Abstract
AbstractDevastating Japan in October 2019, Supertyphoon (STY) Hagibis was an important typhoon in the history of the Pacific. A striking feature of Hagibis was its explosive rapid intensification (RI). In 24 h, Hagibis intensified by 100 knots (kt; 1 kt ≈ 0.51 m s−1), making it one of the fastest-intensifying typhoons ever observed. After RI, Hagibis’s intensification stalled. Using the current typhoon intensity record holder, i.e., STY Haiyan (2013), as a benchmark, this work explores the intensity evolution differences of these two high-impact STYs. We found that the extremely high prestorm sea surface temperature reaching 30.5°C, deep/warm prestorm ocean heat content reaching 160 kJ cm−2, fast forward storm motion of ∼8 m s−1, small during-storm ocean cooling effect of ∼0.5°C, significant thunderstorm activity at its center, and rapid eyewall contraction were all important contributors to Hagibis’s impressive intensification. There was 36% more air–sea flux for Hagibis’s RI than for Haiyan’s. After its spectacular RI, Hagibis’s intensification stopped, despite favorable environments. Haiyan, by contrast, continued to intensify, reaching its record-breaking intensity of 170 kt. A key finding here is the multiple pathways that storm size affected the intensity evolution for both typhoons. After RI, Hagibis experienced a major size expansion, becoming the largest typhoon on record in the Pacific. This size enlargement, combined with a reduction in storm translational speed, induced stronger ocean cooling that reduced ocean flux and hindered intensification. The large storm size also contributed to slower eyewall replacement cycles (ERCs), which prolonged the negative impact of the ERC on intensification.
Highlights
Devastating Japan in October 2019, Supertyphoon (STY) Hagibis was an important typhoon in the history of the Pacific
STY, Haiyan, which devastated the Philippines with ~6,000 deaths in 2013 (Lander et al 2014; Lin et al 2014; Mori et al 2014; Lagmay et al 2015; Huang et al 2017; Wada et al 2018; Kuo et al 2019; Tsujino and Kuo 2020). Though both are among the highest-impact category-5 STYs in the history of the Pacific and both experienced rapid intensification (RI) (Holliday and Thompson 1979; Kaplan and DeMaria 2003; Knaff et al 2018), their intensity evolution was quite different, contributing to substantially different impacts at landfall
The averaged vertical wind shear (VWS) was 7.6 (7.9) m s−1 for Hagibis (Haiyan). It appears that both cases were able to undergo RI under moderate VWS and the difference in VWS was small
Summary
Devastating Japan in October 2019, Supertyphoon (STY) Hagibis was an important typhoon in the history of the Pacific. The pre-TC SST (PI) for Haiyan was favorable, i.e., ~29°–29.5°C in Fig. 2b (~80 m s−1), though not as high as for Hagibis.
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