WeatherWeather Blog


Why Have Storms Moved East To West Recently?

Explaining the abnormal storm motions
Posted at 5:44 PM, Jun 07, 2023

In the United States, our weather pattern generally flows from west to east across the nation. Storm systems typically come ashore over the Pacific, move over the western US, emerge into the Great Plains, and drift off into the eastern US. This is around how 90% of our storm systems operate that affect Nebraska. However, as mentioned a few weeks ago with blocking, sometimes our weather pattern can grind to a halt.

That "Omega block" we saw a few weeks ago came back by late May, and has been responsible for the string of hot days with scattered afternoon storms. This pattern continues through the week, but looks to finally break down into this weekend.

Omega Block.PNG
The jet stream on May 24, notice how the jet stream resembles the greek letter Omega?

Through this week, keen observers of the radar and the sky might have observed something curious. Our storms, when they develop, move westward. 90% of the time in Nebraska and Iowa, storms move to the east, northeast, or southwest. (I.e. storms affect Millard before Council Bluffs; Lincoln before Omaha etc.). However, the storms this week have come from the east, in Omaha that meant CB saw the rain first before the Nebraska folks did. Why is this? Well, it has everything to do with the weather pattern we are in.

Storms tend to follow the herd of the wind pattern, and only occasionally steers away from the flow. Since the wind normally flows west-to-east across the country, this explains the storm motion to the east.

Recall in the blog about omega blocking that a central feature of it (literally) is a large dome of high pressure that pushes the jet stream well to the north over Canada. In this current iteration of the pattern, that high pressure system sits on the North Dakota/Canada border. One low pressure system sits in the northeast, the other near California.

Remember that areas of high pressure tend to flow clockwise, and areas of low pressure tend to flow counter-clockwise. Because that high pressure sits to our north, the flow around that high pressure over Omaha is from the east around it. Since storms tend to follow that flow, they are moving from east to west.