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.
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