Monday, 6 August 2007
Halls C & D (Cairns Convention Center)
The National Weather Radar Testbed (NWRT) in Norman, Oklahoma is a multi-agency facility and partnership that began testing a US Navy Phased Array Radar (PAR) in 2003 for severe weather applications. The rapid scanning capability of the PAR (wavelength 9.38 cm, 500 kW peak power, 100 m range resolution, 1.57 micro-sec pulse width) provides a volume update rate of 58 seconds compared to a minimum of 300 seconds for the conventional WSR-88D radar. Also, scanning strategies with the PAR can be easily adapted for higher rate update of a sector volume as opposed to the fixed continuously rotating antenna of the WSR-88D. This rapid volume-scanning capability allows for characterization of the meso-gamma-scale (2-20 km, 3-30 min) evolution of storm structure (reflectivity) and related kinematics (radial and perhaps cross beam velocities). This information can be interpreted by nowcasting tools such as TITAN (Thunderstorm Identification Tracking Analysis and Nowcasting) to quantify storm characteristics (including trends in storm intensity and tracks), determine storm motion and produce very rapidly updating nowcasts (0-45 min forecasts) of storm location and evolution. In this study we explore the utility combining the rapid scanning capability of the PAR and TITAN nowcasting software to characterize the 3D evolution of an evolving squall line that propagated through the NWRT on 17 June 2005. The entire squall line, individual cells and hail shafts (> 60 dBZ) are tracked separately in three-dimensions across the PAR field of view using TITAN. The skill of TITAN nowcasts was very good, but decreased with at the smaller storm scales. Individual cells often developed, merged and split confusing the tracking software at the finer scales. However, because of the rapid scanning capability, accurate nowcasts can be generated for newly developing storms in a fraction of the time (~3-4 min vs 15-20 min) required when using slower scanning radars such as those used in the WSR-88D network.
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