The Influence of Saharan Air Layers on Atlantic Basin Tropical Cyclone Intensity (1987-2008)

Investigations utilizing total precipitable water (TPW) as a proxy for Saharan air layers (SALs) in the Atlantic basin tropical cyclones (TCs) from 1987 – 2008 revealed that 44% of the 102 named storms that were in proximity to SALs at some time during their life cycles became major hurricanes. These are referred to as “SAL-interacting” major hurricanes. Since the distinctive characteristics associated with SALs are often considered unfavorable for TC genesis and intensification, this percentage is higher than expected. Analysis of other relevant data further determined that, on average, SAL-interacting major hurricanes reached their maximum intensity more than 30 hours later than non-SAL-interacting major hurricanes, which suggests that SALs at least delay TC intensification. Additional analysis will focus on incipient disturbances that became major hurricanes during this study period, including the attributes of these disturbances with and without SAL interactions (e.g., TPW, central pressure, vorticity, convection, wind speed, and protective pouches [Dunkerton, Montgomery and Wang 2008]). Concurrent large-scale environmental conditions for these disturbances will also be investigated (e.g., TPW, wind shear). Twenty-two percent of the named TCs that formed during this study period (65) became major hurricanes, which is close to climatology. Results from this study provide further evidence that SALs play an important, yet undetermined, role in Atlantic basin hurricane activity.