The visible satellite image this morning was stunning, reminiscent of an image from mid-winter (below). The star shows the location of Seattle.
You can see the swirl of clouds around a deep low-pressure center west of British Columbia, a strong front offshore, and unstable air with convective clouds south and southeast of the low.
Impressive.
It is times like this that we should be glad that we have a coastal Doppler radar (thank you, Senator Cantwell), which shows the approaching frontal rain band offshore (see below).
This rain will come in later today, bringing another period of moderate precipitation.
Below is the latest high-resolution UW WRF model forecast of accumulated precipitation through 5 AM Saturday morning.
Very, very wet in the mountains, with large areas getting more than 3 inches.
Rivers are going to surge rapidly, as illustrated by the predicted discharge on the Snoqualmie River near Carnation (below). If you go to Snoqualmie Falls on Sunday, you won't be disappointed.
Another interesting aspect of this event is the high humidity today. Dew points are reaching the mid-60s, making it feel sticky ....reminiscent of the East Coast.
Note: the dew point is the temperature to which air needs to be cooled to reach 100% relative humidity. The higher the dew point, the more moisture the air has.
There are some amateur YouTube sites and some media claiming that this is a highly unusual, record rainstorm.
This is not true.
Having a strong event like this in mid-August has occurred numerous times before. Below is a list of the record one-day totals for mid-August (Aug 4-21) at Seattle.
Yesterday's total of .22 inches was 44th on the list. Today, SeaTac may get a half inch, which is certainly not without precedent.
The PWAT values are indeed record breaking for ANY time of the year. The Weather Prediction Center Day 1 excessive rainfall outlook points this out as well. This is what I was reffering to in my video today.
ReplyDeleteMichael.... I am not talking about PWAT (Precipitable Water) but rainfall. PWAT is very high, but the dynamics of this system are relatively weak; thus the precipitation will not be extreme. We can get high values of PWAT during the summer without much rainfall.....the key to getting heavy rainfall is to have strong uplift from an incoming system, which is MUCH stronger during the winter, when PWAT is generally lower because the atmosphere is cooler..cliff
DeleteCliff, how long until the dewpoints in the 60s abate? I turned on my a/c today just to get a break from it.
ReplyDeleteThe major forecast services called for substantially more precipitation than I’ve observed to this point during this event so the amateurs perhaps aren’t entirely to blame for overshooting the mark. If you actually compare precipitation as measured by a high-quality rain gauge with forecast amounts you’ll find that precipitation forecasts are generally less reliable than temperature forecasts for any given location.
ReplyDeleteWhy did this happen? It seems like it is something that happens now and again - is it weather from Alaska?
ReplyDeleteBig rainshadow over Seattle, as always.
ReplyDeleteHow fascinating! Here in north Whatcom County (north Cascades) we've had any number of recent summers with significant precip in August - most recently just last August 2024 (7 am Aug 24, 2024 I reported 1.33" for the 24-hr period, to CoCoRaHS). My point is: heavy summer rain has NOT been a rare phenomenon. Over my 50+ years observing here, it's been generally interpreted as "an early fall." And, so this may be yet again. It certainly "feels like an early fall" to me in most respects here in Glacier.
ReplyDeleteCliff, is the coastal Doppler the unit at Pacific Beach or is it south of there on the coast? Perhaps the Pacific Beach unit is Navy?
ReplyDeleteJust north of Hoquiam
Delete47.116878, -124.106725
DeleteIt seems we have a "switch" like this at the end of August or in September where the possibility of hot weather and prolonged dry weather is over for the year. Lots of good 70 degree weather for sure but not likely anything in the upper 80s. I wonder if this is that "switch".
ReplyDeleteEvery year is different. 1991 saw some decent rain in late August, but the weather rebounded to produce a dry streak that lasted into mid-October. September wasn't abnormally warm, but the first half of October was. Eventually, the above average temps broke, and the last week of October saw daytime highs below 50 and some frosty and freezing nights.
DeleteIt could be. But it can still get quite warm for shorter periods, even in late September. Don't rule out 8 and 90 degree temperatures completley until October.
DeleteLooks like the North Pacific water is way above average (blob 2.0 ?) particularly off our coast. That driving the humidity?
ReplyDeleteIt was an exceptionally gloomy August day in the Bellingham area, as well. I measured a maximum solar irradiance at my location of just 134 W/m^2 and a total of only 2.5MJ/m^2 of solar energy.
ReplyDeleteRain this time of year is normal. We always take a hike on the High Divide in the Olympics in mid-August, and we have been rained on numerous times up there. We've been through a few doozies up there. Love it!
ReplyDeleteAs a Christian I will share a unique opinion about Cantwell “suffer not a woman to be in authority” (the Famous Jewish apostle Paul)
ReplyDeleteThis event was definitely record-breaking in the Vancouver area. Vancouver Harbour (downtown) received 68.6 mm (2.7") of rain yesterday, making it the wettest August day on record there, with records going back to 1898. It was also the second wettest August day on record at Vancouver Airport, with 43.2 mm (1.7") or rain yesterday.
ReplyDeleteDefinitely wet here in T-Town yesterday, though not a gullywasher by any means, but a good, solid, steady rain much of the day with periods of no rain, but a good portion of the day was rather, "drippy". A nice change from the usually omni present sun and warm to hot but dry temps. Definitely a sign that fall is around the corner.
ReplyDeleteNoting that the next 10 days via the Weather Channel site, getting nice mid week, but temps staying mostly lower 80's or so, and full on sun for several days but yeah, kinda agree, the really warm days of much over 85 are past.
In fact, next Friday and Saturday, 83/84 is all that is written before temps drop back to the mid 70's as we get into the next week and partly cloudy skies.
That said, this wet weather we've had yesterday (Fri) is not uncommon and many years, we've had a day or 2 of this mid August or so, then the warm/sunny pattern returns for roughly another month, usually coinciding with the Puyallup Fair, which means by mid September, we see some of the first signs of the rainy season while the fair is on. I remember one year, I forget which, 1978/79? coming back from Grants Pass Or, we ran into cloudy/rainy weather on the way home, especially as we went into the mountain ranges that leads past Roseberg but I think it was the same much of the way home to Tacoma.
! inch on Orcas as of 6 am this morning
ReplyDeleteWhile this event doesn’t stack up compared to the very rainy system(s) late last August, KBLI did record a new daily record of 1” of rainfall on 8/15 - the 10th wettest August day in its POR.
ReplyDelete