Lightning

Lightning is a discharge of electricity due to the difference in electrical charges. One strike can superheat the air to 30,000°C, causing the surrounding air to expand and “explode.” This expansion creates a shock wave that turns into a booming sound wave, known as thunder.

Lightning is no stranger to Trinidad and Tobago as it accompanies thunderstorm activity in the region. Although most lightning occurs in the Wet Season across T&T, people can be struck at any time of year. Lightning strike-injuries and fatalities are rare in T&T, but all too frequently, strikes can damage property and cause power outages.

Content
Formation
Lightning Types

Cloud-to-ground
Cloud-to-cloud or Intra-cloud

Effects
Lightning Forecasting
Lightning Detection
Occurrence & Frequency In T&T
Lightning FAQ’s

Is it safe to hide under a tree during lightning or thunderstorm?
How many volts and watts are in lightning?
What color is lightning?
Can lightning strike the same place twice?

Formation

Ice crystals within a turbulent cumulonimbus cloud flow up and down in the cloud’s updraft and downdraft. During this movement, small charged particles (electrons) transfer onto the falling, larger ice particles (graupel) as these crystals crash past each other.

When the rising ice crystals collide with graupel, the ice crystals become positively charged and the graupel becomes negatively charged. (NOAA)
When the rising ice crystals collide with graupel, the ice crystals become positively charged and the graupel becomes negatively charged. (NOAA)

The transfer of charges separates the positive and negative charges, where the top of the cloud becomes positive (in 90% of cases) and the base of the cloud becomes negatively charged.

The upper part of the thunderstorm cloud becomes positively charged while the middle to lower part of the thunderstorm cloud becomes negatively charged. (NOAA)
The upper part of the thunderstorm cloud becomes positively charged while the middle to lower part of the thunderstorm cloud becomes negatively charged. (NOAA)

The ground is usually neutral, but anything above the ground tends to have a more positive charge at its top. Because opposites attract, the negative charge at the bottom of the storm cloud wants to link with the ground’s positive charge. Once the negative charge at the bottom of the cloud gets large enough, a negative charge flow, called a stepped leader, rushes toward the Earth. The positive charges at the ground are attracted to the stepped leader, so positive charge flows upward from the ground. When the stepped leader and the positive charge meet, a strong electric current carries the positive charge up into the cloud. This electric current is known as the return stroke. We see it as the bright flash of a lightning bolt.

Lightning Types

When the electrical charges become sufficiently separated in a thundercloud, with some regions acquiring a negative charge and others a positive, a discharge of lightning becomes likely. About one-third of lightning flashes travel from the cloud to the ground; most of these originate in negatively charged regions of the cloud.
(Encyclopædia Britannica, Inc.)
When the electrical charges become sufficiently separated in a thundercloud, with some regions acquiring a negative charge and others a positive, a discharge of lightning becomes likely. About one-third of lightning flashes travel from the cloud to the ground; most of these originate in negatively charged regions of the cloud. (Encyclopædia Britannica, Inc.)

Three primary types of lightning are defined by the “starting” and “ending” points of the lightning bolt.

Cloud-to-ground

Strong afternoon thunderstorms are producing frequent and dangerous cloud to ground lightning across parts of Trinidad. Photos: Kyle Fonrose (Gasparillo) https://ttweathercenter.com/thunderstorms/

Posted by Trinidad and Tobago Weather Center on Tuesday, September 8, 2020

The lightning strike originates from the cumulonimbus cloud and ends on the Earth’s surface. It can also occur in the reverse direction, which is called ground-to-cloud. This is the least common type of lightning but the most dangerous to those on the ground.

Most cloud-to-ground strikes are considered negative lightning strikes, where the negative charge from the cloud is transferred to the ground, with the electrons traveling along the lightning bolt (or channel). Positive cloud-to-ground lightning, which is even less common, occurs when a positive charge is transferred to the ground, making up, on average, 5% of all lightning strikes. However, positive cloud-to-ground strikes are considerably more dangerous, with double the peak current of a negative cloud-to-ground strike, making them more capable of property damage and fire ignition. Also, these strikes are capable of propagating further away from a thunderstorm.

