I was looking through the UW 12z extended WRF-GFS, and in one of the model frames, I saw an "unsettled" pattern. Meteorologists always talk about unsettled weather. But what does unsettled weather really mean?
"Unsettled" weather does NOT refer to nice weather. Most of you knew that, but I thought I would just make it clear. More surprising though is that "unsettled" weather generally doesn't refer to super stormy weather either. If we had a huge flooding event or a massive windstorm or even a gargantuan blizzard, people would not refer to it as "unsettled."
According to Dictionary.com, "unsettled" means "not settled." Thanks Dictionary.com. However, Dictionary.com goes on to explain that "unsettled" means "not fixed or stable." What comes to your mind when the weather is "not fixed or stable"?
It's the ol' proverbial Seattle "showers and sunbreaks!" Seattle generally sees these "showers and sunbreaks" after the passage of a cold front, and a lot of cold fronts pass through our area in the autumn, winter, and spring seasons. The weather can be especially "unsettled" in the spring, as the higher sun angle provides more thermal energy for stronger showers but also makes us warmer and sunnier when the clouds have parted. Have you ever heard people say things along the lines of "don't like the weather now? Wait 30 minutes." In most areas, this is not true. Most of the time, the weather in 30 minutes will be the same as it is at the time of this trite, overused saying. With Seattle though, that can actually be true following the passage of a cold front. And if you really want it to be true, go to the coast. I remember one day in April of 2008. I was on the coast, and it was exceptionally cold for that time of year. The highs around Western Washington were on either side of 45 degrees, which is very cold for that time of year. The reason for these low temperatures was that we had a large pool of cold, moist, unstable air originating from the Gulf of Alaska over our area. Coupled with a high sun angle, we truly saw some amazing weather that day.
I was razor clamming when it started graupeling. Mozilla Firefox gives me a red line under "graupel" so I'll go ahead and explain what it is. Many of you have seen it and not realized it. Graupel looks like "snow pellets" and is common within the convective showers we see in the winter and spring, especially when the atmosphere is very unstable. See the picture below.
Graupel on a roof!
But the story doesn't end there!!! After it had been graupeling for a while, my body had a large static charge, and I could clearly sense it. Every time I touched metal, I was shocked. I heard buzzing sounds around me. My hair stood up on end. I was in danger of being struck by lightning, so I rushed back inside. I'm glad I didn't get struck!
A few minutes later, the sun came out, the clouds abated, and my mom decided to take me and my brother for a nice Saturday drive.
But the atmosphere had not calmed down yet. After a nice sunbreak, clouds started rolling in again, and I saw, with my own eyes, the formation of a weak tornado. This tornado was nothing like the tornadoes in the Great Plains - it is called a "cold-core" tornado. "Cold-core" funnel clouds and tornadoes are the result of local areas of circulation in thundershowers, not rotating mesocyclones like the ones in truly severe thunderstorms. I wrote a post on this blog in the past explaining the differences between Midwest tornadoes and Pacific Northwest tornadoes, so if you are curious, you should check that post out. The tornado looked sort of like this one, taken over Lake Washington.
8/25/08 - 8:45 a.m. Picture taken from Bellevue by anonymous resident, and this picture is from Scott Sistek's weather blog "Partly to Mostly Bloggin'."
Even while we were watching this weak tornado, we were in a patch of blazing sunshine.
That was a memorable day because I saw so many different types of weather in such a short period of time. That, my friends, is what unsettled weather means.
In our area, "unsettled weather" (showers and sunbreaks) has a very characteristic satellite appearance. The following picture was taken right after the passage of a cold front. You can see the cumulus and cumulonimbus clouds that imply that there is an cool and unstable pool of air after the front. This picture was actually taken the same day that all these crazy weather events happened, and I think that the cloud near Grays Harbor had the tornado that I saw! Weather archives are cool.
02:30 pm PDT Sat 19 Apr 2008
And here is an example of what an "unsettled" pattern might look like on radar. The cold front precipitation ends right around the coast, and the "unsettled" showers and sunbreaks are offshore. One of them in particular looks like a real heavy shower, can you find it?
03:36 am PDT 3 October 2011
That is all I have time for today. Thank you for reading! The next time you hear that there will be "unsettled" weather, just think showers and sunbreaks, and in some cases, showers and sunbreaks on steroids!