Diurnal Variability of Tropical Cyclone Tornadoes during Extratropical Transition

Tornadoes spawned from tropical cyclones (TCs) pose a significant threat to lives and property. Past climatological analyses have found TC tornadoes follow a diurnal cycle, peaking in the afternoon. Most of these prior analyses did not account for how tornado characteristics may change due to extratropical transition (ET), a process that nearly half of all TCs in the Atlantic Ocean undergo. ET is the process whereby a TC changes from a warm-core symmetric cyclone to either a cold-core or warm-core frontal cyclone. The kinematic and thermodynamic structure of the TC can be significantly altered by ET, thus influencing the convective-scale environment and suggesting the timing of tornadoes may also be affected. Hence, the present study investigates how ET impacts the diurnal variability of tornadoes and which factors are driving these changes. Here, we divide ET into three phases using the cyclone phase space: tropical (i.e., pre-transition), transition, and extratropical (i.e., post-transition). Preliminary results suggest that as ET progresses, tornado timing becomes later in the day with a greater portion of tornadoes occurring around sunset.