An Ensemble Approach to Investigate Tropical Cyclone Intensification in Sheared Environments. Part II: Ophelia (2011)

Ríos-Berríos, Rosimar; Torn, Ryan D.; Davis, Christopher A.

doi:10.1175/jas-d-15-0245.1

Cited by 29 publications

(22 citation statements)

References 40 publications

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“…Earlier studies have used the criteria of 200-hPa EFC . 10 m s 21 day 21 from 300-to 600-km radius to indicate TC-trough interaction (DeMaria et al 1993;Hanley et al 2001;Rios-Berrios et al 2016). In this simulation, this criterion is met in the 300-100-hPa layer (or the 200-hPa level, not shown) at 120 h. In theory, if EFC is directly affecting the outflow, a maximum in y r should appear around this time frame at larger radii and propagate radially inward with time.…”

Section: Eddy Fluxesmentioning

confidence: 84%

“…A number of studies have examined the interaction of a TC and a trough for real cases using reanalyses, model analyses, or real-data simulations (e.g., Riehl 1954;Sadler 1976Sadler , 1978Holland and Merrill 1984;Vollaro 1989, 1990;Hanley et al 2001;Yu and Kwon 2005;Barrett et al 2016;Rios-Berrios et al 2016). Comparatively few studies exist in the literature that examine TC-trough interaction in a more fundamental manner such as in a modeling framework (Shi et al 1990;Kimball and Evans 2002;Ge et al 2008;Rappin et al 2011).…”

Section: Introductionmentioning

confidence: 99%

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On the Dynamics of Tropical Cyclone and Trough Interactions

Komaromi

Doyle

2018

Journal of the Atmospheric Sciences

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The interaction between a tropical cyclone (TC) and an upper-level trough is simulated in an idealized framework using Coupled Ocean–Atmosphere Mesoscale Prediction System (COAMPS) for Tropical Cyclones (COAMPS-TC) on a β plane. We explore the effect of the trough on the environment, structure, and intensity of the TC. In a simulation that does not have a trough, environmental inertial stability is dominated by Coriolis, and outflow remains preferentially directed equatorward throughout the simulation. In the presence of a trough, negative storm-relative tangential wind in the base of the trough reduces the inertial stability such that the outflow shifts from equatorward to poleward. This interaction results in a ~24-h period of enhanced upper-level divergence coincident with intensification of the TC. Sensitivity tests reveal that if the TC is too far from the trough, favorable interaction does not occur. If the TC is too close to the trough, the storm weakens because of enhanced vertical wind shear. Only when the relative distance between the TC and the trough is 0.2–0.3 times the wavelength of the trough in x and 0.8–1.2 times the amplitude of the trough in y does favorable interaction and TC intensification occur. However, stochastic effects make it difficult to isolate the intensity change associated directly with the trough interaction. Outflow is found to be predominantly ageostrophic at small radii and deflects to the right (in the Northern Hemisphere) since it is unbalanced. The outflow becomes predominantly geostrophic at larger radii but not before a rightward deflection has already occurred. This finding sheds light on why the outflow accelerates toward but generally never reaches the region of lowest inertial stability.

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Section: Eddy Fluxesmentioning

confidence: 84%

Section: Introductionmentioning

confidence: 99%

On the Dynamics of Tropical Cyclone and Trough Interactions

Komaromi

Doyle

2018

Journal of the Atmospheric Sciences

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“…Despite these limitations, our simulations confirm several studies that document compromised TC predictability in environments with moderate vertical wind shear (Bhatia & Nolan, ; Rios‐Berrios et al, ). We have further demonstrated that the predictability of TC intensity and the low‐wave‐number precipitation structure depends on the vertical distribution of moderate shear.…”

Section: Summary and Discussionmentioning

confidence: 99%

“…Such shear magnitudes are near the threshold values that are commonly used to differentiate favorable from unfavorable flow environments (e.g., Gallina & Velden, ; Paterson et al, ). Not surprisingly, the limited predictability of numerous TC cases has been at least partially attributed to the presence of vertical wind shear within this moderate range (Munsell et al, ; Rios‐Berrios et al, ).…”

Section: Introductionmentioning

confidence: 99%

The Predictability of Idealized Tropical Cyclones in Environments With Time‐Varying Vertical Wind Shear

