Dropsonde-derived Vertical Velocities from the 2015 Tropical Cyclone Intensity (TCI) Experiment

In this study, vertical velocity was calculated from 442 eXpendable Digital Dropsondes (XDDs) that were launched into tropical cyclones (TCs) Marty (27–28 September), Joaquin (02–05 October), and Patricia (20–23 October) during the Office of Naval Research 2015 Tropical Cyclone Intensity experiment. The vertical velocities were evaluated based upon their strength, locations in the TCs, and the environments that they occurred. The strength thresholds used were moderate (90% percentile), strong (95% percentile), and extreme (99% percentile) for updrafts and downdrafts. The strongest updrafts and downdrafts occurred in the cores of the TCs and aloft above 10 km. The azimuthal locations of the strongest convection were heavily modulated by the magnitude and direction of the 850–200-hPa shear. Updrafts above the moderate threshold tended to occur in locations of low bulk Richardson number, low horizontal wind speed, cool temperatures in the outflow layer, dry air in the outflow layer, strong pressure gradient forcing, and warm and moist low-levels. Non-thermally driven extreme updrafts tended to occur in areas of supergradient flow, turbulence, or sharp gradients in the horizontal and vertical winds.