Diurnal Variations in Contraction of the Radius of Maximum Tangential Wind in Tropical Cyclones

Diurnal variations in contraction of the radius of maximum tangential wind (RMW) of tropical cyclones (TCs) were assessed using best-track data for 2001-2018. For RMW contractions before TC intensification, the largest RMW contraction rate in 6 hr at 0300-0900 local solar time (LST) was associated with the maximum coverage of very deep convective clouds with infrared brightness temperatures <208 K at 0300-0600 LST, which were found mostly outside the mean RMW. The maximum RMW contraction rate and maximum intensification rate occurred simultaneously in 6 hr at 0300-0900 LST for rapidly intensifying storms associated with the greatest coverage of very deep convective cloud at 0300-0600 LST at storm center. This was not the case for nonrapidly intensifying storms. The time-dependence of RMW contraction indicates the importance of radiative forcing on TC structure.