Cirrus fibratus grades to a street of cirrostratus, with a fading old contrail mixed in for good measure. This all wafted over an iconic and legendary meteorological spot: the Mount Washington Observatory. An unusually calm, splendid day belies the thoroughly wretched and dangerous conditions that often blast this place in the cool season. With no barrier to low-level jets blowing from any … [Read more...]
Ominous, Nearby Wall Cloud
[Part 3 of 3] Less than a mile to the NW, the wall cloud had a very low base for an LP storm and was furiously rotating. The scalloped "humps" on the right (NE) side of the wall cloud raced rapidly up and around its side, spiraling in a frantic dervish of helicity. The four chasers on the scene, all hardened storm veterans (me, Bobby Prentice, Gene Moore and Jeff Passner) were thinking aloud … [Read more...]
More Rotan LP
[Part 2 of 3] Cyclonically curved bands are visible in the ambient cloud base, especially in front of the wall cloud (upper center). These bands spiraled from left to right; while scud formed near the tip of the rear tail cloud and moved right to left. This is textbook, mesocyclonic wall cloud structure. A downburst at right had dissipated, leaving only a thin, translucent remnant core … [Read more...]
Rotan Wall Cloud
[Part 1 of 3] Sample the evolution of a close, rotating wall cloud in a briefly classic supercell evolving back toward LP (low-precipitation) structure. Tiered inflow tail structures give this wall cloud a double-decker appearance. A difluent rain foot from a small forward-flank microburst is visible at lower right, north of the mesocyclone. The chunk of scud in front of the wall cloud (upper … [Read more...]
Line-Embedded Mesocyclone
Shortly before this image, a portion of the line just to the left of this shot, containing the rear-flank downdraft to this circulation, hit the Memphis, TX mesonet site with 114-mph gust. That was the strongest nontornadic wind of an extensive severe-weather event that kept rolling east over most of Oklahoma in the next few hours. This short-lived, moderately rotating, embedded circulation … [Read more...]
Cryptic Current, See?
No convection had appeared in the sky an hour before, yet a fast-developing, fast-moving squall line rushed forth with blasts of lightning, embedded mesocirculations, and even severe hail. The atmosphere can evolve speedily! At the very spot where nearly six years before, I had shot a classically structured, discrete supercell, on this evening I faced a furiously chaotic and growing band of … [Read more...]
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