A Lagrangian analysis of a developing and non-developing disturbance observed during the PREDICT experiment

Rutherford, Blake; Montgomery, Michael T.

doi:10.5194/acp-12-11355-2012

Cited by 14 publications

(10 citation statements)

References 46 publications

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“…It seems likely that the decrease in mid-level relative vorticity in this interval weakened the protective pouch at middle levels and allowed dry air intrusion. The dry air sealed the fate of Gaston, as described by Davis and Ahijevych (2012), Smith and Montgomery (2012), and Rutherford and Montgomery (2012). In summary, this entire sequence of events appeared to follow from the weak, bottom-heavy mass flux S. Gjorgjievska and D. J. Raymond: Dynamics and thermodynamics during tropical cyclogenesis 3077 Fig.…”

Section: What Caused Gaston To Decay?mentioning

confidence: 97%

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Interaction between dynamics and thermodynamics during tropical cyclogenesis

Gjorgjievska

Raymond

2014

Atmos. Chem. Phys.

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Abstract. Observational data of tropical disturbances are analyzed in order to investigate tropical cyclogenesis. Data from 37 cases observed during three field campaigns are used to investigate possible correlations between various dynamic and thermodynamic variables. The results show that a strong mid-level vortex is necessary to promote spin up of the lowlevel vortex in a tropical cyclone. This paper presents a theory on the mechanism of this process. The mid-level vortex creates a thermodynamic environment conducive to convection with a more bottom-heavy mass flux profile that exhibits a strong positive vertical gradient in a shallow layer near the surface. Mass continuity then implies that the strongest horizontal mass and vorticity convergence occurs near the surface. This results in low-level vortex intensification.For two of the disturbances that were observed during several consecutive days, evolution of the dynamics and thermodynamics is documented. One of these disturbances, Karl, was observed in the period before it intensified into a tropical storm; the other one, Gaston, was observed after it unexpectedly decayed from a tropical storm to a tropical disturbance. A hypothesis on its decay is presented.

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Section: What Caused Gaston To Decay?mentioning

confidence: 97%

“…5 shows the 5 and 7 km levels). Nor did the Lagrangian analysis of Rutherford and Montgomery (2012) show dry air intrusion between the first two Gaston missions. It appears that the closed circulation of Gaston 1 at both low and middle levels prevented dry air intrusion into the core at this point .…”

Section: What Caused Gaston To Decay?mentioning

confidence: 99%

Interaction between dynamics and thermodynamics during tropical cyclogenesis

Gjorgjievska

Raymond

2014

Atmos. Chem. Phys.

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“…Lagrangian manifolds indicate that the southern boundary of the Kelvin cat's-eye circulation is in fact open, an idea originally suggested in Dunkerton et al (2009). While the opening of a wave pouch can be detrimental to cyclogenesis if dry air enters into the opening (Rutherford and Montgomery 2012;Riemer and Montgomery 2011), in the case of Hurricane Sandy the opening appears to contribute to genesis because of its fortuitous juxtaposition with a favorable thermodynamic environment and seedling vorticity anomalies. Upon entering the eastern Caribbean basin, the wave pouch was presented with several opportunities to grow via accretion with various strands of cyclonic vorticity from the SACZ, a weak EW to the west, and the island of Hispaniola.…”

Section: Discussionmentioning

confidence: 99%

“…A trajectory analysis through the construction of tracer fields provides further detail about transport into the pouch. As is normally the case, the tracer gradients align with the true Lagrangian boundaries in the flow and much of the horizontal transport across the pouch boundaries can be described by regions of accumulation of high or low tracer values (Rutherford and Montgomery 2012). A ''latitude tracer'' field at the 850-hPa surface (latitude advected forward for 48 h and assuming no sources or sinks) can be seen in Fig.…”

