That time has come once more. The time when our lakes sometimes seem to boil with tendrils of vapor reaching skyward.
Surreal, however stunning. Northwest steam fog season is right here..
Saturday Morning From Magnuson Park, Seattle
Close up, steam fog could be delicate, like this picture taken round 7:50 AM on Monday:
But at different occasions it’s merely beautiful, particularly when illuminated by the solar:
Steam fog happens when chilly air passes over heat water– often water that’s at the least 10-15F hotter than the air proper above it. 20F variations often produce an excellent present.
Why steam fog?
To get fog you want two issues: bountiful water vapor after which cooling the water vapor laden air to 100% relative humidity (referred to as saturation).
The commonest fog round our area is radiation fog, and in that case the ambiance begins with a specific amount of water vapor after which the land cools (by emitting infrared radiation), which in flip cools the air close to the floor to saturation.
Steam fog is a bit totally different (see determine). You begin with a comparatively heat water floor, which in flip warms and moistens a shallow stage close to the water. That alone just isn’t sufficient to present us a lot fog in any respect. Then we transfer in some chilly, however comparatively dry air above it. If there may be some wind, turbulence and mixing between the chilly/dry air and the nice and cozy/moist air happens, and the MIXTURE is each sufficiently moist and funky… it’s saturated and fog varieties.
The air above provides the cooling and the water provides the moisture.
Neither can produce a saturated layer by itself, however collectively they’ll. Sort of like epoxy cement, by which solely when the contents of two tubes are combined can the actual motion happen.
So what was the temperature state of affairs this week?
The air temperatures dropped into the thirties round Lake Washington on Monday morning and right this moment, as illustrated by the temperatures this morning at eight AM (see under)
And what about water temperatures?
King County has a buoy proper in the course of Lake Washington, between Magnusson Park and Kirkland and measured a water temperature of about 56F, whereas the air temperature on the buoy was 39F (4C) on the similar time (see under). A large enough distinction for steam fog!
Tomorrow (Sunday) morning could also be even cooler, so that you would possibly think about in search of some steam fog by Lake Washington and Lake Sammamish in case you rise up early. But carry a heat drink.
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