Textbook Backshear NW of Norman

August 26, 2006 by
Filed under: Summary 

About two hours ago (as I type this), from Norman, I photographed a young multicell/supercell hybrid in Kingfisher County, about 60 miles away.

2105Z, Looking NW

Despite the distance, the cloud base was somewhat visible. Because of the hot inflow air and large dew point depressions, the LCL was high. It helped also that the boundary layer wasn’t too hazy. The best part was the development of a classical backshear on the west side, and a large “knuckle” (upside-down, moist convective cloud element) immediately adjacent to where the new updraft plume was roaring up into the anvil.

2108Z, Looking NW

Although I’ve seen this kind of structure numerous times in much more robust and sustained supercells, seldom have I photographed it. There’s no good reason for that, so why not start now, with a marginal storm but (nonetheless) an excellent visual specimen?

Ambient deep-layer shear was marginal today with only 20-25 kt of 500 mb flow and variable SE-SSW surface winds, but this storm had help down low. It formed at the intersection of an outflow boundary and a prefrontal surface trough shown on the graphic for this mesoscale discussion (available for the rest of 2006), and was a later version of the same “VIGOROUS YOUNG CB” mentioned in the text. [I just waited ’til right after getting off duty to run up to the roof and snap a few shots.]

We won’t be seeing cumulonimbi from the old NSSL building for very long. It’s possible these will be the last cloud photos anyone ever takes from there, in along and storied history of such dating back to a tornado over what is now far NW Norman in the early 70s. In less than a month the SPC operational forecast unit will move to the new National Weather Center. To get to the roof will require a lot more time and effort than just running two stories up one bank of stairs, but the view will be even more remarkable.


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