Before we talk about how the jet stream is impacting our very wet forecast, we have to understand what the jet stream is.
The jet stream (located about 25,000 feet above the Earth's surface) is the boundary between the cold Polar air to the north, and the warm tropical air to the south. The extreme difference in the temperatures (and resulting differences in densities) between these two air masses causes this current of fast-moving winds.
This current is thousands of miles long, but only a few hundred miles wide.
This thin band of winds is responsible for pushing around many of our weather systems around the world. The jet stream is the reason most storm systems move from west to east. In order for us to see cool, dry air move in we need the jet to dip far enough south to move in that cooler, Polar air mass.
Instead, what has happened is the jet stream has remained over Canada and the extreme Northern U.S., bottling up all the cool, dry air and keeping the Southeast hot, humid and stormy.
We can't only blame the jet stream. In the low levels we're also seeing an area of high pressure to our east that continues to pump in high moisture levels from the Gulf. That's thanks to the clockwise winds that circle a high. If one's to our east, we see high humidity.
Additionally, the mid-levels have refused to cooperate. We've seen many upper level disturbances move through that aid in destabilizing the atmosphere. Combine that with the low level moisture and the placement of the jet, and you have all the ingredients of this yucky stagnant pattern we will continue to see through next week.
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