Disaster - Thunderstorms


Thunderstorms consist of flashes of lightning followed by rumbles of thunder. In the Caribbean, they are usually accompanied by strong winds and heavy rain.

Thunderstorms are responsible for the development and formation of many severe weather phenomena.

How are thunderstorms formed?
Thunderstorms are formed by the upward movement of warm and humid air. When humid air rises, it cools and the moisture in the air will condense to form cumulonimbus clouds that can reach as high as 20 kilometres. The water in the clouds then changes from its gas form to liquid form and the drops get bigger. This is usually called the mature stage of the thunderstorm.

Types of thunderstorms
There are four main types of thunderstorms:

  1. Single Cell Thunderstorms: These have a lifespan of about 30 minutes and are not severe. The storms of this kind are rare and as these occur randomly, they are very difficult to forecast.
  2. Multi-cell Cluster Storm: This is the most common type of thunderstorm and occurs in a group. Storms of this kind can persist for a few hours and can produce moderate sized hail and weak tornadoes.
  3. Multi-cell Line Storm: This consists of a long line of thunderstorms that can produce hail the size of golf balls and weak tornadoes. Storms of these kinds can easily be predicted with the help of radar.
  4. Super-cell Storms: Although rare, these are highly organized thunderstorms. Storms of this kind pose a high threat to life and property as these can produce strong to violent tornadoes.

How are lightning and thunder produced?
Water droplets and ice crystals inside a cumulonimbus cloud will break up and become electrically charged. The upper portion of the cloud is positively charged while the middle and lower portions are negatively charged. When the electric voltage between the positive and negative charges is large enough, discharges take place and lightning is said to have occurred. Thunder is caused by the rapid expansion of the air surrounding the path of a lightning bolt. This expansion of air creates a sonic shock wave, similar to a sonic boom, which produces the sound of thunder. This sound is sometimes called a clap or crack.

Effects of thunderstorms
Lightning is a major threat during a thunderstorm and is quite deadly. Some of the dangers associated with thunderstorms are flash flooding, hail, strong winds and tornadoes.

Many people are killed each year by lightning and some victims do survive.

An individual struck by lightning may report a variety of long term symptoms which include memory loss, sleep disorders, depression, muscle spasms, stiffness in joints, fatigue, attention deficits, dizziness and an inability to sit for long.

You may have heard that lightning never strikes the same place twice. Well, this is just a myth. Lightning can strike several times in the same place.

Some lightning safety tips:

If you are outside:

  • Count the time between when you see a lightning flash and hear thunder. If the gap is less than 30 seconds, seek shelter. Try to get inside a building or hard topped car.
  • In a field, bend over and crouch. Do not lie down since wet ground can conduct electricity.
  • Do not stand under a large tree that stands alone.
  • Do not stand on a hilltop.
  • Get out of and move away from water bodies.
  • Do not carry or stay near metal objects.

If you are inside:

  • Unplug and stay away from electrical appliances including television.
  • Stay off the telephone.
  • Stay away from windows and doors.
  • Stay away from running water.

What to do after a Thunderstorm

  • Continue listening to local radio or television stations for updated information and instructions.
  • Watch out for fallen power lines and report them immediately.
  • Help someone who may require special assistance – infants, elderly people and individuals with disabilities.
  • Stay away from storm-damaged areas.
  • Report potential hazards.

What to do if someone is struck by lightning

  • Call for help. Get someone to dial 9-1-1 or your local Emergency Medical Services (EMS) number. Medical attention is needed as quickly as possible.
  • Give first aid. If breathing has stopped, begin rescue breathing. If the heart has stopped beating, a trained person should give CPR. If the person has a pulse and is breathing, look and care for other possible injuries.
  • Check for burns in two places – both where the person was struck and where the electricity left their body. Being struck by lightning can also cause nervous system damage, broken bones, and loss of hearing or eyesight. People struck by lightning carry no electrical charge that can shock other people, and they can be handled safely.