Atmospheric rivers, thermal domes: Explaining extreme weather terms

BARRIE – Communities in southwestern BC are bracing for more rain forecast to hit the area on Tuesday, as a third atmospheric river moves in.

But what exactly are atmospheric rivers?

Here are some commonly used extreme weather terms.


According to the US National Oceanic and Atmospheric Administration (NOAA), atmospheric rivers are “relatively long, narrow regions of the atmosphere that – like rivers in the sky – transport most of the steam to the outside of the tropics”.

NOAA says these plumes move with weather systems, and can carry as much water vapor as the average flow at the mouth of the Mississippi River.

When they make landfall, water vapor is released in the form of rain or sometimes snow.

Though not always, NOAA says atmospheric rivers can “disrupt travel, trigger landslides, and cause severe loss of life and property.”

What’s more, a 2018 study led by researchers from NASA’s Jet Propulsion Laboratory found that as a result of climate change, atmospheric rivers may become slightly less frequent. , but will last longer and become more intense.


According to, heat inversion – also known as temperature inversion – occurs when warm air coats cool air in the lowest part of the atmosphere, known as the troposphere.

In a normal situation with no inversion, warm air is closest to the earth’s surface, with colder air at the top.

NOAA says the temperature inversion occurs because the air near the ground cools faster than the air “above”.

“This is most likely to happen when the sky is clear and the wind is light/calm,” the NOAA website reads. “Cooling will take place most easily in low places (such as a valley sheltered from the wind.)”

The problem, NOAA says, is that as warm air rises, cooler air under inversion cannot escape, meaning pollution and smoke get trapped.


According to the American Meteorological Society (AMS), a heat dome is a “special mass of hot air” that develops when high pressure in the air prevents warm air below from rising.

“So keep the air as if it were in a dome,” says AMS.

According to NOAA, heat domes occur when high-pressure atmospheric conditions combine with “effects from La Nina, creating giant heat zones that are trapped under the high-pressure dome.”

When heat domes are pushed up over land, they can cause heat waves.


A bomb storm, also known as bombogenesis, is a storm of rapid intensity.

Meteorologists use the millibar – the unit of measurement for air pressure in the measuring system – to measure atmospheric pressure.

According to NOAA, bombardment occurs when a “moderate tornado” rapidly strengthens, dropping at least 24 millibars in a 24-hour period.

This happens when a cold air mass collides with a warm air mass, “such as the air over warm seas,” the agency said.


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