How do blocking highs form in the atmosphere

Blocking highs form when large-scale interactions between warm air, the jet stream, and feedback mechanisms in the atmosphere create a stationary or slow-moving region of high pressure. Typically, the formation involves a surge of warm air northward, which bends and bulges the jet stream. This bulge creates a ridge—an extended area of high pressure aloft.^[1][2]

Key Steps in Blocking High Formation

• Warm air advection: Warm air moves into the upper atmosphere, often triggered by shifting weather patterns or ocean–atmosphere interactions.^[1]
• Jet stream deformation: The influx of warm air causes the jet stream to buckle into a wavy (meridional) shape, rather than its usual straight west-to-east (zonal) flow.^[3][1]
• Feedback loop: The developing ridge of high pressure leads to sinking air, which further warms and stabilizes the region, reinforcing the block and its persistence.^[1]

Feedback and Persistence

Once established, blocking highs are maintained by a feedback loop—sinking air within the high-pressure zone keeps skies clear and dry, which allows more heating, further strengthening the high. The block distorts or slows the jet stream, causing weather systems to be deflected around or stall near the block.^[2][1]

Influence of Jet Stream Strength

A weaker or displaced jet stream makes it easier for high-pressure systems to become stationary, as the usual steering mechanisms are less effective. Occasionally, phenomena like sudden stratospheric warming or amplified planetary wave activity (Rossby waves) also contribute to the formation and maintenance of blocking highs.^[4][2]

Blocking highs are thus the result of complex interactions between atmospheric dynamics, large-scale waves, and surface-atmosphere feedbacks, creating persistent and impactful weather patterns.^[2][4][1]

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• https://www.koaa.com/weather/weather-science/how-blocking-high-pressure-systems-form-and-why-it-leads-to-snow-later-this-week      
• https://weather.metoffice.gov.uk/learn-about/weather/how-weather-works/high-and-low-pressure/blocks    
• https://www.climatesignals.org/climate-signals/atmospheric-blocking-increase 
• https://pmc.ncbi.nlm.nih.gov/articles/PMC6428232/  
• https://en.wikipedia.org/wiki/Block_(meteorology) 
• https://www.sciencedirect.com/topics/earth-and-planetary-sciences/atmospheric-blocking 
• http://www.bom.gov.au/climate/about/australian-climate-influences.shtml?bookmark=blockinghigh 
• https://ecn.ac.uk/what-we-do/education/tutorials-weather-climate/anticyclones-and-depressions/anticyclones/blocking-highs 
• https://opensnow.com/news/post/understanding-ridges-and-troughs