The heavy rainfall is over, but some rivers are still rising. The most impactful atmospheric river event of the past few decades.
Consider the 5-day rainfall totals below, and be prepared to be impressed.
Many of the windward slopes of the Cascades and Olympics received more than 10 inches, with some experiencing 15-17 inches.
You will also notice extreme rain shadow areas in the lee (east) of major barriers, which received less than an inch.
Numerical weather prediction models were STUNNINGLY good, as shown by the predicted 5-day precipitation totals by the UW WRF model made last Sunday (see below).
Close correspondence between predicted and observed rainfall.
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The problem is that governments, local agencies, and others are not sufficiently taking advantage of these skillful forecasts to save lives and property. The media do not understand the profound impact of improved weather prediction technology.
This problem is compounded by the National Weather Service, whose forecasts and warnings have declined substantially compared to the state of the art.
I can provide a half-dozen cases of the NWS failing to provide timely warnings even when model forecasts are excellent, such as this event and the Seattle ice storm of December 2022.
I hate to reveal this, but ANOTHER significant atmospheric river/precipitation event is in the forecast.
Consider the predicted 72-h precipitation total ending 4 AM on Thursday. Yikes...pretty wet, with some mountain areas getting 10 inches. This is problematic, falling on saturated soils and rivers already well above normal.
To address the reliability of this forecast, one should consult ensembles of many forecasts. Below are plots of forecast precipitation at Stampede Pass in the central Cascades from many forecasts.
All are going for a major precipitation event starting in the middle of next week. You can take this to the bank.
All of this is a reminder that the most impactful severe weather of the Pacific Northwest is flooding. Not heatwaves, not wildfires, not windstorms.
All of this is a reminder that the most impactful severe weather of the Pacific Northwest is flooding. Not heatwaves, not wildfires, not windstorms.
What are your thoughts on the research which suggests that global warming will increase the frequency and severity of atmospheric rivers on the West Coast ?
ReplyDeleteCliff addressed this on the radio yesterday. Basically sounds like the small rise in temperature over the last 100 years has little to no affect on frequency. There is a slight increase in rainfall from the air being able to hold a little more moisture, but the overall impact seems quite low.
DeleteIn B.C. we were hit hard by a very similar event in 2021. The last 5 years have felt exceptionally volatile regarding extreme events throughout the year…. record floods, record fires, droughts, record heat, record cold. Can’t help but feel this is the new normal unless there is another X factor to account for so many over such a short period.
DeleteI share your feelings about the increase in extreme weather events. We've sure had a bunch of them in recent years, and I do worry that this increased frequency of such events is already becoming normal. It sounds like B.C. was also hit pretty hard by this week's atmospheric river. I hope everyone up there is doing okay.
DeleteI was more interested in projected future impacts than present effect. Higgins et al. (2025), for example, predicts that there will be a nearly order of magnitude increase in what have historically been 100 year storms with 2 degrees C of warming. That is what we would now call a "100 year storm" will occur nearly every 10 years.
DeleteAnother significant feature of this wet weather pattern was the "Chinook" warm wind that hit the lower east slopes of the Cascades Wednesday evening. The temperatures in the lower Wenatchee valley jumped from the upper 40s to the upper 60s and lows 70s and held through much of the evening hours. Unfortunately the temperature readings from the Wenatchee Tree Fruit Research Center were missing during the warmest period and did not catch the warmest temperatures which were close to 70, and would be a record high for December.
ReplyDeleteIn Cashmere, my partner and I sat out on our back patio with a glass of wine in the pitch dark (power outage) like it was a nice June evening. It definitely was an experience.
DeleteNot exactly the weather you'd expect over there in December!
DeleteEarly today, Leavenworth WA was hit with sustained, catastrophic winds, along with major flooding. The city is without power and many Western Chelan County locations look like a war zone. Why was this not predicted so residents could prepare for this kind of serious emergency?
ReplyDeleteI worry that we'll not get enough mountain snow to allow for Yakima Valley farming. It's just too darn warm.
ReplyDeleteAt least snow levels are supposed to start dropping by Tuesday - that should reduce the areas contributing to insane runoff amounts.
ReplyDeleteThere is a touch of survivor's guilt that can be had with this. So many areas that were hard hit in near proximity, and yet that uber rain shadow even resulted in actual SUN for a sizable portion of this event in the central sound. Some parts of Kitsap are even at a deficit for where rainfall should be for this month.
ReplyDeleteSeems like some though needs to be considered on better managing the rivers at flood stage. More reservoirs etc. If Climate Change means these rivers will pack more punch due the atmosphere retaining more moisture, some engineered solutions that can hopefully not get the tribes spun up about fish can be devised.
Kitsap seems to have spared from most of the impacts of this event. Considering how many times they've been walloped in the past, particularly by snow storms and wind events, I have no doubt it was a welcome relief for them to not have the worst weather for a change.
DeleteGood to know Cliff.
ReplyDeleteProfessor Mass, the snow levels have seemed highly variable, but even at their highest a statistically significant portion of this moisture should have fallen as snow on the highest peaks, and certainly on 4 of our five volcanoes. Are you familiar with accurate data you can share to tell us what that represents?
ReplyDeleteYesterday, (Friday) coming home from work in Kent around 3:45PM or so, heading westward on the Kent/Des Moines Rd, the Green River was well over its banks and I could easily see it to my right side (north side of the road), between the road and the apartments beyond, normally, there is a path, brushland and the river, not so much, it was almost all under water, with some lapping at the very edge of Kent/Des Moines Rd. This did not include the development down by SR 181/68th Ave S. But the area west of there up to Meeker St. In spots, the river was still moving/swirling, but otherwise, still for most of the area to the north of the road. I could not see how it was to the south where the river went around 3 sides of a development near 68th Ave S.
ReplyDeleteIt was cloudy, but with some breaks in the clouds and the sun was low in the sky and as I drove south to Tacoma on I-5, the sky had tinges of magenta/orange in spots on the lower sides of the clouds, otherwise, they were a very dark gray/gunmetal in color.
Very unusual to have the Green River flooding in that part of Kent.
DeletePerhaps you can discuss how the use of ensembles of forecasts increases reliability. From my perspective, changing the initial conditions for the model generates a result that is equally likely as the initial simulation. Thus, I look at the rainfall predictions and I see that 3-7 inches of rainfall is forecast, but I have no idea of the uncertainty bounds.
ReplyDeleteAsk the farmers served by the Roza Irrigation District.
ReplyDelete