High-resolution simulation of the genesis of Hurricane Danielle (2004)

The African Easterly Waves (AEWs) are important precursors for the generation of Atlantic major hurricanes. This study focuses on the transition phase from the AEWs to Hurricane Danielle in 2004. Observational analysis indicates that abnormal Sea Surface Temperature (SST) over tropical east Atlantic was associated with the genesis and early development of Hurricane Danielle. The corresponding atmospheric circulation was characterized by positive westerly anomalies over the lower troposphere in response to positive SST anomalies (anomalous downwelling) centered around 10°N over the eastern sector of the tropical Atlantic Ocean. Numerical experiments further show that SST anomalies over the tropical eastern Atlantic basin can alter the supply of moisture to West Africa and influence Hurricane development. Strong (weak) westerly anomalies support increased (reduced) transport of moisture into the region. Therefore, convective activity is enhanced (reduced) when AEWs and Mesoscale Convective Systems (MCSs) propagate through the region. Increased convective activity is favorable for the formation and evolution of tropical cyclones. The simulation of the early life cycle of Hurricane Danielle in 2004 over the east Atlantic Ocean basin also suggests that the moisture simulated by the model can significantly impact the development of tropical cyclones from the AEWs as they move off the West Africa coast.