Sunday, January 18, 2009

Ascent of Tiger Mountain and Warm Temps

Today was a very different day than those of earlier this week in a number of ways. First, the fog and low clouds were considerably reduced west of the Cascades, particularly in the afternoon (see the sat picture at 2 PM). Low clouds did remain east of the Cascades and extended into the pass.

The pressure difference across the Cascades increased to 14 mb...higher to the east. This large pressure gradient helped to drive strong easterly winds. Some of these winds reached the surface over the eastern lowlands...from North Bend to Samamish..and when they did, the cold air was scoured out the temps jumped to near 60F. But nearly regions which remained in the cool air, below the inversion, were 10F or more colder.
The Seattle profiler showed the strong easterlies (actually southeasterlies aloft) and the profound change in the inversion and temperature structure aloft (see figure from 7 PM Sat to 7 PM Sunday). Last evening we had inversions galore... the old inversion aloft and a new radiation inversion at the surface (produced by radiational cooling at the surface). During the afternoon, the surface warmed up and the warm air above mixed down and the inversion become greatly weakened. With dry warm air mixing down, visibilities (from the Puget Sound Clean Air Agency webcams) soared....take a look at the difference between the visibility today at 3 PM and two days ago...pretty dramatic. You can see some of those residual low clouds in today's image.
As many of you have done, I hiked up Tiger Mt. today...from 500ft in the parking lot to 2522 ft at the West Tiger 3 summit...referring to a high-accuracy thermometer and an aneroid altimeter on the way up. We started at 9:10 AM--36F. There was a large temperature changed in the first 500 ft (to around 46F at 1000 ft). This was the surface-based radiation inversion. Then between rougly 1200 and 1900 ft the temp climbed into the mid 50s (the second inversion) and we entered the realm of the strong easterlies. At the top, the temps reached around 60F (high was 61.4). Excellent visibility in all directions. There was some snow on the shaded slopes in the last few hundred ft. I was impressed how much the snow level had risen on the Cascades...looked like 3000-3500 ft on the western slopes.
Looking at the computer models tonight...stuck by the lack of precipitation for the next week....nothing there really.

16 comments:

Anonymous said...

Even now the temperature spreads are wacky. 48dF at Paine and 36dF at Boeing Field...first time I can remember PAE being 12 degrees warmer than BFI.

Driving around on I-405 this afternoon, our car's temp gauge changed more than the speedometer: 59 in Totem Lake and 53 at Factoria...a 1-mile stretch of Lakemont Blvd had a 5 degree temp spread!

Liembo said...

One thing I don't like about these temperature inversions is the increased freeway noise from nearby I-405. We're about half a mile from it and normally the sound isn't really an issue, but today it was particularly noticable. (Thank you, Scott Sistek for your explanation on why: http://www.komonews.com/weather/blog/34608154.html)

Anonymous said...

Experienced at least 60 degree temps today during a hike at Hurricane Ridge. Amazing stuff...felt like a nice day in May.

fjblau said...

Out here in Sammamish... went for a walk around 3PM... It started out a little brisk, but with every breeze you would get this gorgeous warm air blowing across the park!

andycottle said...

The UW 00z WRF-GFS is just now coming out and it shows light southerly winds tomorrow at 850mb with temps at around +12c. So with the 2m temp/wind profiler chart showing the inversion being less than 1000ft tomorrow and light SELY surface winds, perhaps the eastside Puget sound folks could see another day of upper 50`s to low 60`s.

Currently 36 with clear skies ata bout 1145pm here in Woodinville.

Jeff said...

Here on the north end of the Sammamish Plateau we had a high Sunday of 64.3F, breezy all day and east wind gusts at 17.1 mph. The sky was so clear and so blue!

Around 2-3pm we were on the Issaquah Highlands which was equally as warm with absolutly no wind at all. Protected from the backside I suppose.

This morning it is 44.6F here and breezy. I see the lowlands very nearby are in the low 30's and upper 20's.

I love the east wind. I lived in North Bend for years and always enjoyed those days we were so much warmer than anywhere else. The loggers didn't much appreciate it in the Summer because Weyerhauser would shut down the woods due to fire danger.

Anonymous said...

This morning in Sammamish, it's about 7 degrees cooler than it is in Seattle....our Wunderground instruments read 29.3 degF

andycottle said...

Another clear morning here in Woodinville with my temp reading 29 degrees and dew point of 25 here nearly 8am. Perhaps another mild day like yesterday? We`ll see. :o)

fjblau said...

28.4 over by the Beaver Lake ballfields!

www.seattlebuskers.com/wx

Ignore the 3 hour flatline yesterday... software glitch!

Anonymous said...

Liembo, Saturday evening I was walking home, just west of Aurora Ave (99), and was amazed at how loud I-5 was. It made me think that I must have been really drunk, but I only had my normal weekly dosing of 3.5 pints. I-5 is about 1 mile to the east, but it sounded like it was only 3 blocks away. I wonder if the Green Lake has any effect. Some days I can never hear I-5 in my neighborhood, and other days it sounds like it is next door.

Anonymous said...

Liembo, I was driving north on I-5 through Snohomish county at about 9am Sunday morning. Near Lynnwood's 44th Avenue exist, the mountains looked huge and close. About 4 minutes up the road, they looked small and distant. I enjoy that phenomenon(?) when driving west on 520 across Lake Washington. The change in appearance of the Olympics is fascinating.

SnowLover said...

I want Winter back. :(

Anonymous said...

With reference to your observation of surprisingly high snopack, the NASA Aqua images shows the same thing. It looks like late spring.

Anonymous said...

I agree SnowLover!!!!!

Anonymous said...

It has been amazing here east of North Bend. The winds were very strong yesterday--I wouldn't call it breezy, but the temps were about 60 in the Middle Fork Snoqualmie valley where we are...behind Mt. Si from North Bend. It's still windy today, but more on the breezy side and not quite as warm so far. It's a little unnerving watching 100' pine trees waving in the wind.....just as long as they fall thatta way, as opposed to thissa way!

Anonymous said...

Went for a hike from Alpental to Snow Lake on Sunday (low avalanche risk according to NWAC site). As pointed out here, pass was in a cloud and this remained so up to just below the ridge above the lake (about 4000 ft); then brilliant sun. Temps were quite cold (below freezing) but at the ridge there was a strong wind mixing things up so it wasn't warm. I did hit a few pockets of surprisingly warm air on the ridge, however. Interesting to watch how the cloud layer from eastern WA melted just as it was about to cross the mountain crest.