On 23 August, 2017, Typhoon Hato rapidly intensified by 10 kt within 3 h just prior to landfall in the city of Macau along the South China coast. Hato’s surface winds in excess of 50 m s⁻¹ devastated the city, causing unprecedented damage and social impact. This study reveals that anomalously warm ocean conditions in the nearshore shallow water (depth < 30 m) likely played a key role in Hato’s fast intensification. In particular, cooling of the sea surface temperature (SST) generated by Hato at the critical landfall point was estimated to be only 0.1–0.5 °C. The results from both a simple ocean mixing scheme and full dynamical ocean model indicate that SST cooling was minimized in the shallow coastal waters due to a lack of cool water at depth. Given the nearly invariant SST in the coastal waters, we estimate a large amount of heat flux, i.e., 1.9k W m⁻², during the landfall period. Experiments indicate that in the absence of shallow bathymetry, and thus, if nominal cool water had been available for vertical mixing, the SST cooling would have been enhanced from 0.1 °C to 1.4 °C, and sea to air heat flux reduced by about a quarter. Numerical simulations with an atmospheric model suggest that the intensity of Hato was very sensitive to air-sea heat flux in the coastal region, indicating the critical importance of coastal ocean hydrography.

Tropical cyclone (TC) translation speed is an important parameter. In the context of TC–ocean interaction, faster translation speed can contribute to less TC-induced ocean cooling and thus enables more air–sea enthalpy flux supply to favor TC intensification. In 2018, Kossin published an interesting paper in Nature, reporting a global slow-down of TC translation speed since the 1950s. However, upon close inspection, in the last two decades, TC translation speed actually increased over the western North Pacific (WNP) and neighboring seas. Thus, we are interested to see which sub-region in the WNP and neighboring seas had the largest increase during the last two decades, and whether such increases contribute to TC intensification. Our results found statistically significant translation speed increases (~0.8 ms⁻¹ per decade) over the South China Sea. Ruling out other possible factors that may influence TC intensity (i.e., changes in atmospheric vertical wind shear, pre-TC sea surface temperature or subsurface thermal condition), we suggest, in this research, the possible contribution of TC translation speed increases to the observed TC intensity increases over the South China Sea in the last two decades (1998–2017).

Hurricane Patricia formed on 20 October 2015 in the Eastern Pacific and, in less than 3 days, rapidly intensified from a Tropical Storm to a record‐breaking hurricane with maximum sustained winds measured around 185 knots. It is almost 15 knots higher than 2013's supertyphoon Haiyan (the previous strongest tropical cyclone (TC) ever observed). This research focuses on analyzing the air‐sea enthalpy flux conditions that contributed to Hurricane Patricia's rapid intensification, and comparing them to supertyphoon Haiyan's. Despite a stronger cooling effect, a higher enthalpy flux supply is found during Patricia, in particular due to warmer pre‐TC sea surface temperature conditions. This resulted in larger temperature and humidity differences at the air‐sea interface, contributing to larger air‐sea enthalpy heat fluxes available for Patricia's growth (24% more than for Haiyan). In addition, air‐sea fluxes simulations were performed for Hurricane Patricia under different climate conditions to assess specifically the impact of local and large‐scale conditions on storm intensification associated with six different phases and types of El Niño Southern Oscillation (ENSO) and long‐term climatological summer condition. We found that the Eastern Pacific El Niño developing and decaying summers, and the Central Pacific El Niño developing summer are the three most favorable ENSO conditions for storm intensification. This still represents a 37% smaller flux supply than in October 2015, suggesting that Patricia extraordinary growth is not achievable under any of these typical ENSO conditions but rather the result of the exceptional environmental conditions associated with the buildup of the strongest El Niño ever recorded.

Devastating 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 RI (rapid intensification). In 24 h, Hagibis intensified by 100 kt, 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 2 high-impact STYs.We found that the extremely high pre-storm sea surface temperature reaching 30.5∘C, deep/warm pre-storm 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.