A 15-Year Climatology of North Atlantic Tropical Cyclones. Part I: Size Parameters

Kimball, Sytske K.; Mulekar, Madhuri S.

doi:10.1175/1520-0442(2004)017<3555:aycona>2.0.co;2

Cited by 197 publications

(202 citation statements)

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“…Storm geolocation based on geostationary imagery is accurate to within the nominal 4 km pixel resolution at the sub-satellite point, superior to any of the other products used in our analysis. August and September were chosen because they represent the peak of the Atlantic hurricane season (Kimball and Mulekar, 2004).…”

Section: A1 Datasets and Filtersmentioning

confidence: 99%

Tropical cyclogenesis in a tropical wave critical layer: easterly waves

2009

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Abstract. The development of tropical depressions within tropical waves over the Atlantic and eastern Pacific is usually preceded by a "surface low along the wave" as if to suggest a hybrid wave-vortex structure in which flow streamlines not only undulate with the waves, but form a closed circulation in the lower troposphere surrounding the low. This structure, equatorward of the easterly jet axis, is identified herein as the familiar critical layer of waves in shear flow, a flow configuration which arguably provides the simplest conceptual framework for tropical cyclogenesis resulting from tropical waves, their interaction with the mean flow, and with diabatic processes associated with deep moist convection. The recirculating Kelvin cat's eye within the critical layer represents a sweet spot for tropical cyclogenesis in which a proto-vortex may form and grow within its parent wave. A common location for storm development is given by the intersection of the wave's critical latitude and trough axis at the center of the cat's eye, with analyzed vorticity centroid nearby. The wave and vortex live together for a time, and initially propagate at approximately the same speed. In most cases this coupled propagation continues for a few days after a tropical depression is identified. For easterly waves, as the name suggests, the propagation is westward. It is shown that in order to visualize optimally the associated Lagrangian motions, one should view the flow streamlines, or stream function, in a frame of reference translating horizontally with the phase propagation of the parent wave. In this co-moving frame, streamlines are approximately equivalent to particle trajectories. The closed circulation is quasi-stationary, and a dividing streamline separates air within the cat's eye from air outside. The critical layer equatorward of the easterly jet axis is important to tropical cyclogenesis because its cat's eye provides (i) a region of cyclonic vorticity and weak deformation by Correspondence to: T. J. Dunkerton (tim@nwra.com) the resolved flow, (ii) containment of moisture entrained by the developing gyre and/or lofted by deep convection therein, (iii) confinement of mesoscale vortex aggregation, (iv) a predominantly convective type of heating profile, and (v) maintenance or enhancement of the parent wave until the vortex becomes a self-sustaining entity and emerges from the wave as a tropical depression. The entire sequence is likened to the development of a marsupial infant in its mother's pouch. These ideas are formulated in three new hypotheses describing the flow kinematics and dynamics, moist thermodynamics and wave/vortex interactions comprising the "marsupial paradigm". A survey of 55 named tropical storms in 1998-2001 reveals that actual critical layers sometimes resemble the ideal east-west train of cat's eyes, but are usually less regular, with one or more recirculation regions in the co-moving frame. It is shown that the kinematics of isolated protovortices carried by the wave also can be visualized in a fra...

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Section: A1 Datasets and Filtersmentioning

confidence: 99%

Tropical cyclogenesis in a tropical wave critical layer: easterly waves

2009

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“…Merrill (1984) showed that the mean radius of the outermost closed isobar of Atlantic hurricanes tended to be smaller than their western North Pacific (WNP) counterparts (being 3.0° vs. 4.4° latitude). The average radius of maximum wind (R m ) in Atlantic and eastern Pacific hurricanes is roughly 45 -55 km, with a reasonable range of 10 -110 km (Shea and Gray 1973;Hsu and Yan 1998;Kimball and Mulekar 2004;Willoughby and Rahn 2004;Mallen et al 2005;Vickery and Wadhera 2008). Data are more limited for WNP typhoons as routine reconnaissance flights there were terminated after September 1987, although Weatherford and Gray (1988a, b) reported that the mean WNP TC eye inner radar radius (IRR) for these storms is around 20 km, with a large variation spanning 4 -111 km.…”

Section: Introductionmentioning

confidence: 99%

Tropical Cyclone Track and Structure Sensitivity to Initialization in Idealized Simulations: A Preliminary Study

Yang¹,

Fovell²,

Corbosiero³

2011

Terr. Atmos. Ocean. Sci.

