Meteorology of A Dusty Day in the Valley

Days like this don’t come around too often in this part of the country; that hazy, dusty look to the sky is caused by: dust.

A dust storm kicked up in Nebraska, Kansas, and Oklahoma on Thursday put enough fine particulate matter in the lower atmosphere to cause a moving “cloud” of dust that blew into Alabama and Tennessee this morning. Here’s the latest MODIS visible satellite image showing the progress of the dust across the Tennessee Valley this afternoon:

The brownish band from Central Mississippi through North Alabama & East Tennessee is the dust cloud that originated in the Plains Thursday.

Here’s a short animation from CIMMS showing the dust plume’s movement: CIMMS Satellite Imagery.

How do we know where it came from? There’s a really neat tool called the NOAA Hysplit Model that can work backward showing where air “parcels” originate. Over the past 24 hours, the air that was over southwestern Nebraska has pushed all the way through North Alabama into North Georgia and East Tennessee. That explains how we can have such a gusty southwest wind yet still get an air flow from Nebraska…a state far to our northwest. Notice also in the lower portion of the image below that the air not only flows straight across the ground; it also can ascend and descend throughout several thousand feet in the atmosphere. That spreads out the dust and gives us that hazy look:

The wind is blowing around a strong area of low pressure near the Great Lakes; this is the same storm system that brought tornadoes to Mississippi and rainy, stormy weather to the Valley on Wednesday night.

Tonight’s sunset should be a pretty one! Be sure to get your cameras out, and send your photos to photo@whnt.com! Sunset time this evening is 6:06 PM!

Speaking of photos, here are some the dust pictures we have received so far today. We will add more as they come in!

The dust will pass on through the Valley tonight and Saturday will be a clearer day! For more on the forecast through the weekend, be sure to check out the detailed discussion over at WHNT.com/Weather!

-Jason
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