Analysis of Tornadic and Nontornadic Convective Cell Environments during Hurricane Harvey

Tropical cyclones contain many hazards including storm surge, flooding, severe winds, and tornadoes. The later of these can pose a forecast and warning challenge as tornadoes associated with tropical cyclones (TCTORs) can be less predictable and more difficult to detect than tornadoes in other environments. Consequently, there is a need for a robust environmental and radar climatology of the convective cells in the rainbands of land falling tropical cyclones. Building on earlier results focused on the Houston-Galveston NWS WFO (HGX) during Hurricane Harvey, this study compares radar and near cell environments of tornadic and non-tornadic (but tornado warned) convective cells for all of Harvey’s duration.

To do this, all tornado warnings that may be associated with Harvey and tornado reports, using the TCTOR database were cataloged. Vertical gridpoint profiles from Rapid Refresh (RAP) model analyses were collected to determine the near-cell environments for each false alarm or tornadic convective cell. Near-cell environment attributes and general statistics such as time of day and distance and bearing from Harvey’s center, as well as composite soundings were calculated and compared between tornadic and nontornadic cells.

Preliminary results indicate that despite significant overlap in most environmental parameters between the groups of tornadic, non-tornadic, and tornadoes with and without a tornado debris signature (TDS), a select number of parameters such as Storm Relative Helicity, the magnitude of the 0-6km shear, the 0-3km Lapse Rate and Mixed Layer CAPE, the Supercell Composite Parameter (SCP), and the Significant Tornado Parameter (STP), had a noticable difference between one or more groups. The composite sounding thermodynamic profiles look similar between the four groups with the primary differences appearing in the hodographs. Finally, the distance, bearing, and time of day preliminary analysis reveals that tornadoes and tornado warnings in Harvey appeared to have a preferred quadrant, and range of times of day and distances from Harvey’s center. These results, and further analysis of radar attributes for each cell will be presented.