Spreading of errors and GFS/GSI perturbation experiments for tropical cyclones

Sharan Majumdar
University of Miami


Tropical cyclone (TC) track forecasts are sensitive to initial perturbations in the near and far environment. Several investigations have been performed to diagnose the sensitivities for two challenging cases: Typhoon Sinlaku and Hurricane Ike (both 2008). First, the dynamical mechanisms behind the spreading of ensemble perturbations around TCs will be presented. Second, the sensitivities of the TC track forecast to direct perturbations of initial conditions in the GFS/GSI system will be reported. The results can be used to offer suggestions on ensemble forecast design, and strategies for adaptive sampling and assimilation.