Thursday, June 11, 2015

Casting a shadow - from Bartlett, TN to Alabama!

In the middle of mowing on a sweltering evening in north Bartlett last night, I was keeping a close eye just to the south as clouds began to gather. Having put a 10% chance of evening rain in the forecast a couple of hours earlier, I knew a shower was possible but really didn't expect much. Then this happened...

It was the only storm for over 125 miles (I guess a 10% rain chance was about right!).

Since it didn't budge, despite seemingly showing a slow northward drift initially, rainfall rates were impressive, owing to the high moisture content of the atmosphere with dewpoints near 70.

Though it lasted only about an hour, the cool part of this storm was not what happened under it, but what people saw from a distance, since it was isolated in nature.

First, looking south from Tipton County as it developed, courtesy of Mark Rapp:

And then from DeSoto County, looking north at a fully-developed storm, courtesy of "The Weather Mayor," Sam Rikard:

And up close, showing the rain shaft from the storm, courtesy of a different Sam Rikard (not a weather mayor):

And finally, from Winchester Road in southeast Shelby County, mad props to the king of iPhone photography, Joey Sulipeck, on this stunner:

Then the pictures started coming in not of the storm itself, but what the combination of an isolated, TALL storm and the setting sun produced! A stunning sky shadow that was visible on the east side of the storm (as the sun set behind it in the west).  First this one from Elizabeth Bouchoc taken at Briarcrest Christian School:

And this one from Collierville, taken by Kim Barron:

Then, perhaps one of the coolest atmospheric phenomena I've seen in some time, the same shadow showed up in CENTRAL ALABAMA! Followers of long-time Birmingham meteorologist James Spann sent pics like this:

He put a few pictures, including the one above, in a blog and included the graphic below. Though a bit difficult to make out due to low contrast, it shows the path the shadow would cast at sunset based on the angle of the sun, overlaid on a satellite image showing the storm cloud over Bartlett.

I put the coordinates in a solar calculator to verify the sun angle James came up with and, sure enough, because of the low sun angle (shown in yellow on the map below), the isolated nature of the storm, and it's height, a shadow was cast about 200 miles "downstream!"

Erik Proseus
MWN Meteorologist

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