The Tropical Transition in the Western North Pacific: The Case of Tropical Cyclone Peipah (2007)

Chang, Minhee; Ho, Chin Siong; Chan, Johnny C. L.; Park, Myung‐Sook; Son, Seok‐Woo; Kim, J.

doi:10.1029/2018jd029446

Cited by 10 publications

(3 citation statements)

References 53 publications

(92 reference statements)

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“…Over time, the anticyclone evolves into the upper-level trough and ridge (Figure 4). These numerical results align with the crudest feature of the formation of a cold core in the upper troposphere observed in other studies (e.g., Chang et al, 2019).…”

Section: Resultssupporting

confidence: 91%

Dynamics of localized extreme heatwaves in the mid‐latitude atmosphere: A conceptual examination

Rostami,

Severino,

Petri

et al. 2023

Atmospheric Science Letters

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This study investigates the adjustment of large‐scale localized buoyancy anomalies in mid‐latitude regions and the nonlinear evolution of associated condensation patterns in both adiabatic and moist‐convective environments. This investigation is carried out utilizing the two‐layer idealized moist‐convective thermal rotating shallow water (mcTRSW) model. Our investigation reveals that the presence of a circular positive potential temperature anomaly in the lower layer initiates an anticyclonic high‐pressure rotation, accompanied by a negative buoyancy anomaly in the upper layer, resulting in an anisotropic northeast–southwest tilted circulation of heat flux. The evolution of eddy heat fluxes, such as poleward heat flux, energy, and meridional elongation of the buoyancy field, heavily depends on the perturbation's strength, size, and vertical structure. The heatwave initiates atmospheric instability, leading to precipitation systems such as rain bands and asymmetric latent heat release due to moist convection in a diabatic environment. This creates a comma cloud pattern in the upper troposphere and a comma‐shaped buoyancy anomaly in the lower layer, accompanied by the emission of inertia gravity waves. The southern and eastern sectors of the buoyancy anomaly show an upward flux, generating a stronger cross‐equatorial flow and inertia‐gravity waves in a southward and eastward direction. Furthermore, the simulations reveal a similar asymmetric pattern of total condensed liquid water content distribution, accompanied by the intensification of moist convection as rain bands. This intensification is more pronounced in barotropic structures than in baroclinic configurations with stagnant upper layers. This study highlights the importance of considering moist convection and its effects on atmospheric and oceanic flows in mid‐latitude regions, as well as the role of buoyancy anomalies in generating heatwaves and precipitation patterns.

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Section: Resultssupporting

confidence: 91%

Dynamics of localized extreme heatwaves in the mid‐latitude atmosphere: A conceptual examination

Rostami,

Severino,

Petri

et al. 2023

Atmospheric Science Letters

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“…Moreover, Figure 4a does not show a positive zonal deviation of temperature throughout the whole tropospheric column, which is a basic characteristic of tropical cyclones (e.g. Hart, 2003; Chang et al ., 2019). Instead, there is a colder layer between 500 and 300 hPa, which is a common pattern observed in subtropical cyclones.…”

Section: Resultsmentioning

confidence: 99%

From a Shapiro–Keyser extratropical cyclone to the subtropical cyclone Raoni: An unusual winter synoptic situation over the South Atlantic Ocean

Reboita

Gozzo

Crespo

et al. 2022

Quart J Royal Meteoro Soc

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The eastern coast of South America is a cyclogenetic region in terms of extratropical cyclones and, in lower number, of subtropical cyclones that are more frequent in austral summer and autumn. However, in June 2021, an unusual cyclone developed near the boundary of Uruguay and southern Brazil, initially having extratropical features and later undergoing a subtropical transition. At 1200 UTC 29 June, the Brazilian Navy named it as subtropical cyclone Raoni. This study aims to describe the synoptic evolution of the cyclone and address physical drivers for the subtropical transition based on the ECMWF‐ERA5 reanalysis and numerical experiments with the WRF model. The cyclone precursor of Raoni had its genesis at 1800 UTC 26 June 2021 forced by a trough at mid–upper levels that crossed the Andes Mountains and caused a rapid surface pressure drop. Less than 24 hr later, the cyclone presented a frontal T‐bone pattern and warm seclusion, following the Shapiro–Keyser development model. Strong surface heat fluxes, a deep moist troposphere, and the vertical alignment of the warm seclusion with an upper‐level cut‐off pattern provided the adequate environment for organising convection and, consequently, for subtropical transition at 0600 UTC 28 June. The fundamental role of the surface turbulent heat fluxes for the transition is confirmed through numerical experiments. This study is unprecedented in the sense that no subtropical cyclone originating from a warm seclusion has been documented over the South Atlantic before. These findings emphasise the need of monitoring cold‐season extratropical Shapiro–Keyser cyclones in the region since they can evolve to a subtropical or tropical cyclone and can cause damage to the maritime activities and coastal region due to the strong winds.

