Near-Cell Environments of Tropical Cyclone Tornadoes

Accurately distinguishing and warning convective cells in the outer rainbands of landfalling tropical cyclones (TC) that will produce tornadoes (TCTORs) presents considerable challenges for forecasters. To enhance warning efforts, this study compares the near-cell environments between tornadic cells (including both warning hits and misses) and warned nontornadic cells (false alarms) in landfalling tropical cyclones in the contiguous United States from 2013 to 2020. For each cell, RAP analysis gridpoint proximity soundings were obtained to represent the near-cell environment and compared between tornadic and nontornadic cells. Warning skill with respect to various factors such as time of day, position relative to the TC center, distance from the nearest radar, and distance from the coast and year is also analyzed. Finally, this study characterizes the spatiotemporal distribution of sounding-derived convective parameters for TCTORs. Findings from this study indicate slight differences in the near cell environments between tornadic and nontornadic cells. Kinematic parameters, specifically the 0–6 km shear and effective storm-relative helicity, are more effective in distinguishing between tornadic and nontornadic near-cell environments than thermodynamic parameters. This distinction becomes most pronounced when comparing near-cell environments conducive to F/EF1+ tornadoes with nontornadic environments. Warning skill has improved with time over the analyzed period but tends to decrease farther from the TC center and the nearest NEXRAD WSR-88D. TC environments exhibit spatiotemporal variability across all environmental parameters. Convective instability is most prominent in the southeastern quadrant and increases with distance from the TC center. In contrast, shear and storm-relative-helicity is largest near the TC center and within the northeastern quadrant. The potential for near-storm environment parameters to discriminate between tornadic and nontornadic cells also varies spatiotemporally.