During the previous few days have you ever observed the dryness of the air? See a spark while you touched a doorknob or that your pores and skin appeared unusually dry? Or a dry throat and the urge to drink extra water? Garden soils appear desiccated?
You usually are not alone. Many on the western facet of Washington State famous the phenomenon, which I’ll time period a Dry Storm. And it’s about to get revved up once more!
To get some perspective, here’s a plot of the relative humidity at Seattle Tacoma Airport over the previous six months. Two days in the past, the relative humidity dropped beneath 15%, the bottom since October 29th.
At Olympia, Monday introduced the bottom relative humidity for your complete six months.
As lots of you understand, relative humidity describes the diploma to which the air is saturated: the quantity of water vapor within the air divided by the utmost quantity of water vapor air can maintain on the present air temperature. Since heat air can “maintain” extra water vapor than chilly air, there are two elements that affect relative humidity: the quantity of moisture within the air and temperature. Thus, with the identical quantity of water vapor in a pattern of air, the relative humidity is decrease throughout the hotter time of the day.
So what concerning the quantity of water vapor within the air, say at Olympia. A very good measure of water vapor content material is the dew level temperature: the temperature to which air has be cooled to saturate it (100% RH). If air is filled with water vapor, you do not have to chill it as much–thus, larger dew level. The plot beneath exhibits a plot of dew level at Olympia over the previous six months. It was fairly low, however not as little as October 29th. The very low RH on Monday was the mixture of low water vapor content material and a comparatively heat day.
So why was the relative humidity so low on Monday and why is it going to occur AGAIN on Thursday? Good query.
It has to do with the climate sample we now have been in, with a big higher stage ridge and inland excessive stress pushing dry air from the Northwest inside westward into western Washington.
Let me present you a collection of relative humidity forecast maps for our area…and I warn you, you may placed on some lip balm earlier than you view it.
This morning we now have had a little bit of a moist reprieve. The forecast floor relative humidity map for five AM exhibits larger values (blue colours) as moist air flooded western Washington. There are a number of low clouds this AM. No marvel I slept higher final evening.
But tonight, cooler air and excessive stress will transfer into Montana and Idaho, creating offshore (easterly) move over our area. The forecast map for five AM Thursday (beneath) exhibits this, with blue colours indicating cooler temperatures. Look intently (or click on on picture to broaden) and you’ll view the floor winds being offshore-directed over Washington State. Note the air warming because it descended the western slopes of the Cascades–that is because of compression warming as air goes from low stress aloft to larger stress on the floor.
The relative humidity forecast forecast for five PM Thursday (beneath) is, nicely, withering west of the Rockies, with some values in western Oregon and Washington getting beneath 15%. We can name it Dry Storm2.
The floor air west of the Cascade crest won’t solely be dry however heat, with highs within the higher 60s over Puget Sound and 70s within the Willamette Valley (see temperature forecast beneath for five PM Thursday). Reds and pinks are the warmest. And sure…no rain. This persistent sample has resulted in primarily no precipitation over us for the previous two weeks and none is anticipate throughout the subsequent 7 days.