Speaker: Pete Finocchio (U of Miami)
Topic: "The Structure of Vertical Wind Shear in Tropical Cyclone Environments: Implications for Intensity Forecasting and Predictability"
Room: 529 Walker Building (refreshments served)
Time: Thursday October 20, 2016 10:30am to 11:30am
Abstract: Several modeling studies have investigated how environmental vertical wind shear affects tropical cyclone (TC) intensity prediction by varying the magnitude or direction of the deep- layer (200-850 hPa) shear. But in a series of idealized simulations, we found that environments with the same deep-layer shear engender vastly different TC evolutions depending on how the shear is vertically distributed. Our simulations showed that shallow layers of vertical wind shear that are concentrated lower in the troposphere are more destructive than shear concentrated higher in the troposphere. This response owes to more effective boundary layer flushing under low-level shear. In order to determine whether this new aspect of the environmental wind profile is worth incorporating into statistical intensity prediction schemes, we developed new parameters describing the height and depth of vertical wind shear in real TC environments. To our surprise, we found very weak correlations between these parameters and the intensity changes of a large sample of Northern Hemisphere TCs. We attributed these weak relationships partly to an observed tendency for other aspects of the TC environment to become less favorable for intensification when the parameters attain values that should be more favorable for intensification. A new study is underway that uses ensembles of simulations initialized with realistic environmental wind profiles to understand how the height and depth of vertical wind shear affect a TC’s intrinsic predictability.