Fox News Weather Center

What is a Pineapple Express?

As persistent, heavy rain swamps California, "pineapple express" has begun trending across numerous social media outlets.

"A pineapple express is a continuous surge of tropical moisture extending from near Hawaii all the way into a West Coast storm," Expert Meteorologist Bernie Rayno said.

The flow of tropical moisture must be directed into the storm and serve as energy, unleashing extreme amounts of rain over parts of the West.

The high rainfall totals often lead to major flooding, mudslides, road closures and travel delays.

Is a Pineapple Express Responsible for the Heavy Rain in California?

The storm bringing torrential rain to California is not that of pineapple express, Rayno explained.

While tropical moisture did contribute to this storm, it was not the main source. Most of the rain was fueled by a strong west-to-east jet that runs across the north-central Pacific Ocean.

Additionally, the storm has brought damaging winds from southern Oregon all the way down into Southern California. The winds have served as energy and are the true drivers of the storm, not the tropical moisture.

"Pineapple expresses are not known for wind, they're known for rain," Rayno said.

Additionally, satellite images of this storm reveal large masses of dry air around Hawaii that would not be seen in a true pineapple express setup.

"If this was a true pineapple connection, rainfall amounts would be double what we're seeing now," Rayno said.