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Howard B. Bluestein

Abstract

Photographs are presented that illustrate the various forms in which “flanking lines” exist in nature. Flanking lines may appear not only as the commonly observed sloping line of cumulus congestus, but also as erect towers with a vertical face, and as a line of altocumulus castellanus above and parallel to a band of stratocumulus lenticularis. It is suggested that the slope of the tops of the flanking-line towers with respect to the ground is related to a quantity that is similar in form to the bulk Richardson number, and that the orientation of the flanking line is a function of the mean wind in the lowest 6 km and storm motion. These hypotheses need to be verified when high-resolution, rapid-scan, visible and infrared satellite imagery become available on a daily basis.

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Howard B. Bluestein

Abstract

Photographic evidence is presented of funnel clouds pendant from the bases of convective clouds whose updrafts appear to be rooted well above the boundary layer. These funnel clouds occur in environments supportive of severe convective storms, under dissipating cumulus humilis, cumulus congestus, and low-precipitation cumulonimbus, and on the rear side of supercell and multicell convective storms. Since these funnel clouds do not become tornadoes, spotters should learn to distinguish them from the potentially tornadic funnel clouds that occur under convective clouds that are rooted in the boundary layer.

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Howard B. Bluestein

Abstract

This is a case study of a mesoscale area of convection which began at night over western Kansas on 2 September 1982 and lasted until the afternoon of 3 September. Evidence from analyses of surface, upper-air, radar, and satellite observations suggests that the thunderstorms probably formed in response to the lifting of an elevated layer of conditional instability. The lifting can be attributed qualitatively to quasi-geostrophic ascending motion resulting from a shallow layer of warm advection near 60 kPa. Two possible sources of moisture were midlevel moisture which had been advected around an upstream ridge and a localized area of turbulent transport of water vapor from below. The convective event could not have been forecast with synoptic-scale, mandatory-level analyses alone; it was difficult to explain even with detailed analyses at other levels.

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Howard B. Bluestein

Abstract

Photographs of several severe storm related phenomena are described. A double wall cloud having a double vortex structure evolved from a single wall cloud, and subsequently turned back into a single wall cloud and produced a tornado. In addition, a double funnel cloud was observed under a curved, high-based cloud extending eastward and southeastward from the wall cloud region.

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Howard B. Bluestein

Abstract

The characteristics and environment of low-precipitation severe thunderstorms in the Southern Plains have been summarized by Bluestein and Parks in 1983. Photographic documentation is given here of several storms not previously shown.

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Howard B. Bluestein

Abstract

Photographs are presented of wall clouds having holes or small regions of raised cloud base new the center. These eyelike features may be due to descending air (Lemon and Doswell) near the middle of the mesocyclone circulation or to the ingestion of relatively dry air into the updraft (Fankhauser et al.,).

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Howard B. Bluestein

Abstract

Tornadoes are often reported as tropical cyclones make landfall. In this note I present photographic evidence of a possible funnel cloud in the eye of Hurricane Norbert in the Eastern Pacific, far from landfall.

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Howard B. Bluestein

Abstract

The rare occurrence of a tornado in the Sierra-Nevada region of California is documented. The synoptic-scale wind and pressure field and the thermodynamic structure of the environment are discussed.

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Howard B. Bluestein

Abstract

No abstract available.

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Howard B. Bluestein

Abstract

Photographic and mobile-radar documentation of the dissipation of a supercell and a severe convective storm that had not yet developed into a mature supercell are discussed. It is hypothesized, based on these cases and on others, that when a low-precipitation or classic supercell and/or a developing supercell moves into an environment of cooler surface temperatures and a strong capping inversion, it eventually dissipates through a process of “downscale transition,” in which vertical shear tilts the updraft more in the downshear direction as the CAPE decreases, and the updraft becomes narrower as the storm dissipates. During the downscale transition, it is possible that a cold pool or lack thereof may play a role, but the documentation in the cases detailed herein is not adequate to address this issue.

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