TOPEKA (KSNT) – If you have a good eye for weather, and picking up small details, you may have noticed that our thunderstorms have been generally moving from east to west lately. To a faithful watcher of the skies that may seem a bit backwards.
Here’s a satellite / radar loop from some thunderstorm activity this past Friday. Notice the storms firing up over the Kansas City area and then moving west into our neck of the woods.
Usually, our jet stream (the fast moving highway of winds – 30,000 feet up in the atmosphere) carries our showers and storms from west to east. In the mid latitudes we sometimes refer to this phenomena as “prevailing winds” or “westerlies”.
So, why the sudden change in direction then?
To answer that question we have to take a look at what is going on up in our atmosphere. Things may get a bit technical from here – but bear with us!
This image above is called a ‘skew-T’ and is graphed by plotting a few different variables from a weather balloon launch. We won’t get into too many details about skew-T’s here, but just know that it shows weather data from different levels of the atmosphere.
The surface (from where the balloon was launched) is at the bottom, and the top of the graph represents where the weather balloon popped (near the edge of space).
On the right side of the graph we have circled what are called ‘wind barbs’ and they show two important details:
- The lower and mid-level winds are blowing from the east to the west.
- The winds are also quite weak for being so high up in the atmosphere (20 to 25 mph).
So not only is the wind direction moving from east to west, but it’s also moving quite slow. That’s one of the reasons we’ve been seeing flash flooding too with recent thunderstorms.
Now, we head to the surface for our last clue as to why storms have been moving in this odd manner.
- This surface map shows a large high pressure system over the North-Central plains and a low pressure system over the Pacific Northwest.
- Surface winds around a low pressure system flow in a counter clockwise direction
- Surface winds around a high pressure system flow in a clockwise direction.
Thus, due to our proximity to the high pressure system, our surface winds have generally been blowing from east to west as we hang out on the southern periphery of the circulation. Any thunderstorms that fire up here will tend to follow that same circulation.
When you put all of the above factors together it becomes a bit more clear as to why our showers and storms have been acting a bit different lately!