Features Along The Leading Edge: shelf clouds and vaulted cloud structures

This rather innocuous appearing squall line probably is more typical in appearance than some of the spectacular squall lines we have been viewing. Note the subtle shelf cloud ahead of the dark precipitation area. This was a non-severe squall line in eastern Oklahoma in the fall, looking west from about 5 miles.

[Image: Non-Severe Squall Line-Eastern Oklahoma (59K)]
Photograph by: Doswell

Underneath the shelf cloud and looking north, note the change in appearance from the ragged, outflow-torn clouds to the smoother elements ahead of the line. The outflow winds had commenced at this time, and hail and heavy rain were to arrive in minutes.

[Image: Squall Line Leading Edge (57K)]
Photograph by: Moller

This strong gust front (shown below) was accompanied by 40 and 50 MPH winds and a shelf cloud with a highly-sloped concave shape to the underside.

[Image: Vaulted cloud structure at the rear of the squall line leading edge (61K)]
Photograph by: Moller

Near the light area on the southwest horizon, a downburst was resulting in damage at this time, as reported by Amateur Radio Spotters southwest of Fort Worth, Texas. The squall line was moving eastward (right to left).

on satellite images

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Credits and Acknowledgments for WW2010.
Department of Atmospheric Sciences (DAS) at
the University of Illinois at Urbana-Champaign.

retreating lines