The model precipitation forecasts for the next few days is extraordinarily unusual for late April, with some aspects unique for any time of the year.
We are talking about an amazingly long and wide precipitation/moisture band coming from the west that will bring record amounts to some locations from northern CA to southern WA.
Let me show you what I mean and be prepared to be impressed. I will start with the 24h precipitation ending 4 AM Monday from the UW WRF model (relatively coarse outer domain). I have never seen anything like this: a very wide band of precipitation stretching thousands of miles due east into the Pacific. The width of the precipitation band is extremely unusual (very wide).
Next, zooming in to the higher-resolution (12-km) domain for the 24h precipitation ending 5 PM Monday, one views a very wide precipitation band that is enhanced as it is forced to rise by the terrain in western Oregon and northern CA (1.28-2.56 inches indicated by the pink colors). I have been looking at these model runs for decades and have never seen anything like it.
Or how about the cumulative precipitation through Tuesday at 5 PM from the vaunted European Center model? The huge precipitation band is shown, with 2-3 inches from the Olympics to northern California. Want dry conditions? Head to the Columbia Basin.
The moisture coming into the Northwest is from a zonal (east-west) atmospheric river. During the winter, the most significant atmospheric rivers come from the southwest, but they tend to become more east-west during spring. One measure of an atmospheric river is the vertically integrated water vapor graphic, that shows the total moisture in a vertical moisture in a vertical column of air. The WRF forecast for 11 PM Sunday shows the high values (blue and reds) heading right towards the CA/OR border.
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How will Northwest Weather Change Under Global Warming? Help Us Determine the Local Impacts of Climate Change
Society needs to know the regional impacts of climate change and several of us at the UW are trying to provide this information with state-of-the-art high resolution climate modeling. With Federal funding unavailable, we are experimenting with a community funding to build this effort. If you want more information or are interested in helping, please go here. The full link is: https://uw.useed.net/projects/822/home All contributions to the UW are tax deductible.
We are talking about an amazingly long and wide precipitation/moisture band coming from the west that will bring record amounts to some locations from northern CA to southern WA.
Let me show you what I mean and be prepared to be impressed. I will start with the 24h precipitation ending 4 AM Monday from the UW WRF model (relatively coarse outer domain). I have never seen anything like this: a very wide band of precipitation stretching thousands of miles due east into the Pacific. The width of the precipitation band is extremely unusual (very wide).
Or how about the cumulative precipitation through Tuesday at 5 PM from the vaunted European Center model? The huge precipitation band is shown, with 2-3 inches from the Olympics to northern California. Want dry conditions? Head to the Columbia Basin.
To get an idea of how unusual this amount is, here is the % of normal for the above precipitation totals. Some locations are 400% of normal. But it is the north-south extend of the precipitation that really impresses me.
A forecast of atmospheric water vapor for 8 AM Monday shows the extraordinary east-west extend of the the water vapor plume, which originates over the southwest North Pacific.
You can see the ejection of the moisture from the tropics into the midlatitudes in this animation, which show the distribution of water vapor during the past few days (click on image if it doesn't animate). So the substantial rainfall we will be experiencing can be traced back, in part, from moisture starting over the Philippines.
The depressing fact: here in the Pacific Northwest we are living through a record-breaking wet winter and spring, and the action is not over yet. The good news: we should transition to an El Nino next winter, which should be associated with a different, and drier, atmospheric circulation.
_______________________
How will Northwest Weather Change Under Global Warming? Help Us Determine the Local Impacts of Climate Change
Society needs to know the regional impacts of climate change and several of us at the UW are trying to provide this information with state-of-the-art high resolution climate modeling. With Federal funding unavailable, we are experimenting with a community funding to build this effort. If you want more information or are interested in helping, please go here. The full link is: https://uw.useed.net/projects/822/home All contributions to the UW are tax deductible.
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