The WRF high-resolution regional model has been applied in this study as an effort to better understand the physical processes that governed the genesis of the 2004 Hurricane Danielle from an African easterly wave (AEW). In addition, the WRF model skill in predicting the structure, the time, location and intensity of the cyclogenesis is examined at 4.5 days and 2.5 days forecast periods prior to development and with various cumulus parameterizations schemes. Results obtained by the 2.5 days forecast period ahead of the tropical depression (TD) stage were able to simulate the cyclogenesis with an excellent performance in the sea level pressure (SLP) and maximum winds. The tropical storm (TS) stage of Hurricane Danielle was also forecasted by the model, though more intense and 6 hour prior to the NHC estimates.

Based on the forecasted 700 hPa streamlines and 850 hPa relative vorticity, a correlation could be established with the forecasted accumulated precipitation relative to the AEW location since the beginning of each simulation. Cyclonic relative vorticity responded to the mesoscale convective systems (MCS) intensity changes indicating that precipitation by MCS played a role in the strengthening and weakening of the AEW associated with Hurricane Danielle. Over the African continent, reduction in the rainfall amount is attributed to the possible advection of dry air by north-northeasterly flow. However, redevelopment and amplification of precipitation is mostly attributed to moisture entrainment from the Gulf of Guinea by the southerly flow and also by the effects of orography. Even though a delay in the time that the AEW was expected to come off the African coast was forecasted by all the simulations, the westward moving convective pattern associated with the Hurricane Danielle precursor observed in the Meteosat-7 infrared (IR) satellite observations was captured by the simulations, in particular by those that were able to forecast cyclogenesis.