Dee Hartin took this photo of the thunderstorm at Casino on Tuesday, November 12.
Dee Hartin took this photo of the thunderstorm at Casino on Tuesday, November 12. Dee Hartin

Anatomy of a storm. Everything you've always wanted to know

SO WHAT the hell are storms and how do they form?

We all know that thunder and lightning, heavy rain, hail, and dangerous winds are created by these nasty little weather patterns, but we usually leave the science up to our trusty meteorologists.

For those who are curious, however, we've put a little time into boiling down storms into a few basics.

A storm's engine

Storms rely on a few things to get going: just like a car, they need fuel, an engine, and a spark.

The fuel for a storm is warm and moist air. That's why storms are most frequent here during the spring and summer months, when the sun is able to rapidly heat up the earth during the morning.

Heat rises and it absorbs moisture, so that heat on the ground ends up heating the air and heading up into the atmosphere along with the water vapour it collects on the way.

This "updraft" is the first stage of a storm - the formation of rising, increasingly massive and vertically billowing clouds.

It's actually just like the formation of normal clouds, but on a grander scale.

In a severe storm, the updraft is magnified by cold air in the upper atmosphere, which enables the hot air which started on the ground to continuously rise higher and higher, which is visible in the formation of huge, rising clouds.

This is aided by the approach of a cold front, or more typically on the North Coast, a low pressure trough. This is the "kicker" that turbo boosts the updraft.

The faster the updraft, the more powerful is the potential storm. That's because it simply has more energy. It's picking up plenty of water and heat from the ground, which is stored energy, and sending it skyward.

Later, it will release that energy and dump it back on the earth. Think, rain, hail, wind, and lighting as a by-product (we'll get to that).

 

Storm building over Coraki
Storm building over Coraki Samantha Elley

 

What then creates a "severe" storm is an unstable upper atmosphere, and you might think of it as the engine of the storm.

Severe storms will produce one of the following.

-          Hailstones with a diameter of 2cm or more.

-          Wind gusts of 90kmh or greater

-          Flash flooding

-          Tornadoes

Strong winds in the upper atmosphere set up the structure for a severe storm, because they fan out the top layer of the storm cloud, so when it finally bursts into rain and hail, it doesn't kill the updraft. If it did, that would just be a one-off storm.

This high wind shear allows a continuous updraft in one area, and a downdraft (the storm) in another as the storm moves across the region.

A high wind shear is also necessary for the formation of clusters of storms, or multi-cell storms, which are basically a chain of storms across the landscape.

Lismore storm as it rolls over the airport.
Lismore storm as it rolls over the airport. Craig Rose

Get Nasty: Supercells.

Supercells can be thought of as "perfect" storms.

They are some of the most dangerous weather events we can experience.

They have all the hallmarks of a storm described above in such perfect alignment that the storm is self-contained system and does not dissipate, despite its raging release of energy, but continues for hours. It literally has a "mind of its own".

Hail

Hail is just rain which is frozen at the incredibly high altitudes that a storm clouds peaks reach into the sky, which are as cold as -60C.

It is sent on a rollercoast ride in the updrafts and downdrafts of the storm cloud.

As it travels like this it picks up more and more water which becomes ice and gets bigger and bigger before it finally falls out of the sky.

The stronger the storm, the more it can sustain larger hailstones.

Lightning

Lightning is a massive discharge of static electricity.

There's positive electrical charges at the peak of a storm cloud, negative charges at the base, and positive charges at the base.

When there's enough of these, a tipping point is reached and lighting breaks out.

Lightning strikes near Ballina. Photo Contributed Scott Rolph Early Bird Photography
Lightning strikes near Ballina. Photo Contributed Scott Rolph Early Bird Photography Scott Rolph

What to look out for on a likely day for a severe storm:

A warm, slightly humid, still morning is often ideal for thunderstorm development on the North Coast.

This will heat the earth and provide plenty of moisture for the storm.

A severe thunderstorm requires one more thing: an approaching cold front or low pressure trough to exacerbate the upward movement of that energy.

"When surface heating reaches a critical point, or the layer is otherwise weakened, sudden and explosive cloud development can occur. Thunderstorms which break out in this abrupt fashion are more likely to be severe because all the day's ingredients and energy are available for an immediate, concentrated release," the Bureau of Meterology explains.

Storms in NSW

  • There's between 60 to 150 severe storms in NSW each year
  • Thunderstorms are most common in summer across the state, but on the North Coast in spring and early summer.
  • They are most common between 2pm and 6pm.

A few facts you might like outsmart your friends with:

  • There's about 45,000 storms a day across the globe. Only a small percentage are considered severe.
  • Each one contains more than 10 times the energy of the atomic bomb dropped on Hiroshima.
  • A storm cloud can accumulate 500,000 tonnes of water.
  •  A lightning bolt contains several hundred million volts of electricity, and is five times the heat of the surface of the sun, or 27,000 degrees Celsius.

Thunder is the sound of the air in the lightning channel expanding or "bursting" in the extreme heat



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