What is the Pineapple Express?

As the Western US was pounded with snow, and resorts like Mammoth Mountain saw thirteen feet of snow, meteorologists were pointing to the "pineapple express." But what exactly does that mean? Meteorologist Joel Gratz fills us in.
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The western U.S. just experienced a six-day storm with over five FEET of snow falling in Colorado and between 6-13 FEET (yes, thirteen) falling in California, from Tahoe in the north to Mammoth in the south. Folks are throwing around the term “Pineapple Express” to explain this storm’s epic snowfall and rather warm temperatures, but that leaves many people scratching their heads trying to figure out what it all means (just like the double rainbow guy). So here’s the scoop.

The Pineapple Express is named after the state of Hawaii and their fruitful pineapple crop. In certain situations, the weather pattern sets up just right so that moisture is pulled from the area around the Hawaiian Islands directly toward the western U.S. In this case, we can even trace the moisture source well beyond Hawaii and all the way back to southeast Asia (see graphic).

While a six-day feed of moisture from Hawaii and beyond creates spectacularly high snowfall totals, it also delivers some abnormally warm air that makes for heavy, dense snow. The line that divided snow and “liquid snow” (I won’t dare use the “r” word) in Colorado held near 8,800ft during the main part of the storm on Monday, which is an extremely high elevation. The highest mountains of California, Utah, and Colorado did manage to avoid seeing liquid snow, though the high snow totals also masked the heft of the snow. I would be skeptical to hear any stories of people skiing “blower” powder during the main part of this storm; temperatures were just too warm to create truly fluffy snow, though skiing FEET of snow is never a negative experience.

With all the talk of La Nina this season, this storm was surprisingly not like a typical La Nina winter storm. With a southern jet stream feeding moisture from Hawaii (which is the southernmost point in the U.S.), the storm looked more like it belonged to an El Nino winter season. While this is surly an odd occurrence, it does appear that a more typical La Nina pattern of storms coming from the northwest should shape up toward New Years, which should also mean cooler temperatures.

Looking back on this storm, you might thank the pineapple express for big snow totals or hate it for bringing warm, dense snow. But you have to agree that this was an impressive six-day storm, the likes of which we may not see for many years to come.

Meteorologist Joel Gratz is the creator of Colorado Powder Forecast and is based in Boulder, CO.


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