat regions). Complexity abounds.

Ref:  Extreme Weather, 12 June 2020:  Jet stream: Is climate change causing more ‘blocking’ weather events?   

‘Key to this unseasonable weather are persistent high-pressure “blocking” weather systems, which bring clear, dry conditions on the ground below for many days or weeks.

Blocking events bat away oncoming low-pressure systems that would bring the prospect of clouds and rain. They are particularly synonymous with heatwaves and drought in summer and bitterly cold conditions in winter‘.
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How the Ribbon of Fast Moving High Altitude Air is Vital to Understanding Weather and Climate ///Jun 19, 2020

Understanding the jet streams is crucial for understanding weather patterns throughout the seasons. Understanding jet stream changes from year to year is crucial for understanding climate change. Essentially, the jet stream acts as a wall between cold, dry high latitude air at the poles and warm, humid lower latitude air. As the Arctic warms at ever faster rates, the jet streams slow and become much wavier in the North-South direction, making the likelihood of getting stuck for weeks on end in persistent patterns called blocks greater. However changes in the tropics are also very important to jet stream behaviour.
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