Abstract
As a category-3 typhoon, Hato (2017) experienced the notable rapid intensification (RI) over the hot sea surface before its landfall. The RI process and the influences of local sea surface temperature (SST) patterns on the evolution of Hato were well captured and carefully investigated using a high-resolution air–sea coupled model. To further explore the close relationship between the radial distributions of SST and storm evolution, a sensitive experiment with time-fixed SST was also performed. Results showed that the time-fixed SST experiment produced earlier RI following the rapid core structure adjustment, as higher SST in the core region was found favorable to increasing the near-surface water vapor and latent heat flux. Strong updrafts were thus facilitated inside the eyewall, inducing the eyewall contraction and RI of the storm. In contrast, cooler SST inside the core region should account for the delay of RI as the intense convection located in the outer rainbands, inhibiting the transportation of energy into the inner-core. Momentum tendency analysis also proves these mechanisms. Therefore, not only the value of SST but also its radial-gradient, plays an important role in the evolution of tropical cyclones, highlighting the need for an advanced air–sea coupled model.
Highlights
Tropical cyclone (TC) is a severe weather phenomenon generating on the warm low-latitude ocean surface that brings much damages and increasing economic losses to the coastal areas every year
E, 22.1◦ N) at 0450 UTC on 23 August with the 10-m wind speed reached to 51.7 m s−1 and the central pressure of 948 hPa
Results suggest that warmer sea surface temperature (SST) outside the radius of the maximum wind (RMW) induce secondary updrafts that lead to the delayed onset of rapid intensification (RI)
Summary
Tropical cyclone (TC) is a severe weather phenomenon generating on the warm low-latitude ocean surface that brings much damages and increasing economic losses to the coastal areas every year. Comparing with the increasing capability of the track forecast, the prediction ability for TC intensity has rarely been improved in the recent 30 years [1,2,3,4], especially for the rapidly intensifying TCs over warm oceanic features [5,6,7,8,9,10,11,12]. Sea surface temperature (SST) distributions under the storm is among the key factors impacting the evolution of TCs [17,18]. High SST benefits the intensification and maintenance of TCs by offering abundant surface moist enthalpy fluxes to the atmosphere.
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