Interesting weather satellite image from this evening. Most people are familiar with infrared satellite imagery which colors clouds different colors based on their temperature, even at night when human eyes can't see them. Well, This is infrared water vapor satellite imagery.
What does that mean?
Water Vapor imagery doesn't "see" clouds, it only depicts the amount of water vapor in the middle and upper troposphere and lower stratosphere. It doesn't show any clouds! Granted, we can infer that if there is a lot of water vapor somewhere, there probably are clouds there as well. But clouds are liquid water or ice crystals, not vapor (which is water in it's gaseous state). So what?
What is pointed out in the picture is the Jet Stream. Water vapor imagery is great at outlining the Jet Stream because the Jet Stream causes very dry stratospheric air to mix into the middle and upper troposphere...that's why you see dry air on water vapor imagery at these levels where my arrow point. Generally the more distinct the dry air is, the stronger the Jet Stream. The stronger the Jet Stream, the stronger the storm is that it is pushing along (over the upper Ohio River Valley in this picture).
Now, don't get confused...all dry air on this image is not the Jet Stream...other things can cause dry air to show up...but that's a semester-long course in advanced thermodynamics.
I'm sure y'all have heard of the "Polar Vortex"...a fancy name that someone created during the winter of 2013-2014 for the Jet Stream that becomes very strong and dips well into the southern states. It all starts with Water Vapor Satellite.