Crazy Blue Line, What is it?? | Weather
First and foremost we have strong storms across N Georgia tonight. As of 1am nothing is severe, but don't be surprised if another warning pops up tonight..... That last storm in Forsyth and Hall was on its way down when the NWS issued the warning, I doubt there will be any reports of damage from it. We can expect storms to continue to propagate towards the south tonight, but the main source of energy is now gone.... Which is what this blog is all about.
Gust Front / Outflow Boundary
It is all the same thing. Basically the mechanism for feeding a line of thunderstorms is a moisture pump into the storms as they fire up along the advancing front. This front is formed by rain cooled air that rushes ahead of the line of storms. The line you see is not actually rain, it is very cool air being compressed into a small roll of clouds called an outflow boundary. The reason the radar picks it up is because of the tremendous changes in density in the atmosphere where the "roll" is. When the line of storms' inflow (the air getting sucked into the storms) is in perfect balance with the rain cooled air rushing out we can get a long lasting squall line or derecho (you can google both of those terms or wait for my blog tomorrow). Sometimes that advancing front gets moving faster than the storm can keep up with and the warm air that is feeding the storms gets choked off. That is what is happening tonight. From the images below you can see that the blue line is advancing much faster than the storms can keep up with. That is how you can tell that the storms are going to wind down.
We will continue to monitor the storms this evening and let you know through the blog what is going on. For more updates follow me on facebook and twitter: