What Convective Properties Are Most Critical for Tropical Cyclogenesis? Evidence from Multi-satellite Observations of Genesis Cases Investigated During Recent Field Programs

Though deep convection has invariably been identified as an important component of tropical cyclogenesis, the specific properties of convective systems necessary for genesis continue to be contended. While some studies have identified the aggregation of intense vortical hot towers as an essential building block in genesis, others have argued that the areal coverage of precipitation around the disturbance center is more important than convective intensity. Likewise, although the properties of convection at, and just prior to, genesis are often well documented, the characteristics of convective events multiple days prior to formation, and their importance for modifying the inner core wind and thermodynamic structure, have received less attention. Given the recent emphasis on tropical cyclogenesis by multiple field programs (including NOAA IFEX [since 2005], NASA GRIP [2010], NSF/NCAR PREDICT [2010], and NRL TCS-08), opportunities exist to examine not only the wind and thermodynamic properties of the pre-cursor tropical wave, but also the time evolution of the associated deep convective events multiple days before genesis. This study will specifically examine satellite data compiled for a number of genesis cases investigated by field programs since 2005; satellites include conventional geostationary IR, as well multiple passive microwave platforms, such as TRMM, AMSR-E, SSM-I/S and AIRS. By evaluating proxies for convective intensity, raining area and proximity to the disturbance center, analysis from multiple detailed case studies may lend support to the hypothesis that the fractional coverage of precipitation near the center - not necessarily intensity - is most critical for genesis to occur, while also offer insight into whether particular convective properties differentiate disturbances that, once the large-scale environment is favorable, form "quickly" (after 1-2 convective burst periods), versus disturbances that go through multiple convective events prior to formation. Likewise, by synthesizing information on the time evolution of convective properties with quantitative measurements of moisture content (derived from dropsondes and passive microwave satellite data), a specific emphasis is placed on critically evaluating the hypothesis that deep convection is responsible for the progressive moistening of the inner core of the developing disturbance.