Section: The Role Of Vorticity Accretion In the Tropical Cyclogenesismentioning

confidence: 94%

“…The cat's-eye within the wave critical layer is thus dubbed the ''wave's pouch.'' Previous work using observations (Montgomery et al 2010aRutherford and Montgomery 2012) and numerical simulations Wang et al 2010a,b) have documented the applicability of the marsupial paradigm to the tropical cyclogenesis problem on both the synoptic and mesoscales for EW cases. In this paper, we will test the applicability of the marsupial paradigm using satellite and numerical model analyses for the case of Hurricane Sandy.…”

Section: Introductionmentioning

confidence: 99%

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Examining the Roles of the Easterly Wave Critical Layer and Vorticity Accretion During the Tropical Cyclogenesis of Hurricane Sandy

Lussier¹,

L.²,

Blake³

et al. 2014

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The tropical cyclogenesis sequence of Hurricane Sandy is examined. It is shown that genesis occurs within a recirculating Kelvin cat's-eye flow of a westward-propagating tropical wave. The cat's-eye flow is able to provide a protective environment for the mesoscale vortex to grow and is characterized by gradual column moistening and increased areal coverage of deep cumulus convection. These findings are generally consistent with a recently proposed tropical cyclogenesis sequence referred to as the ''marsupial paradigm.'' Sandy's cyclogenesis provides a useful illustration of the marsupial paradigm within a partially open recirculating region, with the opening located south of the pouch center. It is suggested that the opening acts to enhance the genesis process because it is adjacent to an environment characterized by warm, moist air, conditions favorable for tropical cyclogenesis. From a dynamical perspective, accretion of low-level cyclonic vorticity filaments into the developing vortex from several sources (the South American convergence zone, an easterly wave located west of the pre-Sandy wave, and cyclonic vorticity generated along Hispaniola) is documented. Organization and growth of the nascent storm is enhanced by this accretion of cyclonic vorticity. A Lagrangian trajectory analysis is used to assess potential contributions to Sandy's spinup from a Caribbean gyre and the easterly wave that formed Hurricane Tony. This analysis indicates that these features are outside of the Lagrangian flow boundaries that define the pre-Sandy wave and do not directly contribute to spinup of the vortex. Finally, the effectiveness of forecasts from the U.S. and European operational numerical weather prediction models is discussed for this case.

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Dynamical properties of developing tropical cyclones using Lagrangian flow topology

Rutherford

Boothe

Dunkerton

et al. 2018

Quart J Royal Meteoro Soc

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The goal of this study is to characterize the dynamics and structure of tropical cyclone formation from global model analyses to determine thresholds marking the various stages of development which can be computed from the analysis data. We introduce here a new methodology for identifying disturbances that show high likelihood of becoming a tropical depression or tropical storm. We use Lagrangian frame‐independent quantities to define intrinsic coordinates for candidate disturbances prior to and post tropical depression declaration in the best‐track data (HURDAT2). We use these Lagrangian quantities also as metrics for quantifying the strength of these systems within global model analyses as they are declared depressions, storms or hurricanes in HURDAT2. The criteria proposed are more precise than similar Eulerian criteria since the minimum thresholds for development in the best‐track dataset are very close to the threshold at which no false alarms are produced in the global model analyses. Since only very loose thermodynamic thresholds are required, these criteria can be considered dynamically based and require no statistical analysis to compensate for uncertainties in moisture or convection. We describe further the structure of the developing systems using a set of objective profiles where level contours of the Lagrangian averaged rotation rate are mapped to an equivalent radius. Composites of these profiles reveal that the transition to tropical storm strength vortices is marked by the existence of a notable shear sheath outside a region of enhanced solid‐body rotation.

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A Lagrangian analysis of a developing and non-developing disturbance observed during the PREDICT experiment

Cited by 14 publications

References 46 publications

Interaction between dynamics and thermodynamics during tropical cyclogenesis

Interaction between dynamics and thermodynamics during tropical cyclogenesis

Examining the Roles of the Easterly Wave Critical Layer and Vorticity Accretion During the Tropical Cyclogenesis of Hurricane Sandy

Dynamical properties of developing tropical cyclones using Lagrangian flow topology

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