Finocchio

Majumdar

2017

J Adv Model Earth Syst

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This study describes ensembles of idealized tropical cyclone (TC) simulations conducted within a new modeling framework that allows for time‐varying environments. These simulations are used to examine the predictability implications of exposing a TC to environmental wind profiles with different structures and magnitudes of vertical wind shear. In moderate shear magnitudes, the TCs exposed to more deeply distributed shear are weaker and exhibit a more uncertain intensity evolution than TCs exposed to shallow‐upper level shear. The weaker mean intensity and higher uncertainty are found to be associated with a bifurcation in the vortex tilt response. Structural predictability time scales, computed as the time it takes for errors in the amplitude and phase of azimuthal asymmetries of radar reflectivity to saturate, are generally between 2 and 3 days for low‐wave‐number asymmetries. These asymmetries are slightly more predictable in deeply distributed shear and in the rainband region due to the larger vortex tilt magnitudes of many ensemble members providing more robust forcing for a quasi‐stationary rainband feature. Once the magnitude of vertical wind shear increases to universally destructive levels at the end of the simulations, intensity errors begin to decrease and low‐wave‐number structural errors desaturate as the quasi‐stationary rainband becomes a consistent feature in members of both ensembles. The most significant error desaturation occurs in TCs previously exposed to shallow‐upper level shear. These results suggest that the intensity and precipitation structure are more difficult to forecast when a TC is exposed to moderate and deeply distributed vertical wind shear.

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“…A major impediment of accurate tropical cyclone (TC) forecasts is the interaction of TCs with environmental vertical wind shear (VWS). Although VWS is one of the most inhibiting factors of TC intensification (Merrill 1988;DeMaria and Kaplan 1994;Paterson et al 2005;Hendricks et al 2010), TCs can intensify under VWS magnitudes that are neither too weak nor too strong (moderate shear hereafter; Molinari et al 2004Molinari et al , 2006Molinari and Vollaro 2010;Montgomery et al 2010;Foerster et al 2014;Stevenson et al 2014;Rios-Berrios et al 2016b,a;Zawislak et al 2016;Rios-Berrios and Torn 2017;Nguyen et al 2017). Consequently, intensity changes are more difficult to predict for moderate VWS scenarios than for weak or strong VWS (Bhatia and Nolan 2013;Finocchio and Majumdar 2017).…”

Section: Introductionmentioning

confidence: 99%

A Hypothesis for the Intensification of Tropical Cyclones under Moderate Vertical Wind Shear

Ríos-Berríos

Davis

Torn

2018

Journal of the Atmospheric Sciences

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A major open issue in tropical meteorology is how and why some tropical cyclones intensify under moderate vertical wind shear. This study tackles that issue by diagnosing physical processes of tropical cyclone intensification in a moderately sheared environment using a 20-member ensemble of idealized simulations. Consistent with previous studies, the ensemble shows that the onset of intensification largely depends on the timing of vortex tilt reduction and symmetrization of precipitation. A new contribution of this work is a process-based analysis following a shear-induced midtropospheric vortex with its associated precipitation. This analysis shows that tilt reduction and symmetrization precede intensification because those processes are associated with a substantial increase in near-surface vertical mass fluxes and equivalent potential temperature. A vorticity budget demonstrates that the increased near-surface vertical mass fluxes aid intensification via near-surface stretching of absolute vorticity and free-tropospheric tilting of horizontal vorticity. Importantly, tilt reduction happens because of a vortex merger process—not because of advective vortex alignment—that yields a single closed circulation over a deep layer. Vortex merger only happens after the midtropospheric vortex reaches upshear left, where the flow configuration favors near-surface vortex stretching, deep updrafts, and a substantial reduction of low-entropy fluxes. These results lead to the hypothesis that intensification under moderate shear happens if and when a “restructuring” process is completed, after which a closed circulation favors persistent vorticity spinup and recirculating warm, moist air parcels.

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An Ensemble Approach to Investigate Tropical Cyclone Intensification in Sheared Environments. Part II: Ophelia (2011)

Cited by 29 publications

References 40 publications

On the Dynamics of Tropical Cyclone and Trough Interactions

On the Dynamics of Tropical Cyclone and Trough Interactions

The Predictability of Idealized Tropical Cyclones in Environments With Time‐Varying Vertical Wind Shear

A Hypothesis for the Intensification of Tropical Cyclones under Moderate Vertical Wind Shear

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