BillB Posted March 23, 2011 Share Posted March 23, 2011 I think I get the general concept of "dry air". I am thinking low humidity. I am also thinking we get "dry air" with "high pressure" systems. Now, if I am right about those two, why is it that during snow events that the meteorologists keep commenting on the storm overcoming the "dry air". What is it doing to the storm? Does it change what I expect to see on the ground? The main thing it is doing to the storm is getting in the way. The storm is transporting water. That water comes in the form of water vapor (gasseous form of water) and water droplets/snow crystals (forming clouds and/or precipitation). The air carrying this water is warmer and less dense than the cold dry air, and so it rides up over the top of the cold dry air. So when the rain/snow falls, it does so into the dry air underneath. This causes the rain/snow to evaporate. By this method, the storm has now added water vapor to the "dry air" and the evaporation cools the air; cooling the air temp and raising the dew point makes the air less "dry" and trends it toward saturation. This process continues as long as there is water available. As the dry air moistens, the rain/snow falls progressively closer to the surface and does its work at progressively lower altitudes. Eventually, it reaches the surface; at this point the fanatics on American Weather start cheering. This is how the storm "overcomes the dry air". Link to comment Share on other sites More sharing options...
HoarfrostHubb Posted March 23, 2011 Share Posted March 23, 2011 The main thing it is doing to the storm is getting in the way. The storm is transporting water. That water comes in the form of water vapor (gasseous form of water) and water droplets/snow crystals (forming clouds and/or precipitation). The air carrying this water is warmer and less dense than the cold dry air, and so it rides up over the top of the cold dry air. So when the rain/snow falls, it does so into the dry air underneath. This causes the rain/snow to evaporate. By this method, the storm has now added water vapor to the "dry air" and the evaporation cools the air; cooling the air temp and raising the dew point makes the air less "dry" and trends it toward saturation. This process continues as long as there is water available. As the dry air moistens, the rain/snow falls progressively closer to the surface and does its work at progressively lower altitudes. Eventually, it reaches the surface; at this point the fanatics on American Weather start cheering. This is how the storm "overcomes the dry air". For more reading, find EasternUSWX circa Feb 2010 for SNE posts... Lots of this Link to comment Share on other sites More sharing options...
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