A spatio-temporal comparison of moisture environments associated with North Atlantic and eastern North Pacific hurricanes

Tropical cyclones (TCs) tend to exist within atmospheric environments characterized by an asymmetric distribution of moisture. However, the TC response to the surrounding moisture pattern depends on many factors including their structure and environmental vertical wind shear. Mature TCs, here defined as storms with maximum sustained winds of at least 65 kt, are explored during the period 2000-2022 to overlap with the TRMM-GPM satellite era and wider availability of scatterometer observations. Samples are limited to events with low-to-moderate vertical wind shear (≤ 20 kt) while over the ocean.

For the North Atlantic, ERA5-based TC size estimates corroborate past research showing that more moist environments are conducive to larger and stronger TCs. However, the moisture pattern—specifically, the spatial location of moisture relative to the TC—appears to be relevant to the TC’s future behavior, providing physical context beyond area-averaged values. These findings also indicate that TC size may affect the potential for and timing of mid-level ventilation when regions of dry air exist near the TC. Since work thus far has focused on the North Atlantic, this presentation will also discuss the dominant moisture patterns of mature eastern North Pacific (ENP) TCs and compare them to the patterns found for mature North Atlantic TCs. Since vertical wind shear, on average, tends to be weaker for these ENP TCs, differences in shear between cases in the two basins will also be explored. Beyond sharing the study results, this presentation will provide links to relevant Python code examples on GitHub.