This has been the year for violent thunderstorms and deadly swarms oftornadoes. At last count nine major cities have been impacted directly orindirectly by an EF-3 or stronger tornado.After a brief lull early in May, severe thunderstorm activity has picked upagain. This recent surge in activity can be attributed to a large upper-airtrough that has developed over the Central states.
Meteorologists use that phraseology quite a bit without explaining it fully. Atrough is a term describing the jet stream when it dips southward, forming aU-shaped pattern. Within the trough, the upper portions of the atmosphere areeither cool or cold, depending on its intensity.
Since the air is free to flow in different directions at different altitudes, acold pocket in the upper atmosphere is able to move across a region occupied bywarm, humid air. This makes the atmosphere become very unstable, and there ismuch upward and downward commotion. In turn, thunderstorms form, whichsometimes become quite severe.
In addition, big upper atmospheric troughs can wring out a lot of rain. We feelthis will happen from the Gulf states to the Appalachians during the nextcouple of days, and right to the East Coast after that.
Story by AccuWeather.com Senior Meteorologist John Kocet.
