A Multisatellite Investigation of the Convective Properties of Developing and Nondeveloping Tropical Disturbances

Abstract

comprehensive passive microwave satellite dataset is analyzed to quantify and compare the time evolution of convective properties of the pregenesis stage of developing disturbances (12 cases) and nondeveloping disturbances (3 cases), to determine whether the properties within the day prior to formation are unique, and to determine whether there is a credible connection between convection and the organization of the incipient circulation. Cases examined were the focus of recent (since 2005) field programs, and include those investigated during the triagency field programs in the Atlantic during 2010 [NASA?s Genesis and Rapid Intensification Processes (GRIP) project, the National Science Foundation (NSF)/NCAR Pre-Depression Investigation of Cloud-Systems in the Tropics (PREDICT) program, and NOAA?s Intensity Forecasting Experiment (IFEX)]. Among the properties examined (raining area, intensity, areal coverage of ?strong? and ?intense? convection, frequency, and proximity to the disturbance center), the results indicate that the area and frequency of rainfall within 3° are distinguishably greater in developing disturbances. Except for the fact it occurs in a more organized disturbance, there does not appear to be anything special about strong [polarization corrected temperature (PCT) ≤ 210 K] or intense (PCT ≤ 160 K) convection occurring in the day before genesis. Strong and intense convection events are observed throughout the pregenesis stage, do not necessarily increase (in intensity and area) as genesis nears, and are not necessarily very close (within 1°) to the center within a day of genesis. Likewise, while the areal coverage of strong and intense convection during the pregenesis stage is typically greater in developing disturbances, the overall intensity of convection in nondeveloping disturbances is comparable to the developing cases examined.