This Pineapple Express was much juicier.
A strong Pacific weather system known as a Pineapple Express dumped massive amounts of rain in Snohomish County on Monday and is expected to create record flooding surpassing that of 1990, when the county’s rivers spilled over their banks.
“We’re expecting a bunch of rivers to set records and surpass numbers from 1990,” said Dana Felton, a meteorologist with the National Weather Service.
A Pineapple Express generally is a warm, wet air mass that originates near the Hawaiian Islands. It is a slow-moving weather system that can last for days.
The warmer the air mass, the more water it can hold, Felton said. Strong winds send the moist air slamming into the Cascade and Olympic mountains, where the water is “wrung out and is just like a hose,” Felton said.
The current storm is similar to the Pineapple Express that arrived on Nov. 8, 1990, and showered the county with 16.2 inches of rain over three days.
During that storm, snowmelt added 2 inches of runoff to the floodwaters, filling every stream and creek in the Skykomish River basin to capacity.
To make matters worse, a second warm front arrived 10 days later and dumped 9 more inches of rain overnight on the already waterlogged county.
That kind of rainfall usually happens only once every 25 years, Felton said.
This year’s Pineapple Express moved in Sunday afternoon. It dumped about 8 inches of rain around the county in 24 hours.
Up to 3 inches of rain were expected to fall overnight and this morning, adding to the flooding.
The rain is expected to taper off this afternoon.
“We don’t expect the rain to go away, but it won’t be raining nearly as hard,” Felton said.
Reporter Diana Hefley: 425-339-3463 or hefley@heraldnet.com.
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