Typically on the rare occasions that we get thunderstorms in the Northwest, they are so weak that those in the Midwest would scoff to even call them thunder'storms'. But the storms this week have been a little more ornery than usual.
So ornery, that the forecasters at the National Severe Storms Laboratory in Norman, Oklahoma -- the ones in charge of issuing severe thunderstorm and tornado watches -- actually put out a discussion on the weather along the Oregon and Washington coast today. (Normally they treat our area like Atlantis -- like it doesn't exist. But that's understandable because the weather here is so rarely worthy of their attention.)
- I'll be doing real-time storm forecasting and posting updates all day on Twitter. Follow me @ScottSKOMO
Their conclusion was that while some of the storms could reach minimum severe thresholds, it's not enough to warrant a Severe Thunderstorm Watch today. But by our standards, some of the storms are looking quite active. Why? Because we have a few added ingredients in place to add some extra oompf to our usually tame (lame?) storms.
Our thunderstorms right now are being caused by a cold and unstable atmosphere, further aided by low pressure offshore that continues to spin moisture our way. Explaining unstable air without using really crazy charts is difficult, but in a nutshell, unstable air means that atmospheric conditions are such that it is easier for parcels of warm air to rise higher into the sky, which is more conducive to cloud and storm development.
Unstable air can occur when you have cold air moving in the upper layers -- that is our most common unstable air occurrence. And right now, we have some very cold air from the Gulf of Alaska moving into our upper layers, thus creating a greater temperature drop as your gain altitude than normal. That's aiding in vertical lift and adding strength to the storms.
But in addition, we also have some wind shear in play today -- that's what you get when you have air flowing in different directions at various levels in the atmosphere. This can cause some rotation as the winds collide and spin.
You can see this wind shear visually by just looking at the sky today and watch the clouds move in different layers. Or, check out these videos from the UW time lapse cameras:
Note how the low clouds are moving one way, and the higher clouds are moving another. Picture putting a thunderstorm in there and that shear can cause some funnel clouds. Now, that said, these are typically "cold core" funnel clouds that are weak and mostly harmless, not the major tornadoes that occur in the Midwest. In fact, we just went through a round of those on Feb. 7
But then again, some clouds might look like funnel clouds, but aren't. The key is to look for rotation. Check out this quick tutorial I made during those Feb. 7 things:
This quick video does show rotation:
This shows clouds that might look like funnels, but aren't:
So keep an eye to the skies today. If you capture video or photos of cool clouds, or lightning, or funnels, let us know via e-mail and post it to our YouNews site and we might use it on air and online.
For More Information From Previous Weather Blog Entries: