A 3-DIMENSIONAL ANALYSIS OF THE OUTFLOW LAYER OF SUPERTYPHOON FLO (1990)

Isentropic coordinate analyses of rawinsondes and cloud motion wind ve ctors derived from geostationary satellite imagery are employed to des cribe the three-dimensional upper-tropospheric and lower-stratospheric circulation attending western North Pacific Supertyphoon Flo during S eptember 1990. Outflow from the storm is concentrated in several evolv ing channels in the horizontal. In terms of vertical structure, net ou tflow evaluated at 6 degrees latitude (666 km) radius is found to occu r at higher levels and over an increasing range of potential temperatu re theta as the tropical cyclone intensifies. Outflow on the equatorwa rd side of the tropical cyclone tends to occur at greater theta values (higher altitudes) than poleward outflow. Potential vorticity also de creases within the corresponding isentropic layers associated with the outflow. The implications of the vertical variability of outflow stru cture in terms of the interactions between storm and environment, and effects on storm structural changes, are considered briefly.