Air–Sea Interaction Processes Influencing the Development of A Shapiro–Keyser Type Cyclone over the Subtropical South Atlantic Ocean

Gozzo, Luiz Felippe; Rocha, Rosmeri Porfírio da

doi:10.1007/s00024-012-0584-3

Cited by 15 publications

(16 citation statements)

References 27 publications

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“…3c). Indeed, this sensible heat flux exceeding 400 W m 22 is comparable in magnitude to the sensible heat fluxes of other rapidly developing marine cyclones from observations (e.g., Neiman et al 1990;Crescenti and Weller 1992) and model simulations (e.g., Chang et al 1996;Gozzo and da Rocha 2013). At 0000 UTC 8 December, the cyclone deepened to 953 hPa, and the maximum wind speed increased to over 40 m s 21 (Fig.…”

supporting

confidence: 62%

Using Frontogenesis to Identify Sting Jets in Extratropical Cyclones

Schultz

Sienkiewicz

2013

Weather and Forecasting

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Sting jets, or surface wind maxima at the end of bent-back fronts in Shapiro-Keyser cyclones, are one cause of strong winds in extratropical cyclones. Although previous studies identified the release of conditional symmetric instability as a cause of sting jets, the mechanism to initiate its release remains unidentified. To identify this mechanism, a case study was selected of an intense cyclone over the North Atlantic Ocean during 7-8 December 2005 that possessed a sting jet detected from the NASA Quick Scatterometer (QuikSCAT). A couplet of Petterssen frontogenesis and frontolysis occurred along the bent-back front. The direct circulation associated with the frontogenesis led to ascent within the cyclonically turning portion of the warm conveyor belt, contributing to the comma-cloud head. When the bent-back front became frontolytic, an indirect circulation associated with the frontolysis, in conjunction with alongfront cold advection, led to descent within and on the warm side of the front, bringing higher-momentum air down toward the boundary layer. Sensible heat fluxes from the ocean surface and cold-air advection destabilized the boundary layer, resulting in near-neutral static stability facilitating downward mixing. Thus, descent associated with the frontolysis reaching a near-neutral boundary layer provides a physical mechanism for sting jets, is consistent with previous studies, and synthesizes existing knowledge. Specifically, this couplet of frontogenesis and frontolysis could explain why sting jets occur at the end of the bent-back front and emerge from the cloud head, why sting jets are mesoscale phenomena, and why they only occur within Shapiro-Keyser cyclones. A larger dataset of cases is necessary to test this hypothesis.

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supporting

confidence: 62%

Using Frontogenesis to Identify Sting Jets in Extratropical Cyclones

Schultz

Sienkiewicz

2013

Weather and Forecasting

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“…Between 7 and 9 March, when Anita is approaching the south coast of Brazil, maximum winds increase throughout the atmospheric column and, at 925 hPa, peak values of ∼ 30 m s −1 occur between 0000 UTC on 8 and 9 March. Strong near‐surface winds over oceanic areas can generate high sea waves and sink boats (da Rocha et al , 2004; Gozzo and da Rocha, 2013). Prior to that, from genesis until 1200 UTC on 6 March, low‐level maximum winds remained moderate, between 10 and 15 m s −1 .…”

Section: Resultsmentioning

confidence: 99%

Structure and evolution of subtropical cyclone Anita as evaluated by heat and vorticity budgets

Dutra

Rocha

Lee

et al. 2017

Quart J Royal Meteoro Soc

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This article explores the evolution of subtropical cyclone Anita, which occurred near the east coast of Brazil (∼19°S–37°W) in March 2010. Thermodynamic and dynamic processes during Anita's life cycle are investigated using the heat and vorticity budget equations. The cyclone developed with hybrid characteristics and moved anomalously to the southwest, where it coupled with an upper‐level cut‐off low during the mature phase. This coupling was the main dynamical mechanism for further cyclone deepening. Anita then remained quasi‐stationary at about 30°S–47°W for 2 days, due to an upper‐level dipole pattern, which prevented earlier displacement of the upper‐level low counterpart. When the dipole pattern dissipated, the cyclone moved southeast and underwent extratropical transition whilst merging with a midlatitude frontal cyclone. Diabatic heating and horizontal temperature advection are found to be essential for subtropical development. During extratropical transition, instead it is diabatic cooling together with adiabatic cooling and warm‐air advection that act as the main mechanisms to influence the local temperature tendencies at low levels. Low‐level cyclonic tendencies were mostly due to convergent flow and the residual vorticity partially destroyed the vorticity tendencies produced by the divergence term. Moreover, in regions and levels where convection could explain some of the vorticity tendencies, it is found that apparent sinks of cyclonic vorticity were related to negative vorticity due to divergence (i.e. convergent flow), whilst apparent sources were related to positive vorticity due to divergence (i.e. divergent flow).

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“…This results in an increment of oceanic latent heat flux transport, facilitating the generation of deep moist convection. Several authors have tested the effects of latent heat fluxes on cyclone development (Gozzo et al, 2017; Gozzo & da Rocha, 2013; Kuo et al, 1991; Miglietta & Rotunno, 2019). However, few studies have focused on the effects of surface fluxes on the development of a Shapiro‐Keyser‐like STC.…”

Section: Introductionmentioning

confidence: 99%

Subtropical Cyclone Formation via Warm Seclusion Development: The Importance of Surface Fluxes

et al. 2020

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Subtropical cyclones (STCs) are characterized by a thermal hybrid structure with tropical and extratropical features. STCs are considered a numerical modeling challenge because of their rapid intensification. A fundamental part of their strength is derived from diabatic processes associated with convection and heat fluxes from the ocean. This study evaluates the importance of surface turbulent heat fluxes during the transition of an extratropical precursor into a STC. This cyclone evolved embedded within a strong meridional flow, having a Shapiro-Keyser structure and undergoing a warm seclusion process. To assess the importance of those heat fluxes, two Weather Research and Forecasting simulations were defined considering the presence and absence of those fluxes. Results of both simulations reveal a warm seclusion process, which weakened in absence of the heat fluxes. During the system genesis and in absence of heat fluxes, the wind and rainfall values were increased due to the remarkably intense area of frontogenesis to the northwest. Given these results and the lack of transition in the absence of heat fluxes, the frontal nature of the system was verified. Considering the heat fluxes, the obtained potential vorticity values diminished, reducing wind shear and intensifying convection in the system, which favored its transition into an STC. This study is groundbreaking in that no STC has been linked to a warm seclusion process in the Eastern North Atlantic. Additionally, simulated wind field shows an underestimation in comparison with Atmospheric Motion Vectors, used as observational data so as to give a weight to the wind analysis.

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Air–Sea Interaction Processes Influencing the Development of A Shapiro–Keyser Type Cyclone over the Subtropical South Atlantic Ocean

Cited by 15 publications

References 27 publications

Using Frontogenesis to Identify Sting Jets in Extratropical Cyclones

Using Frontogenesis to Identify Sting Jets in Extratropical Cyclones

Structure and evolution of subtropical cyclone Anita as evaluated by heat and vorticity budgets

Subtropical Cyclone Formation via Warm Seclusion Development: The Importance of Surface Fluxes

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