The Llanos low-level jet and its association with Venezuelan convective precipitation

Low-level jets play an important role in transporting moisture and heat from one location to another. The NCEP North American Regional Reanalysis indicates the existence of a nocturnal low-level jet over the central Venezuelan plains, known as the Llanos, during the austral summer. Pilot balloon observations taken at San Fernando de Apure, Venezuela are used to validate the reanalysis data and verify the time of year and altitude at which upper-air Llanos wind speeds are greatest. Vertical profiles of pilot balloon-observed and regional reanalysis-estimated wind speeds during the dry and wet seasons of 2001 to 2004 show good agreement. Deep convection was expected to occur near the exit region of the Llanos low-level jet, close to the average position of the intertropical convergence zone during the austral winter. Cloud-top temperature frequency composites of northern South America during strong and weak low-level jet events in the dry and wet seasons are constructed to show that a strong Llanos jet is associated with deep convection in the southern Llanos.