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In the absence of environmental steering, tropical cyclone (TC) motion largely reflects "beta drift" owing to differential planetary vorticity advection by the storm's outer circulation. It is known that model physics choices (especially those relating to convection) can significantly alter these outer winds and thus the storm track. Here, semi-idealized simulations are used to explore the influence of the initialization on subsequent vortex evolution and motion. Specifically, TCs bred from a buoyant "bubble" are compared to bogussed vortices having a wide variety of parameterized shapes and sizes matching observations.As expected, the bogussed storms commencing with the strongest outer winds propagated fastest and, as a result, huge structure-dependent position differences quickly appeared. However, the forward speed variation among the initially bogussed TCs subsequently declined as a progressive homogenization harmonized the initially supplied structural differences. The homogenization likely involved model physics such as microphysics. This result casts doubt on the ability of models to retain and propagate forward information supplied at the initialization by advanced data assimilation techniques or parameterized vortex wind profiles.Asymmetries in near-core convective heating emerged as an important structural aspect that survived the homogenization tendency. The bubble and bogussed TCs developed markedly different heating patterns, which appear to help explain why the artificially-established storms tended to move about three times faster than their bubble counterparts. The reasons for this are not presently understood fully.

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“…The two broken lines indicate the range in which 95 % of the plots fall (i.e., 95 % prediction interval). The Atlantic TC plot is derived from Kimball et al (2004). (Knaff, 2010), among other information (Fig.…”

Section: New R Max Estimation Based On the 50 Kt Wind Radiusmentioning

confidence: 99%

“…Therefore, to minimize the risk of over-or underestimation of storm surges, the surge simulations should be repeated for different estimation lines covering a certain percentage of the data (e.g., a 95 % prediction interval) such as R max = 0.15 R 50 − 0.35 R 50 . Figure 6 also indicates the estimated R max for the Atlantic from Kimball et al (2004), after converting the wind speed from a 1 to a 10 min mean and an interpolation to match the R 50 .…”

Section: New R Max Estimation Based On the 50 Kt Wind Radiusmentioning

confidence: 99%

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Maximum wind radius estimated by the 50 kt radius: improvement of storm surge forecasting over the western North Pacific

Takagi

2016

Nat. Hazards Earth Syst. Sci.

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Abstract. Even though the maximum wind radius (R max )is an important parameter in determining the intensity and size of tropical cyclones, it has been overlooked in previous storm surge studies. This study reviews the existing estimation methods for R max based on central pressure or maximum wind speed. These over-or underestimate R max because of substantial variations in the data, although an average radius can be estimated with moderate accuracy. As an alternative, we propose an R max estimation method based on the radius of the 50 kt wind (R 50 ). Data obtained by a meteorological station network in the Japanese archipelago during the passage of strong typhoons, together with the JMA typhoon best track data for 1990-2013, enabled us to derive the following simple equation, R max = 0.23 R 50 . Application to a recent strong typhoon, the 2015 Typhoon Goni, confirms that the equation provides a good estimation of R max , particularly when the central pressure became considerably low. Although this new method substantially improves the estimation of R max compared to the existing models, estimation errors are unavoidable because of fundamental uncertainties regarding the typhoon's structure or insufficient number of available typhoon data. In fact, a numerical simulation for the 2013 Typhoon Haiyan as well as 2015 Typhoon Goni demonstrates a substantial difference in the storm surge height for different R max . Therefore, the variability of R max should be taken into account in storm surge simulations (e.g., R max = 0.15 R 50 -0.35 R 50 ), independently of the model used, to minimize the risk of over-or underestimating storm surges. The proposed method is expected to increase the predictability of major storm surges and to contribute to disaster risk management, particularly in the western North Pacific, including countries such as Japan, China, Taiwan, the Philippines, and Vietnam.

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A 15-Year Climatology of North Atlantic Tropical Cyclones. Part I: Size Parameters

Cited by 197 publications

References 18 publications

Tropical cyclogenesis in a tropical wave critical layer: easterly waves

Tropical cyclogenesis in a tropical wave critical layer: easterly waves

Tropical Cyclone Track and Structure Sensitivity to Initialization in Idealized Simulations: A Preliminary Study

Maximum wind radius estimated by the 50 kt radius: improvement of storm surge forecasting over the western North Pacific

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A 15-Year Climatology of North Atlantic Tropical Cyclones. Part I: Size Parameters

Cited by 197 publications

References 18 publications

Tropical cyclogenesis in a tropical wave critical layer: easterly waves

Tropical cyclogenesis in a tropical wave critical layer: easterly waves

Tropical Cyclone Track and Structure Sensitivity to Initialization in Idealized Simulations: A Preliminary Study

Maximum wind radius estimated by the 50 kt radius: improvement of storm surge forecasting over the western North Pacific

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Product

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Maximum wind radius estimated by the 50 kt radius: improvement of storm surge forecasting over the western North Pacific