Cloud-to-cloud or Intra-cloud

Intra-cloud lightning spotted from La Romain, Trinidad as thunderstorms approached Trinidad from the south and east on September 13th, 2018. (Jervis Jagroop)
Intra-cloud lightning spotted from La Romain, Trinidad as thunderstorms approached Trinidad from the south and east on September 13th, 2018. (Jervis Jagroop)

Most lightning that we see fall into these two categories. Cloud-to-cloud means lightning travels between two separate clouds, whereas intra-cloud means the lightning travels within the cloud. In both instances, the lightning bolt never reaches the ground, but it still produces thunder. Intra-cloud lightning is the most frequent type.

Cloud-to-cloud lightning spotted from Couva, looking towards a cluster of thunderstorms in the Gulf of Paria on September 12th, 2020. (Tarun Jagessar)
Cloud-to-cloud lightning spotted from Couva, looking towards a cluster of thunderstorms in the Gulf of Paria on September 12th, 2020. (Tarun Jagessar)

There are many, many other types of lightning. In T&T, we usually also see sheet lightning, which is cloud-to-cloud lightning that brightens the surface of a cloud, but the strike can’t be seen. This is typical for distant thunderstorms in our coastal waters and evening thunderstorms south of Trinidad moving across Venezuela.

Effects

Frequent lightning on October 13th, 2020 struck a coconut tree in Valsayn, setting it on fire. There were no reports of damage to nearby homes.
Frequent lightning on October 13th, 2020 struck a coconut tree in Valsayn, setting it on fire. There were no reports of damage to nearby homes.

Objects struck by lightning experience extreme heat and currents. When lightning strikes a tree, the heat can vaporize its sap, causing a steam explosion that bursts a tree’s trunk. In T&T, we also see dry branches on fire, particularly in tall palm and coconut trees.

Buildings or tall structures that are hit may also suffer damage, with holes burnt through the roof or concrete exploding, similar to that of a trunk of a tree.

The statue of Our Lady of Fatima at the Marian Shrine in Laventille was damaged by a lightning strike on Wednesday 9th September 2020. (Catholic News)
The statue of Our Lady of Fatima at the Marian Shrine in Laventille was damaged by a lightning strike on Wednesday 9th September 2020. (Catholic News)

Though 90% of people who are struck by lightning survive, humans, and animals that are struck may suffer severe injuries to their internal organs and nervous system.)

As mentioned above, thunder is the byproduct of lightning, due to the superheating of air surrounding the bolt with temperatures as hot as 30,000°C, which is five times hotter than the Sun.

The remains of a home at Oilfield Road, Union Village, after it was destroyed by fire on Tuesday. The cause of the fire was suspected to be lightning. (Ministry of Rural Development and Local Government)
The remains of a home at Oilfield Road, Union Village, after it was destroyed by fire on Tuesday. The cause of the fire was suspected to be lightning. (Ministry of Rural Development and Local Government)

The heated air expands explosively, creating a shockwave as the surrounding air is rapidly compressed. The air then contracts rapidly as it cools. This creates an initial crack sound, followed by rumbles as the column of air continues to vibrate.

Light travels at about 300,000,000 meters per second and sound travels through the air at about 343 meters per second. This is why we see lightning before we hear thunder, even if it is just above you.

Generally, for every three seconds between seeing a strike and when you hear thunder, it accounts for one kilometer. Lightning can be spotted up to 160 kilometers away, while thunder can only be heard from up to 32 kilometers away.

Lightning Forecasting

EMCWF Model forecast showing lightning density across Trinidad for 13th November 2020 (meteologix.com)
EMCWF Model forecast showing lightning density across Trinidad for 13th November 2020 (meteologix.com)

The presence of lightning is the differentiator between a normal convective shower and a thunderstorm. Hence, forecasting lightning and thunderstorms go hand in hand.

Forecasters rely on data and numerical weather prediction models that are run by supercomputers globally to determine whether conditions will be right to thunderstorm development.

Models are designed to calculate what the atmosphere may do at certain points over different spatial scales from the earth’s surface to the top of the atmosphere. Models use data gathered from weather balloons, satellites, aircraft, ships, temperature profilers, and surface weather stations.

