A Radar-Derived Synopsis of the Rapid Tornadogenesis in the 01 April 2023 Hazel Green, Alabama EF-3 Tornado

On 31 March 2023, confidence increased in the probability of a severe weather outbreak across much of the Mississippi River Valley and two separate high risk regions were denoted by the Storm Prediction Center (SPC) by 1630Z. An intense Quasi-Linear Convective System (QLCS) was expected to move across the southeastern United States from Arkansas and Southern Missouri during the late afternoon to evening hours into portions of North Alabama. Given the 30% hatched tornado probability from SPC and the linear nature of the system, the Propagation, Evolution, and Rotation in Linear Storms (PERiLS) project opted to deploy systems across Northwest Alabama and Southern Tennessee to gather data on tornadogenesis in linear storms. During the early morning hours of 01 April, a violent tornado formed near the town of Hazel Green, Alabama within the QLCS as it trekked eastward. This tornado would prove to be amongst the strongest of tornadoes produced from this system with maximum estimated winds of 145 miles per hour (mph) (64.8 ms-1) and causing one fatality. A sounding launched from the Severe Weather Institute - Radar and Lightning Laboratories (SWIRLL) located on the campus of the University of Alabama in Huntsville at 0757Z showed a surface-based Convective Available Potential Energy (CAPE) value of 629 Joules per kilogram (Jkg-1) with a 0-6 kilometer wind shear value of 73 knots. This high-shear, low-CAPE profile is common in the Southeast during the cool season and is a driving factor in the purpose of the PERiLS field campaign. Numerous civilian weather stations near the site of tornadogenesis recorded wind gusts near 50 mph immediately before a sharp pressure increase of 2 millibars occurred around 0810Z. The location of tornadogenesis provides an excellent opportunity for dual-Doppler analyses (DDAs) to be performed using the National Weather Service Weather Surveillance Radar - 1988 Doppler (WSR-88D) in Hytop, Alabama (KHTX) and the Advanced Radar for Meteorological and Operational Research (ARMOR) located at the Huntsville International Airport in Huntsville, Alabama. KHTX (S-band) is located 70 kilometers at 63° from ARMOR (C-band) which provides a clear dual-Doppler coverage zone over Hazel Green and the entire path of the tornado. The resulting DDAs will provide insight into the orientation of the wind field near the time of tornadogenesis and document the rapid intensification of the tornado during its lifetime. Further analysis on this tornado will feature the incorporation of PERiLS data to diagnose the QLCS in its evolution over North Alabama with an emphasis on the structure of the Nocturnal Boundary Layer (NBL).