Abstract
Previous studies have shown that vertically misaligned circulations are commonly found in weaker tropical cyclones (TCs) below hurricane strength, whereas TCs of hurricane intensity more typically exhibit vertically aligned vortices. Thus an important step in the TC intensification process is achieving a vertically aligned circulation. The present study is the first to perform a comprehensive, observational comparison of how the TC vortex and convective characteristics differ between Quickly Aligning and Persistently Tilted TCs. Airborne Doppler radar analyses from the Tropical Cyclone Radar Archive of Doppler Analyses with Recentering (TC‐RADAR) revealed that Quickly Aligning TCs have stronger and more compact lower‐tropospheric circulations. Although the initial vortex tilt magnitudes are similar in Quickly Aligning and Persistently Tilted TCs, Quickly Aligning storms are characterized by a tilt direction that tends to be more cyclonically downwind of the vertical wind shear vector than their Persistently Tilted counterparts. Quickly Aligning TCs also exhibit more frequent and stronger ascent in the lower troposphere than Persistently Tilted TCs, both near the lower‐tropospheric TC center and beneath the displaced mid‐tropospheric vortex, whereas differences aloft were less pronounced. The environments of Quickly Aligning TCs feature weaker mid‐tropospheric vertical wind shear, greater column‐integrated precipitable water in a mesoscale domain near the low‐level circulation center (LLC), and larger maximum potential intensities than Persistently Tilted TCs. We hypothesize that, although convection is generally favored near the mid‐tropospheric TC center, enhanced lower‐tropospheric vertical mass fluxes, especially within 35–50 km of the LLC, drive changes in misalignment via vortex stretching and precession. Plain Language Summary A key step in a tropical storm's development into a mature hurricane is when its circulation becomes vertically aligned, which is when the center of the rotation lines up with height through much of the atmosphere. However, the conditions that help storms align in the real world have not been well observed and are still not fully understood. This study uses a recently created database of airborne radar analyses to compare storms that become more vertically aligned with those that stay tilted or misaligned. We find that storms that move toward alignment generally start out with stronger, more compact low‐level circulations and have more intense and widespread thunderstorms near their centers. These Quickly Aligning storms also tend to tilt in a different direction relative to the surrounding environmental winds than storms that do not align. Together, these findings suggest that detailed observations of a storm's thunderstorm and wind structure could provide useful clues about whether a storm is likely to align vertically and, therefore, has a greater chance of strengthening. Key Points Quickly Aligning TCs have stronger and more compact lower‐tropospheric circulations than Persistently Tilted TCs Alignment is associated with stronger lower–mid‐tropospheric vertical mass fluxes near the lower‐tropospheric TC center Quickly Aligning TCs exhibit left‐of‐shear tilt orientations more often than Persistently Tilted TCs