‘Hurricane Hunter’ aircraft deploy to the PNW as a major atmospheric river takes aim at Seattle

This story was originally posted on MyNorthwest.com

The National Oceanic and Atmospheric Administration (NOAA) is sending its famous reconnaissance aircraft over a powerful storm system that threatens widespread flooding and damaging winds for Western Washington from Monday through Wednesday.

An atmospheric river barreling toward western Washington is powerful enough to warrant a rare deployment: NOAA is sending its hurricane hunter aircraft to fly directly over the storm system Monday, a dramatic move that underscores the impact of the incoming weather event.

During hurricane season, planes fly over hurricanes along the East Coast and Gulf Coast to collect vital data. Now, in the off-season, the plane is heading to the Pacific Northwest.

A special spy plane will cross the Pacific Ocean just off the coast of Washington throughout Monday, dropping instruments into the storm to collect real-time data that will help meteorologists refine their forecasts.

“Instead of sitting around doing nothing during the hurricane off-season, NOAA and the Air Force will sometimes send hurricane hunters here to fly over the big storms,” ​​meteorologist Scott Sistek, author. Emerald City weather BlogExplained. “By flying hurricane hunters over our storms, we can get a lot of real-time and verifiable data that we can feed into our computer models.”

That refined data is important as forecasters track a storm system that could drop three to five inches of rain on the Seattle metro area and push many rivers into major flood stage by Tuesday and Wednesday.

Two waves of storms hit on Monday

Ahead of heavy rain, storms will hit the region in two separate pulses on Monday, creating hazardous conditions for afternoon travel.

The first wave targets areas from Seattle south through Everett, with winds continuing around noon and into the late evening. Winds of 40-45 mph are expected across the region, with isolated gusts potentially reaching 50 mph.

“Usually when we get wind storms, we usually talk about the north, like the San Juan Islands, but it’s mostly the south,” Sistek said, noting the unusual wind pattern.

A second wind surge will occur as the storm passes, sending westerly winds across the Strait of Juan de Fuca. This post-frontal blast will hit Port Angeles, Sequim, Whidbey Island, and parts of western Snohomish and southwestern Skagit counties with sustained winds of 40-45 mph.

The dual wind events come on top of saturated soil from recent rains, raising concerns about trees falling onto power lines and roadways.

Major flooding is expected in western Washington rivers

The Snoqualmie River is at the most severe flood risk, with major flood conditions forecast through Tuesday near Carnation and Snoqualmie Falls. Residents in flood-prone areas of the Snoqualmie Valley should prepare to flood fields and cross roads.

The Skagit River is hovering within a fraction of an inch of major flood stage, with incoming flooding likely to push it over the threshold. Other rivers facing significant flooding include the Skykomis River in Monroe and the Cowlitz River in southwest Washington.

“I don’t think any river has ever reached flood stage without at least some kind of minor flooding,” Sistek warned. “For those other rivers, we’re not talking about historical flooding, but definitely flooding that you’ll notice and need to be careful about.”

It is expected that the water will accumulate on Tuesday and Wednesday and the impact of the flood will be high as the flow of the river increases.

See months worth of rain in Seattle days

The atmospheric river will dump three to five inches of rain on the Seattle area between Monday and Wednesday, roughly equal to the city’s average rainfall for the entire month of November or December, compressed into just three to five days.

“This is beyond normal Seattle rainfall,” Sistek emphasized. “Typically, a storm comes through, and it might be half an inch. Some of our strongest storms, maybe an inch of rain in a day. That’s more rain than we’ve ever had.”

The heaviest rain will be concentrated south of Seattle through Tacoma and the southern Cascades to Portland. While Whatcom County and other far northern areas will see substantial rainfall, extreme totals have shifted slightly south from earlier forecasts.

The storm has been downgraded to a Category 4, but is still dangerous

Forecasters have adjusted the atmospheric river’s classification from Category 5 to Category 4 on a five-point scale, although meteorologists warn it remains an exceptionally strong system.

“You’re playing semantics here. A 4 is still a very strong atmospheric river,” Sistek explained. “That’s just the standard they use to get to 5; it just dipped a little below that.”

Storm hunter data collected Monday could provide more accurate measurements that could adjust storm ratings or refine flood forecasts for specific river basins. Aircraft will drop instruments through storm systems, measuring conditions that satellites and scattered buoy reports cannot capture in detail.

Urban flooding, landslides also threaten riverine areas

Seattle residents who do not live near rivers still face significant risks from long, heavy rains.

Clogged storm drains can cause urban flooding in neighborhoods, while mountains and frost-laden bluffs can lead to landslides. Anyone living on or near slopes should monitor conditions closely and watch for signs of ground movement.

Highways are likely to be closed in areas prone to landslides. One area that often sees landslides is along West Valley Highway, a critical alternate route for commuters to deal with lane closures on Highway 167 in the Sumner, Pacific, and Auburn corridors.

What should be done now?

Meteorologists and emergency officials urge residents of Western Washington to take these steps:

Before the storm

• Clear gutters, downspouts, and storm drains of leaves and debris

• Secure outdoor furniture, trash cans, and other items that could fly

• Charge phones and electronic devices during power outages

• Stock flashlights, batteries, and emergency supplies

• Know your flood risk and evacuation routes

During the storm

• Never drive through standing water on the road

• Avoid unnecessary travel during high winds and rain Monday afternoon through Wednesday

• Stay away from electrical wires

• Monitor river levels if you live in flood-prone areas

• Look for landslide warning signs on the side of the mountain

The widespread impacts mark this as a significant two-to-five year weather event for the region, not the most extreme on record, but well above normal December rainfall.

Forecasters will continue to update forecasts through Monday as the seasonal river makes landfall and begins its wet, windy assault on the Pacific Northwest, with hurricane hunter aircraft giving meteorologists their most detailed look yet at the inner workings of a storm.

For the latest weather updates and river forecasts, follow meteorologist Scott Sistek at EmeraldCityWeather.com.

Charlie Harger is the host “Seattle Morning News” on KIRO Newsradio. You can read more of his stories and comments here. Follow Charlie In X And email him here.