Poster Session P11.6 Scales of motion in tornadoes, what radars cannot see, what scale circulation is a tornado

Thursday, 7 October 2004
Joshua Wurman, Center for Severe Weather Research, Boulder, CO; and C. Alexander

Handout (3.0 MB)

Tornadoes have been observed to manifest intense small-scale wind maxima, low reflectivity eyes, and surrounding high reflectivity regions. However, extremely high resolution observations in some tornadoes have revealed that there are multiple scales present and that concentric windfield and reflectivity structures may be aliased to larger scales and result in misleading imagery by radars that are not extremely close to the phenomena. Several 'ground truth' Z and V fields are compared to simulated DOW, SMART, 88D, CASA and ELDORA data at 10 km range. V and Z fields from all these radars suffer from severe aliasing, failing to capture various true tornado features, while imaging 'eyes' and V couplets that are mostly due to larger scale circulations, not the actual tornado.

DOW observations of several large tornadoes and large surrounding circulations are compared in order to examine when a circulation is a tornado, compared to a mesocyclone or multiple vortex. Determining whether a multi-scale circulation is a mesocyclone with an embedded tornado, or a tornado with embedded multiple vortices is difficult.

In situ radar observations in an extremely large, 2-4 km scale, circulation, with an intermittent embedded tornado are presented. Winds corresponding to 3-sec 75 ms-1 gusts were observed at 10 m AGL very near the DOW radar.

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