Evaluating Environmental Favorableness for Tropical Cyclone Development with the Method of Point-Downscaling

Abstract

A new method is presented to determine the favorableness for tropicalcyclone development of an atmospheric environment, as represented by amean sounding of temperature, humidity, and wind as a function ofheight. A mesoscale model with nested, moving grids is used to simulatethe evolution of a weak, precursor vortex in a large domain with doublyperiodic boundary conditions. The equations of motion are modified tomaintain arbitrary profiles of both zonal and meridional wind as afunction of height, without the necessary large-scale temperaturegradients that cannot be consistent with doubly periodic boundaryconditions. Comparisons between simulations using the point-downscalingmethod and simulations using wind shear balanced by temperaturegradients illustrate both the advantages and the limitations of thetechnique. Further examples of what can be learned with this method arepresented using both idealized and observed soundings and wind profiles.