Warning Improvements
Storm-Targeted Radar Wind Retrieval System
Doppler velocity field with overlapped retrieved wind field around selected TVS at 22:16UTC on 8 May 2003. Warm colors denote velocities away from radar. Cool colors denote velocities toward to radar. The radar is on the cross-point of two solid white lines outside of this image. (larger image)
Scientists recognize through theory and observations that low-level vertical shear, horizontal convergence and/or rotation of horizontal winds in a pre-storm environment can play critical roles in severe storm initiation and intensification (Davies-Jones 1984; Lilly 1986; Xu et al. 1996). The strength and direction of low-level wind shear and non-uniform environmental conditions determine where new storm cells will develop. An existing “normal” storm can be enhanced by the presence of a boundary in the atmosphere, such as a cold front, thunderstorm outflow, or land/sea breeze. It can develop into a tornadic storm as the available environmental vorticity is tilted and stretched. During a severe storm or hurricane, strong low-level winds can be hazardous and damaging in many ways. Their strong winds carry airborne debris that can be life threatening. In the case of hurricanes, wind-driven coastal waves and storm surges can be catastrophic (as recently witnessed from Hurricane Katrina). In these circumstances (either prior to or during a severe storm), timely and accurately analyses of low-level wind conditions at high resolutions becomes critical for severe weather warnings and monitoring. Such analysis tools are still lacking. Most weather forecast offices have access to single-Doppler radial winds (one component of the horizontal wind) but not the full horizontal vector winds at the same high resolution. To solve this problem and provide a desired comprehensive analysis tool, researchers at NSSL and OU/CIMMS (Zhang et al. 2005) are developing a storm-targeted radar wind retrieval (STWR) system. The STWR system contains two relatively independent components: Warning Decision Support System-Integrated Information (WDSS II) (Hondl 2002) and two-dimensional simple adjoint radar wind retrieval (2dSA) (Xu et al. 2001). WDSS II provides the capabilities to execute various existing algorithms, such as mesocyclone detection, TVS (Tornadic Vortex Signature) detection (Stumpf et al. 2002), and to display the results in real time on its interactive interface. The 2dSA can retrieve very-high-resolution storm winds (up to 250 m) from radar scans. An example is shown above.
References
Davies-Jones, R., 1984: Streamwise vorticity: the origin of updraft rotation in supercell storms. J. Atmos. Sci., 41 , 2991-3006.
Hondl, K.D , 2002: Current and Planned Activities for the Warning Decision Support System-Integrated Information (WDSS-II). Preprints, 21 st Conf. on Severe Local Storms, San Antonio, TX , Amer. Meteor. Soc., pp 146-148.
Lilly, D. K., 1986: The structure, energetics and propagation of rotating convective storms. Part I: Energy exchange with the mean flow. J. Atmos. Sci., 43, 113-125.
Stumpf, G. J. , T. M. Smith, and A. E. Gerard, 2002: The multiple-radar severe storm analysis program (MR-SSAP) for WDSS-II. Preprints, 21st Conf. on Severe Local Storms, San Antonio, TX, 138-141.
Xu, Q., H. Gu, and C. J. Qiu, 2001: Simple adjoint retrievals of wet-microburst winds and gust-front winds from single-Doppler radar data. J. Appl. Meteorology, 40, 1485-1499.
Xu, Q., M. Xue, and K. K. Droegemeier, 1996: Numerical simulations of density currents in sheared environments within a vertically-confined channel. J. Atmos. Sci., 5, 770-786.
Zhang, P., S. Liu, Q. Xu, and L. Song, 2005: Storm targeted radar wind retrieval system. 32nd Conference on Radar Meteorology, 24-29 October 2005, Albuquerque, New Mexico, Amer. Meteor. Soc., CD-ROM, P8R1, Conference CD.
