Combining Real-Time TDWR Data with NEXRAD Data for Nowcasting and Numerical Weather Prediction

In North Texas there are regions of the Dallas-Fort Worth (D/FW) metropolitan area that are covered at relatively close range by up to three Federal operational Doppler radars. There are two Federal Aviation Administration (FAA) Terminal Doppler Weather Radars (TDWRs) serving the Dallas-Fort Worth Airport and Love Field in Dallas as well as a National Weather Service (NWS) operated WSR-88D (NEXRAD) radar in Fort Worth, and other NEXRAD radars that cover parts of the region from a distance. The combination of these radars provides multiple-Doppler radar coverage of many parts of the metro area. While it is rare to have multiple TDWRs in a metro area, there are many other areas in the country that have dual-Doppler coverage when TDWR data are combined with NEXRAD data. As part of the Engineering Research Center for Collaborative Adaptive Sensing of the Atmosphere (CASA), the Center for Analysis and Prediction of Storms (CAPS) had developed and a 1-km resolution real-time nowcasting and numerical weather prediction system (NWP) and ran the system in a domain covering central and southwest Oklahoma. In anticipation of the CASA radars being moved to North Texas and the establishment of an urban testbed in the D/FW area, the domain for this data assimilation and NWP system was relocated to the D/FW area in the spring of 2012. Access to the Level-II TDWR data from the two D/FW radars was arranged through NOAA, and CAPS adapted code to read and process these data for the NWP system. The impact of the addition of the TDWR data to the data assimilation is demonstrated with data from the 3 April 2012 tornado outbreak in the D/FW area. Compared to analyses using NEXRAD alone, the TDWR data increases the strength of the analyzed updraft helicity in the supercells and improves the wind analysis in regions surrounding the cells (Fig. 1). Comparisons of NWP results with and without the TDWR data will also be shown.