Simulation of tropical cyclones from the NASA Tropical Cloud Systems and Processes Experiment

High-resolution numerical simulations of one or two tropical cyclones during TCSP using the WRF model will be presented. In the first case, the genesis of Tropical Storm Gert is simulated. The simulation shows an easterly wave and surface trough moving westward over the southern Gulf of Mexico with somewhat disorganized convection occurring in its vicinity. Low-level easterly flow ahead of the trough impinges on the eastern side of the Sierra Madre mountains and leads to flow blocking. Because of the particular shape of the topography, this blocked flow causes northwesterly to westerly flow to occur in the southern Gulf that eventually pinches off the trough to form a closed cyclonic circulation. This topographically forced flow also helps to organize some of the convection in a linear band south of the vortex center. Once the closed cyclonic circulation is formed, convection increases and gradually intensifies the cyclone to tropical storm strength by the time of landfall.

A second case may be presented, that of Hurricane Emily. The NASA ER-2 aircraft observed intense eyewall convection when Emily was a category 4 storm and had a small radius. Did this convection represent an isolated updraft core or a ring (or partial ring) of intense upward motion. The organization of the eyewall upward motion in the simulation will be examined in order to answer this question.