Tuesday, 5 October 2004: 8:45 AM
The present study examines the mechanisms that produce damaging, near-surface winds within bow-shaped convective systems. Recent idealized numerical simulations suggest that, in addition to descending rear inflow at the bow-echo apex, low-level mesovortices within bow echoes can induce damaging straight-line surface winds. In light of these findings, we have analyzed the detailed aerial and ground surveys of wind damage conducted immediately following six bow echo events observed during the BAMEX field phase. These damage locations were overlaid directly onto radar images to: (i) elucidate where damaging surface winds occurred within the bow echoes; and then (ii) explain the existence of these winds in the context of the theorized mechanisms.
We have identified the existence of mesovortices in three of six BAMEX bow echo events. In these three events, mesovortices were associated with the most intense wind damage. Limited diagnosis of single-Doppler radar data suggests that a stronger, deeper mesovortex is more likely to induce severe winds. More generally, we have found that the most intense RIJ/apex winds occurred within isolated, smaller-scale bow echoes, rather than within the extensive, larger-scale bow echoes.
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