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Large lateral variations in the depth, sharpness and magnitude of the D′′ discontinuity are observed beneath Central America and the Caribbean using a new innovative grid search modelling method. The strong correlation between the D′′ topography and the underlying seismic velocities suggest a large lateral gradient in the thermal condition in the lowermost mantle. Low velocity patches were identified amongst the high velocity areas, coinciding with regions showing a disruption in the D′′ discontinuity. The low-velocity zones may be attributed to the heat trapped in the middle of the Farallon slab remnant while those farther to the west are likely to be associated with the upwelling generated at the edge of the ancient slab. A broad range in the sharpness of the D′′ discontinuity was also observed, suggesting the existence of different chemical components in the region, as a result of a disparate mixture of basalt, harzburgite and pyrolite.