Convective Evolution during Tropical Cyclone Formation as Revealed by TRMM PR

Abstract:

To understand the convective evolution during tropical cyclone formation, cloud features for more than 200 named tropical cyclones over the Atlantic and East Pacific are examined from the tropical wave to the tropical cyclone stage using the TRMM Precipitation Radar (PR). The echo top height of the 20-dBZ radar reflectivity is used in combination with the near surface rain rate to identify the different types of convection: i) shallow cumuli; ii) cumulus congestus and iii) deep convection. The frequency of occurrence for each convective type is calculated 24, 48 and 72 hours before genesis, and the relative contributions of different types of convection to the total rain rate are examined at various radii with respect to the pouch center. The implication of these findings for a recently proposed conceptual model for tropical cyclone formation will be discussed.