3:00 PM - 3:15 PM
[AAS02-12] Re-intensification of seafalling tropical cyclones
Keywords:tropical cyclone, seafall, re-intensification, simulation
After making landfall, a tropical cyclone (TC) is cut off from the supply of heat and moisture from the ocean and experiences increased surface friction, generally leading to its weakening (Chen & Chavas 2020, 2021, 2023, Phillipson & Toumi 2021, Sparks & Toumi 2022, Hlywiak & Nolan 2021, Takahashi & Nolan 2024, Takahashi et al. 2024). However, if such a perturbed system then re-enters the ocean (hereafter seafall), it can re-intensify. In fact, TCs in the western North Pacific and North Atlantic basins often pass over land and re-intensify over the ocean before making another landfall. For example, Typhoon Noru (2022) passed through Luzon Island before making landfall at Da Nang, Vietnam; Hurricane Ian (2022) passed through Cuba and then Florida before making its third and final landfall at Georgetown, South Carolina. They both re-intensified upon seafall (Wei et al. 2024, Heidarzadeh et al. 2023).
The study of TCs making seafall has been limited. There are a handful of studies on the statistics of seafalling TCs in the western North Pacific. Brand & Blelloch (1973) and Brand & Blelloch (1974) are the first studies on seafalling TCs crossing the Philippines and Taiwan, respectively. They focused exclusively on the changes of TC characteristics such as intensity, size, translation speed, and track before and after passage over land. These statistics, while somewhat helpful for the operational forecaster, provide little insight regarding the physical processes driving the structural evolution and re-intensification of seafalling TCs.
The only mechanism proposed for the re-intensification of seafalling TCs is that of land-induced eyewall replacement as part of the following case studies by full simulation: Typhoon Zeb (1998) crossing the Philippines (Wu et al. 2009, 2003), Typhoon Megi (2010) crossing the Philippines (Wang & Wang 2014, 2021), Typhoon Fanapi (2010) crossing Taiwan (Yang et al. 2018), and Typhoon Mangkhut (2018) crossing the Philippines (Lau et al. 2024). However, only 57% of the TCs that cross the Philippines experience land-induced eyewall replacement, and the figure is even lower for TCs that cross Taiwan (Chou et al. 2011).
It is therefore important to establish the general processes of TC seafall re-intensification. A clear understanding of the physics behind and the associated structural evolution of seafalling TCs is a first step to allow for better predictions of their behaviour leading up to the second landfall, and could aid operational forecast and risk mitigation efforts.
Here, idealised simulations are used to study the re-intensification of seafalling TCs. They follow a two-stage fast-slow process driven predominately by a change in surface friction initially and then by heating. The previous land decay causes seafalling TCs to be larger and intensify more slowly with milder inner-core contraction than in ocean-only cases. Nonetheless, they reach the same intensity but with almost twice the integrated kinetic energy, so that the second landfall made by seafalling TCs can cause more damage and greater economic impact due to their larger footprint of destructive wind compared with ocean-only cases, even before they are fully re-developed.
The study of TCs making seafall has been limited. There are a handful of studies on the statistics of seafalling TCs in the western North Pacific. Brand & Blelloch (1973) and Brand & Blelloch (1974) are the first studies on seafalling TCs crossing the Philippines and Taiwan, respectively. They focused exclusively on the changes of TC characteristics such as intensity, size, translation speed, and track before and after passage over land. These statistics, while somewhat helpful for the operational forecaster, provide little insight regarding the physical processes driving the structural evolution and re-intensification of seafalling TCs.
The only mechanism proposed for the re-intensification of seafalling TCs is that of land-induced eyewall replacement as part of the following case studies by full simulation: Typhoon Zeb (1998) crossing the Philippines (Wu et al. 2009, 2003), Typhoon Megi (2010) crossing the Philippines (Wang & Wang 2014, 2021), Typhoon Fanapi (2010) crossing Taiwan (Yang et al. 2018), and Typhoon Mangkhut (2018) crossing the Philippines (Lau et al. 2024). However, only 57% of the TCs that cross the Philippines experience land-induced eyewall replacement, and the figure is even lower for TCs that cross Taiwan (Chou et al. 2011).
It is therefore important to establish the general processes of TC seafall re-intensification. A clear understanding of the physics behind and the associated structural evolution of seafalling TCs is a first step to allow for better predictions of their behaviour leading up to the second landfall, and could aid operational forecast and risk mitigation efforts.
Here, idealised simulations are used to study the re-intensification of seafalling TCs. They follow a two-stage fast-slow process driven predominately by a change in surface friction initially and then by heating. The previous land decay causes seafalling TCs to be larger and intensify more slowly with milder inner-core contraction than in ocean-only cases. Nonetheless, they reach the same intensity but with almost twice the integrated kinetic energy, so that the second landfall made by seafalling TCs can cause more damage and greater economic impact due to their larger footprint of destructive wind compared with ocean-only cases, even before they are fully re-developed.