Mid-Island residents are used to being battered by a variety of storms each year, but what do the different weather terms mean exactly? (The Canadian Press)

By Jordan Davidson

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Showers, rain and atmospheric rivers: explaining West Coast weather

Jan 9, 2023 | 5:33 AM

NANAIMO — Significant rainfall over the weekend is set to continue through the week.

It’s another parade of storms coming in from the Pacific, with an increasingly more familiar array of terms being used to describe them from rain to atmospheric rivers.

Derek Lee, meteorologist with Environment Canada, said when it comes to differences between showers, periods of rain, or atmospheric rivers, it all depends on the amount of precipitation and where it originates from.

“Rain is usually brought by a more organized system, usually systems from the Pacific will bring a large amount of rain that can precipitate in one area and it’s usually a day event and then it moves off.”

Showers are obviously lighter which will mostly come from systems which are less structured with precipitation falling over a longer period of time.

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Atmospheric rivers, also known as Pineapple Express storms, come from streams of moisture out of the tropics, with the naturally warmer air containing higher amounts of water vapour.

Infamously, a series of rivers devestated parts of B.C. in 2021, closing highways and opening sinkholes.

Meteorologists started using the term atmospheric river, a term coined in the early 1990’s, instead because people would assume a ‘Pineapple Express’ originated from Hawaii, which isn’t always the case.

“It’s usually that stream of moisture challenging from the tropics all the way up into the Pacific Northwest, and that’s what brings us some of our heavier rain events,” said Lee.

California was hit by three ‘Pineapple Express’ atmospheric river winter storms in a row to start January, bringing high winds and intense rains to the coastal state.

Lee said those storm systems can vary in size, intensity and duration every time they form making their projected path difficult to predict.

“Atmospheric rivers can sometimes be beneficial if it’s not too heavy of rain, and it also can be disastrous, similar to what we saw last year. As always, heavy rain, in general, can bring hazards at any time, but atmospheric rivers do have the capability of bringing more moisture and warmer temperatures for us.”

Environment Canada is calling for steady precipitation beginning mid-week, after a Pacific wind storm brings strong winds and rain beginning Monday, Jan. 9.

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jordan@nanaimonewsnow.com

On Twitter: @JordanDHeyNow