When you think of the weather in Hawaii, people usually picture visions of a tropical paradise with beautiful beaches as a warm breeze sways the palm trees amid infinite sunshine.
But Hawaii can bring rain, too, as people who live along the West Coast can attest to a few times every fall and winter.
There is a specific atmospheric river setup where the jet stream will dip to the south into the tropical Pacific Ocean near Hawaii, then gather a bunch of warm, moist air and carry it north and east across the rest of the ocean.
This train of moisture will then dump heavy rain where it reaches land, in either the Pacific Northwest or California.
What is a Pineapple Express?
Many locals call the weather event a Pineapple Express due to the storm’s Hawaiian origins and the Aloha State’s penchant for pineapples.
These storms can bring torrential rain for as long as 2 to 3 days and are well known for producing many flooding events.
The more significant Pineapple Express storms can carry as much as the equivalent of 10 to 15 inches of rain.
The accompanying warm air will also push snow levels far higher than average, perhaps as high as 6,000 to 8,000 feet in elevation, leaving all of the moisture to fall as rain in the mountains instead of snow and putting tremendous pressure on mountain-fed rivers and streams.
On the surface, Pineapple Express days are marked with unusual warmth, with temperatures reaching well into the 50s and sometimes the 60s in the Pacific Northwest when a high temperature in the 40s is typical.
Many record-high temperatures that occur in the fall and winter are set during dreary, rainy Pineapple Express events instead of the more logical sunny days.
The Pineapple Express is always considered an atmospheric river event, but not all atmospheric rivers are a Pineapple Express.
The source of tropical moisture must originate or pass near Hawaii to earn the name Pineapple Express.