Thursday, 7 October 2004: 8:45 AM
The 8 May 2003 Oklahoma City supercell storm was observed by the Twin Lakes (Norman) WSR-88D (KTLX) during its entire lifecycle. Careful analyses of reflectivity and velocity data (at ranges varying from ~115 km to as close as ~10 km) reveal many details of the overall storm structure and evolution. After a pulsing multicell beginning, the right-moving storm acquired supercell characteristics (mesocyclone, bounded-weak-echo-region, and hook echo) approximately 30 minutes before the beginning of the tornadic phase (about 2200 UTC). The storm split three times with shorter-lived left- movers, none of which were as strong as the right-mover. As the right-moving storm began its tornadic phase (a short-lived F0, followed by a longer-lived F4), the previously strong mid-level mesocyclone extended to include a strong low-level mesocyclone and a strong tornado cyclone/tornadic vortex signature. Low-level rotational features were preceded by strong radial-component convergence in the lowest kilometer above ground. Mesocyclone and tornadic signatures weakened rapidly as the tornado dissipated. Later cyclic storm behavior is not discussed. The Oklahoma City storm structure and evolution is similar to a number of previous radar studies of supercells. Illustrative two-dimensional data plots and time-height diagrams of the storm are compared to high-resolution numerical model outputs of the same event (Part II and Part III).
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