Hailstorms, remarkable meteorological occurrences characterised by their frozen intensity and destructive potency, inspire awe. But have you ever wondered how these frozen pellets form? In this blog, we will explore the science behind the creation of hailstorms and the process behind them.
Source: Bureau of Meteorology (BOM), 24 May 2018
According to the Bureau of Meteorology, "Hailstones are clumps of layered ice that form in updraughts, the rising air within thunderstorms."
Section 1: The Birth of a Hailstorm: The Essentials
Understanding Different Layers: Hailstorms originate inside thunderstorms that have different layers of air with varying temperatures. These layers are crucial in the formation of hail creating the requisite conditions for the development of ice pellets
Updraughts and Super-cooled Water: Thunderstorm updraughts (rising air) elevate raindrops to freezing upper atmospheric layers where they come into contact with 'super-cooled' water droplets. This means they're colder than 0 °C, but still liquid. Despite subfreezing temperatures, these particles remain in a liquid state due to the absence of nuclei for crystallization.
Hailstone Formation: The impact of raindrops upon super-cooled aqueous particles results in freezing. As updraughts carry the frozen particles higher within the storm, further encounters with supercooled water lead to the accumulation of layered ice.
When raindrops hit these super-cold water droplets, they freeze. Updraughts then carry these frozen bits higher within the storm, where they encounter more super-cold water and grow into layered ice.
Section 2: The Role of Updraughts and Downdraughts
Reinforcing the Core: Growing hailstones are transported vertically within the storm through the combined action of updraughts and downdraughts, leading to the accumulation of additional ice layers. This process, termed accretion, results in the progressive enlargement of hailstones during each cycle.
Influence of Wind Shear: Wind shear, the variation in wind speed and direction with altitude, also contributes to hailstone growth. Strong wind shear creates horizontal rolling motions within the storm, causing hailstones to collide and amalgamate, further increasing their size.
Section 3: Unleashing the Fury of the Hailstorm
Maximum Dimensions and Gravitational Force: As hailstones attain a mass exceeding the capacity of the storm's updraughts, their descent commences. The velocity of descent escalates with the size of hailstones due to their mass. The unleashed ferocity of a hailstorm stems from the plummeting of these ice pellets to the ground, inducing chaos and potential destruction.
The science behind hailstorm formation is a captivating testament to the intricacies of our atmosphere. As property owners, understanding the birth of a hailstorm can help us appreciate the forces of nature at play. With this knowledge, we're better equipped to prepare for the unpredictable, safeguard our properties, and stay safe in the face of these meteorological wonders.
Source: Bureau of Meteorology, 24May 2018 https://media.bom.gov.au/social/blog/1733/explainer-how-does-hail-form/