Understanding What can be Resolved with Polar-Orbiting Satellite Platforms for Fast Evolving Tropical Convective Systems

It is critical to understand and resolve the dynamics of mesoscale convective systems (MCSs) that initiate over the West African continent. For example, during the 2013 Atlantic hurricane season, there was no lack of African Easterly Waves (AEWs) generating MCSs over the Sahel region. Both the GFS and ECMWF models favored development of these waves into tropical cyclones while the AEWs were still over land, however the systems failed to develop once over the Eastern Atlantic. The transition between continental MCSs and tropical cyclogenesis off the coast of West Africa is rarely observed with radars that provide high spatial resolution on the vertical structure. The NASA African Monsoon Multidisciplinary Analyses (NAMMA) field campaign, which took place from 15 August through 30 September 2006, was based in the Cape Verde Islands and Dakar, Senegal, which is the westernmost point of West Africa. During the experiment, surface observation networks and aircraft characterized the evolution and structure of AEWs and MCSs over land in West Africa to maritime environments in the Eastern Atlantic. A thirteen-year (2000-2013) climatology of PR data was used to construct CFADs of three regimes (continental, transition, and oceanic) in the region of West Africa and the Eastern Atlantic. The climatology of thirteen years of TRMM data shows evidence of maximum heights reached between MCSs that exist over continental West Africa are an average of up to 4 km taller than maximum heights reached by MCSs over the adjacent Eastern Atlantic. To quantify the differences between TRMM PR and ground-based radar, the evolution of 3 strong MCS cases (31 August, 2 September, and 11 September 2006) were examined using data from the NASA Polarimetric (NPOL) radar. The NPOL observations are the first ground-based radar analyses to show consistent agreement with previous studies of transitioning MCSs using TRMM data, with the added benefit of showing collapse occurring within 3 hours of exiting the coast. The results of this work suggest that it is important to have ground-based radar data along the coast of West Africa upstream from the Cape Verde islands to better initialize forecasting models.