Modifying Windsonds to Improve In-Storm Measurements

Abstract. Obtaining reliable thermodynamic and kinematic profiles from within severe convective storms presents a challenge for radiosondes due to the extreme conditions to which the instrumentation is exposed. The Windsond S1 has emerged as a popular tool for severe storm research; however, exposure to heavy precipitation has been recently documented to cause relative humidity (RH) sensor malfunctions, limiting the reliability of in-storm measurements. We introduce modifications to the Windsond S1 design that limit water ingress and thereby mitigate these issues. The modifications include a redesigned radiation shield that blocks falling raindrops while maintaining adequate ventilation, a stabilizing support arm, and a tether seal. Controlled experiments using irrigation-generated precipitation at approximately 300 mm hr^-1 demonstrated that unmodified sondes experienced RH sensor failures, suppressed RH variability, and power failures due to water ingress, while modified sondes remained functional throughout the exposure to the extreme rain rate. Validation profiles comparing modified and unmodified sondes launched under varied atmospheric conditions, including nocturnal flights, showed temperature differences of typically less than 1 °C and RH differences less than 10 %, with no systematic biases introduced by the modifications. These design improvements were applied to an extensive number of Windsonds S1 during the 2025 ICECHIP field campaign for in-storm deployments. Tested modifications to the Windsond S1 require minimal expertise to implement. Further, design files have been made publicly available to support the broader severe storms research community.