Most of the time, atmospheric rivers--plumes of lower-atmospheric moisture from off the Pacific Ocean--are relatively wide and thus produce large amounts of precipitation over a broad region.
But on Friday, something relatively unusual occurred: a very narrow "mini" atmospheric river was locked over our region for hours, producing a narrow band of intense precipitation over western Washington and into the Cascades.
You can really see it in the regional weather radar image for Friday morning (below). Yellows indicate the heaviest precipitation.
The southwest-northeast plume of heavier rain was very evident. Totally dry over the San Juans and the southern Cascades.
Consider the precipitation totals on Friday below (only values more than a third of an inch are shown).
You can clearly see the precipitation band; where the moisture plume was forced to rise by the central Cascades, 3-5 inches fell.
Local rivers have surged, some to near flood stage. The black dots below show the rivers that are now experiencing MUCH above normal flow.
The UW WRF model accurately predicted this moisture plume the day before. Below is the prediction (for Friday morning) of water vapor flux (the amount of water vapor brought in by the wind). Orange shows the highest amounts. Not bad.
Reservoir levels are moving up rapidly as a result.
Friday was kinda fun for just riding around on my bike and watching the morning unfold. The way it developed, looking at the radar Friday morning, I assumed it was a convergence zone.
ReplyDeleteIn any case, I saw more flooded steets on my bike between downtown snd Georgetown than I think I have ever seen in Seattle. Venice for a day!😅
I stayed inside on Friday, opened up the blinds, and watched it rain from the (relative) comfort of a stationary bike. On Saturday, I couldn't bring myself to ride that thing on a third consecutive day, so I did a ride out in intermittent light rain. I won't claim to have invented backward time travel, but 105 minutes outside in the rain still feels like less saddle time than 90 minutes on a stationary bike.
DeleteIt has certainly been a very wet month-to-date in Western Whatcom County. With nearly 5” of rain, it’s been the 6th wettest 1st half of November on record in Bellingham.
ReplyDeleteNo need to apologize for it being November! November is supposed to be wet and rainy in these parts, and this year, that is exactly what is happening.
ReplyDeleteI'm impressed that the coast picked up far less rain from this atmospheric river compared to the mountains. It goes to show to difference elevation sometimes makes with these atmospheric rivers.
Even neater that it actually included some brief breaks - I had to be out in a wheelchair using transit between QA Hill and the U District, and managed to stay dry both directions.
ReplyDeleteI, for one, welcome our beneficent soggy overlords!
Yawn...as usual, Everett and vicinity was in a mostly "rain-shadowed" area...moderate rain at best.
ReplyDelete'So right to mention the DROUGHT monitor. Another year, another "wet drought." Can anybody get that squared away? Whether it's "rain year" or "YTD" ...there's no way that makes sense. I've repeatedly knocked on doors (I participate in a WRIA watershed planning unit) and some say "it's pure SNOTEL data," others have side-stepped that to say "it's the river-flow prediction people" and it becomes just a circle "pass" (that term polite enough?). Our water table(s) [aquifers, aquitards, all sorts of geological-hydrogeological terms] are saturated, "despite the summer."
ReplyDeleteCan you do a post on the Yakima Valley situation? What are the chances of some recovery this year?
ReplyDeleteHere's a plot of the Yakima total storage (includes all reservoirs) for the water year: https://www.usbr.gov/pn/hydromet/daily_grapha.html?list=yaksys%20af
DeleteIt has seen some rapid filling over the last few weeks but is still below normal, but so far doing much better than last year at this point. It is still early in the water year so a long way to go, but if we continue to have a normalish water season and get a reasonable snowpack in the watershed you would think the situation will be better than 2024-2025.
In the past three weeks, that reservoir system has already jumped from 7 percent up to 18 percent capacity. And we are just getting started.
ReplyDeleteI think that the drought monitor people start counting after New Years Day. By that measure we're still behind. But they do show alarmist tendencies. If you look just at this "water year" (i.e., the rainy season so far) then we're on target.
ReplyDeleteFrom a human perspective, Thanksgiving has always been associated with extremely heavy rain from what I recall some of the most graphic flooding happened around Covid locally , since that time it's been relatively lessened Maybe we are in some sort of a lil but prior to that Covid flood we've never had such insane flooding so I don't think there's any pattern to any of this alleged drought.
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