The Pineapple Express is a commonly used term for a West Coast phenomenon that results from atmospheric pressure.
Narrow regions in the atmosphere transport moisture from the tropics to northern latitudes in “atmospheric rivers” as part of the water cycle, but can therefore create flood risks.
The Pineapple Express, specificamente, is the “fiume” that runs from Hawaii to the U.S. and Canada’s west coasts, helping to provide the heavy rainfall and snow those regions are known for.
The system, which cools once it hits the continent, can result in five inches of rain in one day, secondo il NOAA.
The mix of high and low pressure centers over the Pacific makes the Pineapple Express one of the most potent of the “rivers” in the water cycle.
Despite the narrow band that the “fiume” flows over, the Express empties over a wide range of the West Coast, making it difficult to predict where the effects will hit.
A minor shift of the stream can create a wild difference between rain or snow, and where it actually makes landfall, secondo il Weather Network.