Yesterday on the way in which house from the UW, I ended on the native grocery store to purchase some meals and a few chilly beer.
However I may hardly see into the refrigerated instances: they had been utterly lined with a thick veneer of condensation.
I imply a LOT of water (see beneath).
Why was there a lot water vapor within the air?
Usually, the preliminary phases of main warmth waves are related to downslope circulation on the Cascades that’s comparatively dry.
Then I received a couple of emails from people in northwest Washington complaining in regards to the humidity.
OK, I had to determine what was occurring.
One of the best measure of absolutely the quantity of water vapor within the air….the “stickiness” and discomfort.. is the dew level temperature.
That is the temperature to which it’s important to cool air all the way down to for saturation (100% relative humidity). For dry air it’s important to cool it down loads to get it to saturation.
So dry air has low dew level temperatures. And moist air has excessive dew level temperatures. Right here in western Washington, the dew level temperatures in summer season are typically within the decrease 50s. Even decrease dew factors are typical in dry japanese Washington.
To determine the state of affairs, I plotted up the dew factors at this time across the area and was shocked (see beneath)
For instance, the dew factors round 11 AM this morning had been 70F in Bellingham and round Vancouver. And nicely into the 60s round Puget Sound.
These are very excessive dew factors for our area. The one time they had been larger in latest reminiscence was through the massive warmth wave final June. Very heat temperatures can evaporate a whole lot of water and trigger excessive dew factors, however our temperatures at this time, though heat, weren’t even near final summer season.
The best dew factors had been over the comparatively cool northwest WA/Vancouver space.
Attention-grabbing, high-resolution numerical climate prediction fashions, just like the UW-WRF mannequin, predicted the excessive dew factors over NW Washington (see beneath for 11 AM Tuesday, gentle inexperienced colours point out larger dewpoints.)
So what was the origin of this humidity storm?
First, this warmth wave didn’t have sturdy circulation from the east like many warmth wave durations. Such circulation could be drying, with an origin east of the Cascades and decrease humidity from the heat related to sinking air on the western slopes of that mountain vary.
However then I appeared on the atmospheric moisture coming off the Pacific: a plume of very excessive moisture values was circling across the excessive stress offshore. That is proven by the moisture and pressures/heights close to 10,000 ft on Sunday as proven beneath (crimson and gray indicated excessive moisture values). You possibly can see the moisture transferring across the excessive on the north facet.
This moisture rotated across the excessive and moved into Northwest Washington (see the ten,000 ft moisture Tuesday morning, beneath)
The air that reached the floor close to Bellinghan and Seattle originate northwest of these cities and descended out of the moisture patch all the way down to the floor, warming because it descended. We will see that from the 3-D path of air reaching Seattle this morning (see beneath). The highest panel reveals the spatial path and the underside one reveals the elevation of the air (later to the left). The air was descending quickly on July 24-25.
In abstract, a plume of moisture from deep over the Pacific rotated across the excessive after which descended to the floor. And through the remaining few hours, it was over the moist western facet of our area.
Properly, after exploring this example, I made a decision that I deserved some ice cream to assist me cool off a bit.
I open my freezer….and I used to be surprised by what I noticed….one thing that’s related to moist air being chilled to beneath freezing. Life has its frustrations….
