As well as the name of a popular stoner comedy, “Pineapple Express” refers to a particular meteorological phenomenon, a type of “atmospheric river”. We explore the true meaning of a so-called Pineapple Express.
Early reports of a ‘Pineapple Express’
You may have noticed recent reports of a “Pineapple Express” heading for Washington and Oregon starting this weekend.
Bringing with it the potential for avalanches and prolonged stretches of wet weather, the effects of a Pineapple Express can be severe.
But that doesn’t explain exactly what it is.
What is a Pineapple Express?
Basically, in weather conversations, Pineapple Express means a very large amount of warm rain, specifically in mid-latitudes.
Pineapple Express is a non-technical meteorological term. That means it’s a term actual meteorologists don’t use – instead, it’s more common for laypeople instead.
It refers to a phenomenon characterised by lots and lots of airborne moisture, usually occurring at mid-latitudes and traveling in narrow corridors.
Pineapple Express events involve a combination of moisture-laden air, hot-and-cold atmospheric dynamics, and the presence of mountains. Mountains cause airborne moisture to rise very quickly, cool and condense, before falling as rain.
Driven by the polar jet stream, these “atmospheric rivers” cause some of the most severe torrential rains along the western coast of North America.
Historical Pineapple Express events
Throughout the last few decades, there are frequent examples of severe cases of Pineapple Express events.
The most recent past event was in January 2021, when a powerful – and deadly – winter storm channelled a Pineapple Express into California for the last few days of the month.
Previously, in 1955, Northern California experienced the greatest flooding since the 1800s as a result of a series of Hawaiian storms.
Although contemporary reports of the 1955 Pineapple Express weather event didn’t use the term Pineapple Express, it has since been used to characterise it.
Latest reports of a Pineapple Express weather event
9news and CNN have both reported that a Pineapple Express event is due to strike parts of the United States’ west coast, namely Oregon and Washington, later this week.
The North West Avalanche Center has issued warnings of “very dangerous avalanche conditions”, with an “extreme” danger rating.
Meanwhile, the “other” meaning of the term Pineapple Express is not lost on some Twitter users.
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