Impacts of the Upper-tropospheric Processes on Tropical Cyclone Formation

Dropsonde data from NASA's Global Hawks in combination with ERA-Interim reanalysis data and satellite imagery are used to examine the impacts of the upper tropospheric processes on the non-development of invest 95L/P37L during the HS3 field campaign in 2013. On September 18-20 a tropical disturbance tracked northwestward from the Caribbean Sea into the Bay of Campeche. Though tropical cyclone formation appeared imminent, the disturbance did not develop. Observational analysis shows that drying in the upper troposphere (500 hPa and above), which was accompanied by increased shear tendency and subsidence associated with upper-level ridging, suppressed convection within the wave pouch. This study suggests that persistent drying in the upper troposphere, especially when combined with certain synoptic-scale forcing, can prevent pre-conditioning of the environment for the development and organization of deep convection, which is necessary for tropical cyclone formation.