An analysis of low-level moisture flux convergence prior to the 3 May 1999 Oklahoma City tornadoes

The availability of high time resolution boundary-layer wind, temperature and moisture around the tornadic thunderstorms which developed on 3 May 1999 offers an unprecedented opportunity to study the evolution of the lower-level moisture flux convergence fields needed to support the development and continued growth of these storms. In addition to data available from the inner-core of the Wind Profiler network, data from five co-located Atmospheric Emitted Radiance Interferometer (AERI) instruments provided detailed temperature and moisture data for the lowest three kilometers of atmosphere at ten minute resolution in clear sky and to cloudbase.

Although the AERI data alone can be used to monitor the evolution of the convective available potential energy (CAPE) and convective inhibition (CIN) at each of the instrument locations, the combination of the moisture and temperature information with wind profiler observations facilitates detailed studies of the dynamical processes involved in modifying the pre-convective environment and focusing the energy needed to subsequent convection. The results shown will focus on:

- Determining the dynamical processes responsible for both increasing the depth of the low-level moisture source and enhancing the convective instability,

- Evaluating the relative roles of divergence and advective processes in supporting the low-level moisture convergence structure, and

- Assessing the implications that these finding have on the relative roles that improvements in depicting wind field dynamics (e.g., numerical models) and observations of moisture gradients (e.g., observing systems) will have in future severe storm prediction systems.