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Lightning is one of nature's most spectacular phenomena, characterized by a massive electrical discharge that occurs between clouds, from a cloud to the air, or from a cloud to the ground.

This powerful event not only illuminates the sky but also poses significant risks, making its detection and monitoring crucial for public safety and various industries. In this blog entry, we take at what lightning is and how we monitor it. 

What is Lightning?

Lightning forms within storm clouds where strong internal winds, known as updraughts, propel tiny water droplets to the top of the cloud, turning them into ice. Some ice particles grow into hail, while others remain small. As hail falls through the cloud, it collides with smaller ice particles, transferring electrons and creating a negative charge in the hail and a positive charge in the ice particles. The updraughts continue to carry the positively charged ice particles upwards, while the negatively charged hail falls, creating a charge separation within the cloud.

The negative charge at the cloud's base attracts positive charges from other clouds and the ground. When the attraction is strong enough, electrons rapidly move towards the positive atoms, forming the lightning channel we see during a flash. This process can result in cloud-to-ground lightning, where electrons shoot down from the cloud at speeds of around 270,000 miles per hour.

Types of Lightning

Lightning can manifest in various forms, each with unique characteristics:

• Ball Lightning: A rare form where a luminous sphere is seen moving.
• Rocket Lightning: Slow-moving lightning perceptible to the eye.
• Pearl-necklace Lightning: Appears as a string of pearls due to brightness variations.
• Ribbon Lightning: Appears spread horizontally into parallel streaks due to strong winds.
• Forked Lightning: Features many luminous branches from the main channel.
• Sheet Lightning: Diffuse light with no visible main channel.
• Streak Lightning: Distinct main channel, often tortuous and branching.

READ MORE: What causes thunder and lightning?

Monitoring Lightning: The Met Office LEELA System

The Met Office employs the LEELA (Lightning Electromagnetic Emission Location by Arrival time difference) system to monitor lightning. LEELA is an automatic lightning location network consisting of ten sensors positioned across Europe. This system detects pulses of radio waves, known as 'sferics,' emitted during lightning strikes at a very low frequency (VLF). These sferics travel great distances, reflected between the Earth's surface and the ionosphere, similar to light in a fiber optic cable.

To pinpoint the exact location of thunderstorms, LEELA uses a network of sensors that detect sferics at slightly different times. Through a technique called multi-lateration, the system calculates the arrival time difference (ATD) of sferics at each sensor, determining the precise location of the lightning stroke.

READ MORE: Learn about lightning

Applications and Limitations of LEELA

LEELA data is invaluable for identifying hazardous weather associated with thunderstorms, such as intense precipitation, severe icing, wind shear, turbulence, and strong wind gusts. This information is crucial for public safety, aviation, and other industries. LEELA provides continuous lightning data in Met Office bulletins, 24 hours a day, 365 days a year.

However, LEELA has some limitations:

• It does not yet discriminate between different types of lightning (e.g., in-cloud or cloud-to-ground).
• Its accuracy and sensitivity diminish at longer ranges.
• It does not cover the entire globe, with areas like Far East Asia, Russia, South East Asia, Australia, mainland USA, and the Pacific typically out of range.
• LEELA only reports the time and location of lightning strokes, not their intensity, polarity, or other attributes.

Despite these limitations, LEELA is a significant advancement in lightning detection, offering twice the detection capability of its predecessor, ATDnet, with comparable accuracy.

READ MORE: Check out our live lightning strike map

Lightning is a fascinating natural phenomenon. Understanding its formation and characteristics is essential for appreciating its impact. The Met Office's LEELA system plays a crucial role in monitoring lightning, providing vital data to mitigate the risks associated with thunderstorms.

As technology advances, systems like LEELA will continue to enhance our ability to predict and respond to hazardous weather, ensuring greater safety and preparedness.

Keep up to date with weather warnings, and you can find the latest forecast on our website, on YouTube, by following us on X and Facebook, as well as on our mobile app which is available for iPhone from the App store and for Android from the Google Play store. 

About this blog

This is the official blog of the Met Office news team, intended to provide journalists and bloggers with the latest weather, climate science and business news, and information from the Met Office.