Thursday, 11 January 2018: 4:45 PM
Room 13AB (ACC) (Austin, Texas)
Predicting changes in tropical cyclone intensity remains a difficult challenge. To improve intensity forecasts, a deeper understanding of the impacts of environmental vertical wind shear on tropical cyclones is required. This study addresses this issue using a dataset of 20,733 dropsondes from aircraft missions occurring between 1996 and 2016 in the Pacific and Atlantic Ocean basins. Analyses show that the lower tropospheric equivalent potential temperature (θe) differences between shear-rotated quadrants become greater as shear increases. Additionally, all quadrants within the storm have decreased lower tropospheric θe in high shear cases compared to low shear cases These results suggest that in high shear cases, lower θe air is advected into the lower troposphere by downdrafts compared to low shear cases. As shear increases, mid-level relative humidity in the upshear quadrants also decreases. Prior studies have speculated that the presence of this dry air upshear may be a result of the lateral advection of environmental dry air or local subsidence. Given these findings, it is hypothesized that lowering lower tropospheric θe and decreasing mid-level relative humidity in the upshear quadrants are detrimental to the production of upshear convection. Without the development of a more symmetric precipitation distribution, tropical cyclone intensification is less likely to occur as demonstrated by prior research.
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