Humidity Evolution Observed during Tropical Cyclogenesis and its Difference Compared to Nondeveloping Disturbances

This study contributes to a global survey of the environmental properties of developing and nondeveloping tropical disturbances, with a focus on distinguishing the moisture and relative humidity evolution of those disturbances that develop into tropical cyclones (TCs) from those that do not develop. Moisture and humidity properties are quantified using an accumulation of overpasses of the NASA Atmospheric Infrared Sounder (AIRS). The overpasses are subset for disturbance tracks in the Tropical Cyclone - Passive Microwave (TC-PMW) dataset that encompasses all stages of the TC life cycle. The TC-PMW consists of 13 years (2003-2015) of tracks of pre-genesis and nondeveloping disturbances globally (the North Atlantic, East Pacific, Central Pacific, West Pacific, northern Indian Ocean, southern Indian Ocean, and South Pacific basins). Nondeveloping disturbances are defined as those disturbances that do not exceed an "invest" classification by the operational centers (NHC, CPHC, and JTWC). Overall, this study will offer a detailed analysis of the environmental humidity properties multiple days before genesis, compare those properties to those of nondeveloping disturbances, and relate the evolution of humidity with the observed precipitation properties already quantified from passive microwave overpasses subset for tracks in the TC-PMW. These analyses present an opportunity to determine how precipitation and the moisture/relative humidity evolutions are related, and whether moisture/relative humidity properties can be used to quantify the probability that a disturbance could undergo tropical cyclogenesis. The study will also investigate whether there are characteristic humidity differences among the basins.