On the interaction of tropical‐cyclone‐scale vortices. I: Observations

Lander, Mark A.; Holland, Greg J.

doi:10.1002/qj.49711951406

Cited by 95 publications

(44 citation statements)

References 22 publications

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“…There are many documented cases of binary tropical cyclone interactions that resemble the theoretical work of Dritschel and Waugh (1992) (e.g., see Larson 1975, Lander and Holland 1993, Kuo et al 2000, Prieto et al 2003. The complete straining out regime of the binary vortex interaction in Dritschel and Waugh (1992) shows a small, weaker vortex being sheared out into thin filaments of vorticity surrounding the large, stronger vortex with no incorporation into the large vortex.…”

Section: Discussionmentioning

confidence: 89%

The Formation of Concentric Vorticity Structures in Typhoons

Kuo

Lin

Chang

et al. 2004

Journal of the Atmospheric Sciences

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An important issue in the formation of concentric eyewalls in a tropical cyclone is the development of a symmetric structure from asymmetric convection. We propose, with the aid of a nondivergent barotropic model, that concentric vorticity structures result from the interaction between a small and strong inner vortex (the tropical cyclone core) and neighboring weak vortices (the vorticity induced by the moist convection outside the central vortex of a tropical cyclone). The results highlight the pivotal role of the vorticity strength of the inner core vortex in maintaining itself, and in stretching, organizing and stabilizing the outer vorticity field.Specifically, the core vortex induces a differential rotation across the large and weak vortex to strain out the latter into a vorticity band surrounding the former. The straining out of a large, weak vortex into a concentric vorticity band can also result in the contraction of the outer tangential wind maximum. The stability of the outer band is related to the Fjørtoft sufficient condition for stability because the strong inner vortex can cause the wind at the inner edge to be stronger than the outer edge, which allows the vorticity band and therefore the concentric structure to be sustained. Moreover, the inner vortex must possess high vorticity not only to be maintained against any deformation field induced by the outer vortices but also to maintain a smaller enstrophy cascade and to resist the merger process into a monopole. The negative vorticity anomaly in the moat serves as a "shield" or a barrier to the further inward mixing the outer vorticity field. Our binary vortex experiments suggest that the formation of a concentric vorticity structure requires: 1) a very strong core vortex with a vorticity at least six times stronger than the neighboring vortices, 2) a large neighboring vorticity area that is larger than the core vortex, and 3) a separation distance between the neighboring vorticity field and the core vortex that is within three to four times the core vortex radius.2

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Section: Discussionmentioning

confidence: 89%

The Formation of Concentric Vorticity Structures in Typhoons

Kuo

Lin

Chang

et al. 2004

Journal of the Atmospheric Sciences

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“…These situations occur more frequently in the western and eastern North Pacific [Ramage, 1972;Lander and Holland, 1993]. Several hurricanes sometimes develop simultaneously over the Atlantic Ocean, too, as was observed, for example, in August 1995.…”

Section: Introductionmentioning

confidence: 77%

“…During the mutual approach, one member of the interacting pair usually decays and loses its identity at relatively large distances (of the order of several hundred kilometers) from the surviving (winner) vortex. In other cases, however, attraction of binary storms may sharply change to repulsion after a certain separation distance is reached [Lander and Holland, 1993]. Thus different scenarios are experimental design are presented in section 3.…”

Section: Introductionmentioning

confidence: 99%

Interaction of binary tropical cyclones in a coupled tropical cyclone‐ocean model

Хаин¹,

Ginis²,

Falkovich³

et al. 2000

J. Geophys. Res.

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Abstract. The motion and evolution of binary tropical cyclones was investigated using a coupled tropical cyclone-ocean movable nested grid model. The model consists of eight-layer atmospheric and seven-layer ocean primitive equation models. Several regimes of binary storm interaction have been identified, depending on the initial separation distance (a) and differences in storm strengths. At d less than a few hundred kilometers, interacting storms experienced complete merger (CM) or partial merger (PM). At larger d (between about 600 km and 1000 km), three regimes of storm interaction have been found: PM, straining out (SO), characterized by complete disintegration of the weaker storm, and mutual straining out (MSO), characterized by weakening and dissipation of both storms. SO occurred when the interacting storms had substantially different intensities and strengths. MSO was observed when the interacting storms were comparable in size and intensity. In the latter case the storms were unable to approach each other at distances smaller than a certain minimum distance (of about 450-500 km) without being mutually stretched out. Moreover, initial attraction of the storms in this regime was replaced by repulsion, as frequently observed in the western Pacific. At d exceeding about 1000 km, elastic interaction (EI) was found, when the storms interact without any significant changes in their intensity and structure. In additional experiments with a conditional instability of the second kind (CISK) type parameterization of convective heating the storm interaction was very different: The storms were nearly axisymmetric and very compact, and they continued approaching each other until they merged. Thus more realistic simulations of binary storm interaction can be achieved by using a physically more reasonable convective parameterization.

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“…At the same time, another weaker typhoon, Goni, formed at 1200 UTC 03 August, circled cyclonically over the Hainan Island region. There seems to be a Fujiwhara effect (Lander and Holland 1993;Wu et al 2003) between these two typhoons. Goni eventually weakened mostly due to the intense environmental vertical shear over the northern South China Sea.…”

Section: Overview Of Typhoon Morakotmentioning

confidence: 91%

Rainfall Simulations of Typhoon Morakot with Controlled Translation Speed Based on EnKF Data Assimilation

Yen¹,

Lien³

2011

Terr. Atmos. Ocean. Sci.

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Typhoon Morakot produced record-breaking accumulated rainfall over southern Taiwan in August 2009. The combination of several factors resulted in this extreme weather event: the steep terrain in Taiwan, the prevailing south-westerly flow in the monsoon trough, Typhoon Goni over the northern South China Sea, and the slow translation speed of Morakot itself over Taiwan. In this study, the influence of the translation speed is particularly emphasized. Based on the EnKF data assimilation, an innovative method is applied to perform ensemble simulations with several designated translation speeds of Morakot using the WRF model. Thus the influence of the translation speed on the amount of accumulated rainfall over Taiwan can be quantitatively evaluated. In the control simulation with observed translation speed, the maximum amount and geographic pattern of accumulated rainfall during the landfall period of Morakot are generally consistent with the observations, though the detailed overall distributions of accumulated rainfall is mostly underestimated, resulting in the low bias of the frequency distribution of the accumulated rainfall. In a simulation with nearly-doubled translation speed of Morakot, the maximum accumulated rainfall is decreased by 33% than that in the control simulation, while the rainfall distribution over Taiwan remains similar. In addition, the 28 ensemble members can further provide additional information in terms of their spread and other statistics. The results from ensemble members reveal the usefulness of ensemble simulations for the quantitative precipitation forecast.

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On the interaction of tropical‐cyclone‐scale vortices. I: Observations

Cited by 95 publications

References 22 publications

The Formation of Concentric Vorticity Structures in Typhoons

The Formation of Concentric Vorticity Structures in Typhoons

Interaction of binary tropical cyclones in a coupled tropical cyclone‐ocean model

Rainfall Simulations of Typhoon Morakot with Controlled Translation Speed Based on EnKF Data Assimilation

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