The Pacific Northwest encounters a second destructive atmospheric river in a week

The blue color shows that the moisture plume predicted this weekend will reach the Pacific Northwest, the second of three atmospheric river incidents that hit the area in a week.
GIF: Earth Wind Diagram

The Pacific Northwest is still affected Catastrophic flood Affected by the heavy rain last week. But residents already need to prepare for the next round of disasters.

An atmospheric river is preparing to bring double-digit rainfall again, drawing water from the depths of the tropics and washing it up the coasts of British Columbia and Washington. The increased rainfall may cause some places to experience the wettest November on record, and cause suffering to areas that are still recovering from last week’s floods.

Atmospheric River arrives on Wednesday

A stream of moisture drains from Hawaii to the northwest, making it a classic pineapple express atmospheric river.When the tide approaches the coast, it shoots out the gaps between the high pressures System to the south and low pressure The system faces north.Those will be like one Kettle Machine, Basically a slingshot on an atmospheric river in British Columbia on Wednesday night.

The first drop of water will hit Thanksgiving travelers on the U.S. border in time.However, this trickle will intensify and turn into a torrent on Thursday.. Storms can bring up to 6 inches (15 cm) of rain to coastal areas and cause wind speeds of up to 40 mph (64 km/h). The National Weather Service and its Canadian counterpart, Environment Canada, issued various flood and wind warnings for the storm.

A zoomed out satellite view of total precipitation, a measure of atmospheric humidity, showing the tongue of moisture from Hawaii to the Pacific Northwest.

This is the first of many atmospheric rivers

After the first wave of moisture will be a series of others. After the rain gradually weakened on Friday, another system will land on Saturday and continue until Sunday. Then, it might rain again on Monday because the NWS warned that this could be the “third system that may last longer,” keeping the weather wet and underwater until Wednesday. All in all, when this event occurs, as much as 20 inches (51 cm) of rain may fall.

Rating created by a group of scientists Western Weather and Water Extreme Events Center And other agencies that simulate the scale of Hurricane Saffir Simpson indicate that this series of storms may reach the peak of a Category 4 atmospheric river off the coast of British Columbia. The scale factor of intensity and duration and Category 4 indicate that this is a severe storm. At the same time, Washington will “only” need to deal with two types of atmospheric rivers.

Flooding becomes a problem again

The atmospheric rivers hit British Columbia particularly hard last week. At one point, every road connecting Vancouver and the rest of Canada was closed due to mudslides caused by heavy rain. A series of storms this week may bring a whole new wave of mudslides.

Even if the rainfall is not as strong as last week, there are three factors that may increase the risk of flooding. First, the soil is still saturated with the storm last week. This means more runoff. The wildfires this summer increased the runoff problem. The monster fire that swept through British Columbia destroyed the vegetation that fixed the soil, Turn the slope into a veritable landslide’N SlideshowThis led to a huge mudslide last week, and this storm may have the same consequences. Moist, loose soil also means that the wind can easily knock down trees and dead wood, adding another danger.

The third factor is that the snow on the mountain has increased since the last storm. However, as weather network meteorologist Tyle Hamilton Point out in the video, During the second atmospheric river, the icing level will rise, This means that rain may fall on the snow. This will add more water to the ground, which is why it is important to heed travel warnings, even if it means having to spend an extra day with your in-laws.

The big picture: La Niña and climate change

This is the rainy season in the west. Even so, Jacob DeFlic, a meteorologist at the Seattle office of the National Weather Service, told Capital Weather Gang that it is quite unusual to see so many atmospheric rivers “so early in the season.”

Several factors may have contributed to a vigorous start.the first is La Niña phenomenon formed last monthThe characteristic of this natural climate phenomenon is that the sea temperature in the eastern tropical Pacific is lower than normal. in turn, Affect weather patterns around the world. This includes the Pacific Northwest, where the La Niña phenomenon increases the chance of wetter conditions.

Then there is climate change. Every 1.8 degree Fahrenheit (1 degree Celsius) increase, The atmosphere can hold 7% more water. There is a formula to describe this simple relationship, is called Clausius Clapeyron equation. (This is an interesting Bankruptcy At the Thanksgiving table. ) This means that atmospheric rivers are more humid than before.A sort of Learn However, a study published in “Nature Climate Change” last month found that industrial pollution inhibited atmospheric rivers and basically caused the impasse between 1920 and 2005.

However, this balance is beginning to shift, and with the impact of climate change, this balance will continue to occur in the coming decades Greater control leads to more intense atmospheric rivers.with More intense wildfire season As the temperature rises, this also means that more rainfall will have more Overturning an unstoppable slope disaster.

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