The strength of a hurricane's upper-level cyclonic outflow is a strong indicator of the cyclone's current intensity and its prospects for near future intensification. Tangential winds blowing outward from the hurricane's eyewall cloud at levels of 150-250 mb can often be 60-80 percent as strong as are the low-level inflowing tangential winds at the same radius. Such high tangential wind outflow to inflow ratios can occur only with strong eyewall mass flux and an inner-core transverse circulation which is substantially stronger than that specified by low-level frictionally forced convergence. Thermal wind considerations dictate that high values of this tangential wind inflow/outflow ratio indicate that the cyclone's inward radial warming be more concentrated at upper rather than lower levels. This acts to enhance wall-cloud convective buoyancy and net wall cloud vertical motion.
The ratio of the eyewall clouds tangential wind outflow to inflow is thus a very important proxy signal for specifying the wall clouds's thermal buoyancy and strength of the inner-core transverse circulation and the amount of effective vertical wind shear and ventilation which is occurring near the cyclone's center.
The new one-minute wind SMS satellite-loop data and upper level reconnaissance jet of NOAA will have the potential to directly measure the strength of a hurricane's inner-core tangential winds in the outflow levels. This new measurement should help in diagnosing and short term prediction of intensity change.