Have you watched our weather reports before and wondered what exactly is happening in the atmosphere when we call it a “disturbance” or even an “upper level disturbance”? Well, think of it as a dip in the jet stream.
These dips are areas of lower heights. They are literally low spots in the jet stream flow. So as the air flow into the dip, it sinks down into the low area. However, as the air passes farther east (weather moves generally west to east in our part of the globe), it begins to rise. What does that matter? Well, it’s rising air that creates clouds, showers, and thunderstorms. Sinking air erodes the clouds and often brings in drier air.
So when a dip in the jet stream (a disturbance) is approaching from the west, we have unsettled or stormy weather up until the dip is right over the top of us, then the sinking air comes in overhead and we clear out.
Take this weekend for example. The forecast is for scattered storms possible later Saturday with better chances on Sunday. Why? because the disturbance will be approaching us on Saturday and a few showers are possible, but it should be very close and still just west of us on Sunday with better rain chances. However, by Monday the disturbance is to the east and our weather begins to clear out once again.
– Storm Track Chief Meteorologist Matt Miller