The effects of moist entropy and moisture budgets on tropical cyclone development

This paper examines the moist entropy and moisture budgets in tropical cyclones, as well as their relation to tropical cyclone's development. This analysis focuses on the dropsonde data collected during Hurricane and Severe Storm Sentinel project and the accompanying satellite data. Two tropical cyclones of interest are Tropical Storm Gabrielle (2013) and Hurricane Edouard (2014). There were three research flights into Gabrielle (2013), during its nondeveloping and decaying stages. Edouard (2014) was visited four times in different stages of its life cycle, twice during the intensification and twice during the decay. Also, we extended our analysis on the larger data set, consisting of 11 nonintensifying and 12 intensifying systems. Our study shows that the moist entropy tends to increase during intensification and decrease during nonintensifying stages. On the other hand, the moisture budget relates better to the tropical cyclone's current intensity than its development. The sign of the moist entropy tendency depends on the ability of surface fluxes and irreversible moist entropy generation to overcome lateral export of moist entropy and loss due to radiative cooling. Edouard's decay during the last research flight was likely the result of increasing wind shear and low sea surface temperatures. During its decay, Gabrielle had strong column‐integrated lateral export of moist entropy and drying between 1 and 4 km height. This is probably the consequence of a dry environment at multiple levels, amplified by a warm and dry anomaly left behind by previous convective activity. Key Points Moist entropy budget can possibly be used to differentiate between intensifying and nonintensifying tropical cyclones Moisture tendency relates to current intensity of a tropical cyclone, with higher values for stronger tropical cyclones Relationships between the thermodynamic budgets and TC development derived from the observational data