Collision course with an anvil

A towering cumulonimbus cloud denotes atmospheric instability in western Nebraska.

You can see it coming for a hundred miles or so out there in Nebraska, freeway bearing northeast and quickly-mushrooming anvil cloud bearing southeast, aiming to meet in another hour right where you have a motel reservation. It’s hard to imagine anything could sneak up on anyone on the plains, where you can see forever because the corn doesn’t obstruct a single sight line. No surprises. Just enormous storm clouds that seem to stalk you, perhaps menacingly, but that’s anthropomorphizing, as anyone can tell you that storms just barrel in without stalking.

Bright, they are. Cumulonimbus (Cb) cloud tops are full of ice crystals reflecting the brilliant sunlight, tricking you into thinking it is a Safe Thing when its Latin derivation suggests otherwise: cumulus “heap,” nimbus “storm/rain.” One look at these monstrous upwellings of air and water vapor and you sense that its unsettled nature will likely bring precipitation.

Dangly clouds are not my favorite.

Just to the north, the lowest layers seemed to be dragging heavily from the cloud bottom. Seeing no rotation, I didn’t get the sense of a tornado; it was nonetheless disconcerting. The cloud was dangling. Dangling clouds, to midwesterners, are often unsafe. These photos taken at 70 mph with my iPhone don’t do justice to the mysterious nature of  the pannus variety of cumulonimbus, but at least now Wiki has given me a name for it:

Fractus clouds (scuds) are small, ragged cloud fragments that are usually found under an ambient cloud base. They form or have broken off from a larger cloud, and are generally sheared by strong winds , giving them a jagged, shredded appearance. Fractus have irregular patterns, appearing much like torn pieces of cotton candy. They change constantly, often forming and dissipating rapidly. They do not have clearly defined bases.

Sunset illuminates a cloud-shred.

Thirty minutes later, this towering giant was so electrically charged that I counted 28 flashes of strobe-like lightning in 60 seconds. It felt alive, some sci-fi monster rumbling in its innards, ions and updrafts and unstable air converging on North Platte just outside my motel room. I stood alone at the  west-facing window and trembled involuntarily, several hundred megawatts of electrical power staring me in the face; until it weakened, there would be no sleep.

Clouds on the mesa

One hour before sunset in late July. Gray’s Pasture, Island in the Sky, Canyonlands NP, Utah.

MONSOON. The word conjures up images of driving sheets of heavy rain pummeling a coastal village, causing widespread flooding and general misery. Here in southern Utah, however, monsoons take a different approach. July, August, September are our months when thunderclouds can kick up, lightning arrives to make mesa-top living more interesting (and dangerous), and the clouds drape themselves in our skies like no other season of the year. We rangers love monsoon season.