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“…Iba's tropical phase is characterized by stronger maximum 10‐m winds between 18:00 UTC on 24 to 26 March and maximum total heat fluxes reaching the peak at 18:00 UTC on March 25. The intensification of near‐surface winds with a consequent increase in latent and sensible turbulent fluxes, especially over a warmer ocean (>26°C) and weaker vertical wind shear (Chang et al., 2019), is explained by the WISHE theory (Emanuel, 1986). The convection associated with the energy transfer from the ocean to the atmosphere is also revealed through the brightness temperature measured by satellite (Figures 4c–4e).…”

Section: Resultsmentioning

confidence: 99%

Iba: The First Pure Tropical Cyclogenesis Over the Western South Atlantic Ocean

et al. 2021

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Since the beginning of the satellite era, the only documented tropical cyclone over the western South Atlantic Ocean (SAO) has been Catarina, which occurred in March 2004. However, this system resulted from a tropical transition (TT), when a dipole blocking-pattern at the middle-upper levels of the atmosphere contributed to decreasing the vertical wind shear over an extratropical cyclone (McTaggart-Cowan et al., 2006; Pezza & Simmonds, 2005). Fifteen years after Catarina, in March 2019, the Brazilian Navy registered Iba, the first pure tropical cyclogenesis over tropical western SAO (∼16.5°S). Iba is an indigenous name previously established by the Brazilian Navy (NORMAN, 2018). As this system has not yet been described in the literature, it is the purpose of this study. The low frequency of tropical systems over the SAO has been explained by the unfavorable climate conditions for tropical cyclogenesis such as environmental vertical wind shear stronger than 10 m s −1 in the 850-200 hPa layer and sea surface temperature (SST) colder than 26°C (Gray, 1968; Pezza & Simmonds, 2005). On the other hand, the combination of the main environmental predictors for tropical cyclogenesis (absolute vorticity at 850 hPa, relative humidity at 700 hPa, potential intensity in terms of maximum wind speed, and the vertical wind shear at 850-200 hPa layer) in the Genesis Potential Index (GPI; K. A. Emanuel & Nolan, 2004) show some favorable conditions for tropical cyclogenesis near southeastern Brazil (Walsh et al., 2013). McTaggart-Cowan et al. (2013, 2015) also suggest that the SAO climate conditions are most likely to favor weak and strong TT than pure tropical cyclogenesis. The definition of weak and strong TT was introduced by Davis and Bosart (2003, 2004). The weak TT occurs in an environment with a weak upper-level disturbance and moderate lower-level thermal gradients, while the strong TT takes place in the presence of strong upper-level disturbance and strong lower-level thermal gradients (McTaggart-Cowan et al., 2013). Hodges et al. (2017), comparing six reanalysis datasets and IBTrACS (observed data) from 1979 to 2012, showed one tropical cyclone per year over the SAO in the observations and ∼7 cyclones per year in each

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The Tropical Transition in the Western North Pacific: The Case of Tropical Cyclone Peipah (2007)

Cited by 10 publications

References 53 publications

Dynamics of localized extreme heatwaves in the mid‐latitude atmosphere: A conceptual examination

Dynamics of localized extreme heatwaves in the mid‐latitude atmosphere: A conceptual examination

From a Shapiro–Keyser extratropical cyclone to the subtropical cyclone Raoni: An unusual winter synoptic situation over the South Atlantic Ocean

Iba: The First Pure Tropical Cyclogenesis Over the Western South Atlantic Ocean

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