West African Heat-Low Climatology and Comparison with Dry TCs

Heat-lows are low pressure systems that have been qualitatively compared to dry tropical cyclones (TCs) given their low-level cyclonic circulation which is co-located with strong surface sensible heat fluxes. This work examines the climatology of West African heat-lows and their relationship to TCs by extending the concept of potential intensity (PI) over land. Using ERA5 reanalysis, we calculate PI over land from sensible heat flux and land surface roughness and orography data and use pre-existing data of tracked dry low-pressure systems to create composite West African heat-lows during Summer. PI spatial distribution correlates well with that of heat-low tracks and closely matches the peak heat-low wind speeds. The asymmetric and baroclinic structure of heat-low composites and the lack of marked diurnal cycles suggest that West African heat-lows are more likely analogous to TC-like baroclinic vortices such as medicanes or TCs during extratropical transition.