The generation of this post came from a headline on my Comcast website (where I go to check my e-mail): "Rare picture of split mushroom cloud found" Here's the pic:
Apparently the "split" cloud over Hiroshima had already been seen in 1945; photographed by observers aboard one of the aircraft accompanying Enola Gay (tagged, by the way, with a terrific name for an implement of mass destruction: Necessary Evil).
Here's that snapshot - note that the upper "cap" cloud has pretty much separated from the "stem":
I mean, was this some sort of truly odd, unusual atomic phenomenon?
Did the split in the Hiroshima cloud indicate that some really peculiar atmospheric condition, or some bizarre anomaly in the detonation, had resulted in this strange cloud formation that was never seen again during the many atmospheric nuclear tests conducted during the Forties, Fifties, and Sixties?
The photo above is from the "Charlie" shot in the "Buster-Jangle" test series conducted in October and November of 1951. Note the double separations, the upper between the "cap" and "stem" as well as a lower split in the stem.
That led me to further research into the whole "mushroom cloud" business. Seems that these things are not just a nuclear signature. Any sufficiently large explosion will create them. The fireball of the explosion creates the "cap" as it rises, and the low pressure beneath the cap causes entrainment of the surrounding air and the moisture in the rising air condenses.
Not surprisingly, all this rising and condensing is dependent on the ambient air temperatures and pressures, so that if the rising cloud encounters a warmer air layer at altitude there will be no cloud formation, or the water droplets will evaporate again...
So it turns out that the photo itself was the big deal, if big deal it was, not the "split cloud".
And even that was not really all that such of a muchness; the photo had been published years earlier. It was the actual photo print that had been lost for some time and recently rediscovered.
So. No frightful new nuclear revelations, just a tiny bit of historical documentation come back to light.
Well, okay then. Let's dance!