When the water cycle ramps up with an atmospheric river


PORTLAND, Ore. (KOIN) – The Pacific Northwest (PNW) is lucky to have a beautiful large ocean right next to us — you know, the Pacific Ocean.

The ocean is responsible for a large portion of our climate and it is responsible for plenty of the weather events that happen here. Why is the ocean so important? It is the source of one of our main steps to the water cycle – evaporation!

Weekend Meteorologist Joseph Dames

That’s a lot of water next to us and when the sun shines down on the ocean that energy will transform liquid water into the gaseous state of water vapor. That is the process of evaporation.

This is one of the main acts that occurs over the ocean. Why? There is a ton of water and plenty of sun.


Eventually water vapor changes back into liquid, forming clouds! This is the process of condensation.

Chief Meteorologist Natasha Stenbock

Well guess what happens next? The wind will then transport the moisture to other regions. One of the favorable regions is the PNW. We are always willing to accept some rain! Especially in the winter.

We have a few other tricks in our bag that can help us out too. We have the mountains, which can help encourage condensation that eventually leads to precipitation around here. Precipitation is an important process to the water cycle, as that water is then returned to the surface. That will find a way to rivers, lakes, storage under ground and eventually back to the ocean (cycle!).


That whole process is exaggerated during an atmospheric river as warm tropical moisture is transported to the Pacific Northwest, where it clashes with our colder mid-latitude region. When we find an abundance of moisture being transported across the Pacific Ocean, as we explain above, we will call this an atmospheric river.

Check out the slideshow below! These a few weather models/graphics that help show that stream of moisture.

That high volume of water can definitely lead to a high volume of concerns.

We know water can be very powerful. When it starts to come down in droves it may cause major disasters across the earth. We deal with those here in the PNW when we have big time rain events. The combination of the heavy rain and the terrain can lead to a vulnerable ground.

Sometimes that vulnerable waterlogged ground can give away! We call that a landslide. You can see in the photos below, that the earth (soil) breaks away and rapidly follows down a steep slope. This will create a very dangerous scenario that may include debris and mud.

These big rain events can cover a lot of ground! They can span hundreds of miles (over a day or two). Sometimes we have an abundance of rain from Canada all the way south to California, impacting multiple states and countries. In fact, one of those events just occurred here in the PNW at the end of January. The photo below is of a major highway that collapsed after a prolonged period of rain in California.

Don’t forget to watch the videos and you can don’t forget to partake in some of the experiments we have to offer. You can share your photos of your experiments with us too!

Big Sur Highway 1 Collapse January 28, 2021

If you’re interested in more, you can find part one of the water cycle weather kids lesson, which is found here.

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