The Use of Airborne Doppler Radar Radial Velocity Super Observations for Tropical Cyclone Prediction

Data assimilation using a Weather Research and Forecasting model (WRF)-based ensemble Kalman filter (EnKF) of P-3 tail-mounted Doppler radial velocities from the inner core of tropical cyclones has been shown to successfully represent the dynamic and thermodynamic structure of the tropical cyclone inner core vortex (Weng and Zhang 2012; Aksoy et al. 2012). WRF forecasts initialized from the EnKF analysis exhibited improved track forecasts at lead times beyond 12 h for Hurricane Katrina (2005) and improved intensity forecasts at lead times of 24 to 120 h for 61 tropical cyclones from 2008 to 2010 compared with the National Hurricane Centers operational dynamical models (Weng and Zhang 2012; Zhang et al. 2011).

NASA's Hurricane and Severe Storm Sentinel (HS3) field campaign to study mechanisms leading to tropical cyclone formation and intensity changes is employing a dual-frequency (Ka- and Ku-band), dual beam conically scanning Doppler radar - the High-altitude Imaging Wind and Rain Airborne Profiler (HIWRAP) (Heymsfield et al. 2008) - mounted on a Northrop Grumman Teledyne RG-4A Global Hawk UAS. A preliminary study using an observation system simulation experiment (OSSE) has demonstrated the potential use of this remote observation system for tropical cyclone prediction (Sippel et al. 2013, in press).

Using the Pennsylvania State University (PSU) WRF-EnKF assimilation system and an adapted version for the Navy's Coupled Ocean-Atmosphere Mesoscale Prediction System for tropical cyclones (COAMPS-TC), the forecasts of Hurricane Karl (2010) are examined for ensemble simulations assimilating P-3 and Global Hawk HIWRAP airborne Doppler radar velocity super observations (SOs). The SO generation methodologies for both P-3 and HIWRAP Doppler radial velocities are discussed.