The Dependence of Tropical Cyclone Pressure Tendency on Size

Sparks, Nathan; Toumi, Ralf

doi:10.1029/2022gl098926

Cited by 5 publications

(5 citation statements)

References 42 publications

(68 reference statements)

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“…Sparks and Toumi (2022a) showed how surface pressure increases are driven by the net inflow into the column for a weakening storm. The pressure tendency depends on both the inflow and the size of the cyclone (Sparks & Toumi, 2022b). Their framework does not invoke inertial stability and is consistent with the observations here.…”

Section: Discussionmentioning

confidence: 99%

Boundary layer profile of decaying and non‐decaying tropical storms near landfall

Tsui,

Chan,

Toumi

2023

Atmospheric Science Letters

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The vertical profile of the wind structure of translating tropical cyclones, including the associated azimuthal asymmetry, has been the subject of existing theoretical and observational studies using dropsondes. Most of these studies are based on data collected from relatively strong cyclones over the Atlantic. Here we explore the tropical cyclone boundary layer wind profile of mainly relatively weak landfalling cyclones near Hong Kong. We find that decaying tropical storms have a much larger mid‐ to low‐level inflow angle than those that are intensifying or in steady‐state. The inflow angles of intensifying, steady‐state and decaying tropical storms converge towards the top of the boundary layer. The wind speed reduces through the boundary layer in a similar way in all three cases. The combination of these factors means that decaying tropical storms have stronger inflow than intensifying and steady‐state ones. We attribute these local effects to remote enhanced surface friction over land when the storms are weakening.

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Section: Discussionmentioning

confidence: 99%

Boundary layer profile of decaying and non‐decaying tropical storms near landfall

Tsui,

Chan,

Toumi

2023

Atmospheric Science Letters

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“…To do so, we treated RI as an extreme‐detecting problem and cluster the initial V max and RMW, with a subsequent ΔV 24 for all global TCs from 2004 to 2020. These variables were selected because they define the initial state of the vortex before RI, as demonstrated by previous theoretical and observational studies (e.g., Carrasco et al., 2014; Li et al., 2021; Mallen et al., 2005; Y. Wang et al., 2021; Sparks & Toumi, 2022) and our sensitivity experiments. Over 12,000 events extracted from the IBTrACS best‐track data were clustered using the K‐Means clustering algorithm; one cluster with a minimum ΔV 24 of 45 kt/24hr (23.2 m/s/24hr) was thereby distinctly separated from the others.…”

Section: Discussionmentioning

confidence: 99%

“…In addition, the vortex size reflects feedback between the primary circulation and inner‐core processes (Mallen et al., 2005; Sparks & Toumi, 2022), and affects the subsequent intensification (Emanuel, 1989). Studies based on best‐track data have confirmed that RI events rarely occur when RMW is larger than 100 km because a small RMW favors intensification due to the conservation of angular momentum (Carrasco et al., 2014; Xu & Wang, 2018).…”

Section: Introductionmentioning

confidence: 99%

Revisiting the Definition of Rapid Intensification of Tropical Cyclones by Clustering the Initial Intensity and Inner‐Core Size

Tang

Toumi

et al. 2022

JGR Atmospheres

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Rapid intensification (RI) of tropical cyclones (TCs) provides a great challenge in operational forecasting and contributes significantly to the development of major TCs. RI is commonly defined as an increase in the maximum sustained surface wind speed of at least a certain threshold within 24 hr. The most widely used threshold is 30 kt (15.4 m/s), which was determined statistically. Here we propose a new definition for RI by objectively clustering TCs using the intensification rate, initial intensity, and radius of the maximum wind speed (RMW). A group of 770 samples is separated at a threshold of 45 kt (23.2 m/s). The threshold is 40 kt (20.6 m/s) for the western North Atlantic, where TC size measurements are more reliable. Monte Carlo experiments demonstrate that the proposed threshold is robust even considering the uncertainty in RMW of as high as 30 km. We show that, when a TC undergoes RI, its maximum wind speed is approximately 60 ± 15 kt (30.9 ± 7.7 m/s) and the RMW is 45 ± 20 km. The new threshold outperforms the conventional threshold of 30 kt/24 hr in describing the bimodal distribution of lifetime maximum intensity and explaining the annual count of Category 5 TCs. This new definition provides a more physically based threshold and describes a more reliable representation of extreme events. Although more comparisons are needed for operational application, it is likely to be desirable for case‐based process studies and could provide a more valuable metric for TC intensification classification and research.

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“…A weak dependence of TC size on intensity has been observed 25 , 26 , as has an important increase of size during the decay of a TC which contributes to the footprint of any damage 27 . We represent this behaviour within our model.…”

Section: Methodsmentioning

confidence: 99%

The Imperial College Storm Model (IRIS) Dataset

Sparks,

Toumi

2024

Sci Data

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Assessing tropical cyclone risk on a global scale given the infrequency of landfalling tropical cyclones (TC) and the short period of reliable observations remains a challenge. Synthetic tropical cyclone datasets can help overcome these problems. Here we present a new global dataset created by IRIS, the ImpeRIal college Storm model. IRIS is novel because, unlike other synthetic TC models, it only simulates the decay from the point of lifetime maximum intensity. This minimises the bias in the dataset. It takes input from 42 years of observed tropical cyclones and creates a 10,000 year synthetic dataset of wind speed which is then validated against the observations. IRIS captures important statistical characteristics of the observed data. The return periods of the landfall maximum wind speed are realistic globally.

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The Dependence of Tropical Cyclone Pressure Tendency on Size

Cited by 5 publications

References 42 publications

Boundary layer profile of decaying and non‐decaying tropical storms near landfall

Boundary layer profile of decaying and non‐decaying tropical storms near landfall

Revisiting the Definition of Rapid Intensification of Tropical Cyclones by Clustering the Initial Intensity and Inner‐Core Size

The Imperial College Storm Model (IRIS) Dataset

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