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Lightning! What you should know!

Over the last few months, Trinidad and Tobago has experienced lightning events as observed in the image above. This image was captured by Ice photography on Friday 11th of September 2020 from Fanny Village, Point Fortin Trinidad. Although we are often fascinated by this beautiful but dangerous weather phenomenon that illuminates the sky, how much do we really know about ‘Lightning’?

Lightning is a luminous manifestation accompanying a sudden electrical discharge that takes place from or inside a cloud, or less often, from high structures on the ground or from mountains. When lightning strikes, it can heat the air through which it travels to an incredible 30, 000°C, which is 5 times hotter than the surface of the sun. This extreme heating causes the air to expand explosively, thus causing a shock wave that becomes a booming sound wave- called ‘thunder’ that travels outward in all directions from the flash. 

According to the World Meteorological Organization (WMO), there are three main types of lightning that can be distinguished: 

  • Cloud to Air Discharge
  • Cloud to Cloud Discharge
  • Cloud to Ground Discharge 

The image above demonstrates a thunderstorm cloud and the three different types of lightning discharge. 

Cloud to Air Discharge

Lightning by air discharge is sometimes called “streak lightning”, which occurs as sinuous discharges passing from a thundercloud to the air and not striking the ground. The discharge often divides into branches but with a distinct main channel. It frequently includes a long quasi-horizontal part.

Cloud to Air Lightning photo taken by Ice Photography 

Cloud to Cloud Discharge 

Lightning that is cloud discharged is popularly called “sheet lightning” because it lights up the sky with a sheet of light, occurs within the thundercloud (intra-cloud lightning), or from one cloud to another (cloud-to-cloud lightning or inter-cloud lightning). It typically creates a diffuse illumination without a distinct channel being seen. This type of lightning includes the so-called heat lightning, consisting of diffuse light flashed from distant thunderstorms seen at the horizon. Sometimes lightning discharges originating below or within the anvil can be seen to move horizontally for some distance, generating multiple tree-like branches. These are known as “anvil crawlers”.

Cloud to Cloud Lightning photo was taken by Adrian Bernard

Cloud to Ground Discharge

Ground discharge is a type of lightning, popularly called a “thunderbolt” or “cloud-to-ground lightning” because it occurs between clouds and the ground. It typically follows a tortuous course and is usually branched downward from a distinct main channel which may appear as a streak, forked or ribbon lightning.

A ground discharge is initiated when a downward-moving, negatively charged stepped leader connects with a streamer of positive charge reaching upwards. Once this electrically conductive channel is established, a massive electrical discharge follows. This is the “return stroke” and is the most luminous and noticeable part of the lightning discharge. Most cloud-to-ground lightning flashes are made of several strokes, thus causing a flickering or strobe-light effect.

Ground-to-cloud discharges initiated by an upward-moving leader can sometimes originate from objects on the ground, such as tall towers and skyscrapers.

Cloud to Ground Photo taken by Krishna Ingraham II

As mentioned above, lightning strikes can heat the air around it to 30, 000°C. Lightning strikes pose a serious threat to human life and property. Each year some 25 million cloud-to-ground lightning discharges occur in the United States alone, killing more people than tornadoes and hurricanes. 

There are many myths about lightning, one of the most popular is, lightning does not strike the same place twice; however, lightning often strikes the same place repeatedly, especially if it’s a tall, pointy, isolated object. The Empire State Building is hit an average of 23 times a year. 

Lightning is extremely dangerous. When lightning strikes the ground it seeks out the shortest route to something with a positive charge, this might be a tree, a tall building or a person. There is a 30- 30 rule- if time between flash and thunder is less than 30 seconds, go inside! And wait 30 minutes after the last observed flash to resume outdoor activities. 

As lightning strikes are so dangerous, it is very important for the public to be aware of impending strikes. Meteorologists utilize their skills and analysis of meteorological data to forecast thunderstorms which produce lightning. Lightning can be observed/reported using the human eye, satellite imagery and even Automated Weather Observing Systems (AWOS). 

The image above was taken from the TTMS Automated Weather Observing System (AWOS). 

The Trinidad and Tobago Meteorological Division installed this Automatic Weather Observing System in November 2016. It has Meteorological Sensors inside the Piarco International Airport, along the Runway and consists of Low- Level Wind Shear Alert System (LLWAS) sites located on the outside around the Aerodrome. Near the End of Runway 28, (on the Eastern end of the Runway at Piarco Airport) Vaisala Meteorological Sensor Lightning Detector TSS928 is installed. This valuable lightning detector allows the TTMS to produce images like the one above and alerts the Meteorologist to important information such as the direction and distance of a lightning strike.

To learn about lightning safety, click here! 


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