Upper-Tropospheric Forcing of the Intensification Rates of Tropical Cyclones Flo and Ed Based on TCM-90 Observations
NAVAL POSTGRADUATE SCHOOL MONTEREY CA
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A case study of the upper-tropospheric forcing of the intensification rates of typhoons Flo and Ed has been accomplished. High-resolution, hand-drawn streamline analyses of the 150, 200, 250, and 300 mb winds from the final observational data set of the Tropical Cyclone Motion TCM-90 field experiment were constructed for 00, 06, 12, and 18 UTC during the period 00 UTC 12 September through 00 UTC 19 September 1990. Three basic interaction mechanisms that appeared to have major roles in upper-level forcing on Flo and Ed were defined. Outflow layer changes were quantified through calculation of the mass divergence and eddy flux convergence of relative angular momentum using a radial-band averaging technique at 200 mb. A nearly 11 qualitative relationship was found to exist between the development of one or more of these massheat export mechanisms and corresponding changes in the intensification rates. These calculations from the best-ever typhoon region data set strongly suggest that upper-level forcing leads the intensification process by 12-24 h.