The models start with these current weather observations and attempt to predict future weather using physics and dynamics to mathematically describe the atmosphere’s behavior. The predictions are usually output in text and graphics.

Lightning Detection

Ground-based lightning detector for Trinidad (privately owned) detecting frequent lightning from a strong thunderstorm southwest of Trinidad on August 5th, 2019.
Ground-based lightning detector for Trinidad (privately owned) detecting frequent lightning from a strong thunderstorm southwest of Trinidad on August 5th, 2019.

Lightning generates a wide range of electromagnetic radiation, including radio-frequency pulses. The times at which a pulse from a given lightning discharge arrives at several ground-based receivers can be used to locate the source of the discharge with a precision on the order of meters. There are several ground-based receivers, owned by the Trinidad and Tobago Meteorological Service and private citizens and businesses.

GOES-16 Geostationary Lightning Mapper (GLM) detecting frequent lightning associated with a strong thunderstorm across Northwestern and North-central Trinidad on October 13th, 2020. (Weathernerds.org)
GOES-16 Geostationary Lightning Mapper (GLM) detecting frequent lightning associated with a strong thunderstorm across Northwestern and North-central Trinidad on October 13th, 2020. (Weathernerds.org)

In addition to ground-based detectors, several instruments aboard satellites have been constructed to observe lightning distribution. Starting in 2016, the National Oceanic and Atmospheric Administration launched Geostationary Operational Environmental Satellite–R Series (GOES-R) weather satellites outfitted with Geostationary Lightning Mapper (GLM) instruments. These instruments are near-infrared optical transient detectors that can detect the momentary changes in an optical scene, indicating lightning. The lightning detection data can be converted into a real-time map of activity across the Western Hemisphere.

Occurrence & Frequency In T&T

Dangerous cloud-to-ground lightning spotted from Cunupia, Trinidad on 1st September, 2020 as strong thunderstorms affected the area.
Dangerous cloud-to-ground lightning spotted from Cunupia, Trinidad on 1st September 2020 as strong thunderstorms affected the area.

Lightning is not distributed equally across the globe. On Earth, the frequency is approximately 44 (±5) times per second, or nearly 1.4 billion flashes per year and the average duration is 0.2 seconds made up from a number of much shorter flashes (strokes) of around 60 to 70 microseconds.

The average areal extent of a singular thunderstorm is 1810 km2. Trinidad’s landmass is approximately 4,786 km2 while Tobago’s landmass is approximately 300 km2. This means that a singular thunderstorm can entirely cover Tobago or just under 4/10’s of Trinidad. Hence, it isn’t easy to pinpoint a particular area where lightning occurs most frequently. However, during the Wet Season, we see heat-driven thunderstorms favor western and northern halves of Trinidad, while tropical wave, ITCZ, and low-level trough triggered thunderstorms favor the eastern half of Trinidad and Tobago.

Lightning, as would be the same with thunderstorm activity, is a year-round phenomenon, though there is a higher frequency of thunderstorms during the Wet Season.

Lightning FAQ’s

Is it safe to hide under a tree during lightning or thunderstorm?

Definitely not! During a thunderstorm, strong winds can bring trees down easily. Lightning can also cause the tree to explode, causing you harm. The main things to know to keep safe:

  • NO PLACE outside is safe when thunderstorms are in the area!
  • If you hear thunder, lightning is close enough to strike you.
  • When you hear thunder, immediately move to safe shelter: a substantial building with electricity or plumbing or an enclosed, metal-topped vehicle with windows up.
  • Stay in safe shelter at least 30 minutes after you hear the last sound of thunder.
  • Do not take shelter under trees!

How many volts and watts are in lightning?

A strike can have 100 million to 1 billion volts, and contains billions of watts.

What color is lightning?

Strikes can appear to be many different colors depending on what the light travels through to get to your eyes. Haze, dust, moisture, raindrops, and any other particles in the atmosphere will affect the color by absorbing or diffracting a portion of the white light of lightning.

Can lightning strike the same place twice?

Lightning does hit the same spot (or almost the same spot) more than once, contrary to folk wisdom. It could be simply a statistical fluke (i.e., with all the strikes that occur, eventually it will hit somewhere near a previous strike within a short period). It could also be that something about the site makes it somewhat more likely to be struck.

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