Tropical Cyclone Kinematic Structure Retrieved from Single-Doppler Radar Observations. Part III: Evolution and Structures of Typhoon Alex (1987)

Lee, Wen-Chau; Jou, Ben Jong‐Dao; Chang, Pao‐Liang; Marks, Frank D.

doi:10.1175/1520-0493(2000)129<3982:tcksrf>2.0.co;2

Cited by 43 publications

(33 citation statements)

References 25 publications

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“…GBVTD has been successfully applied to several landfalling TC cases (Lee et al, 2000;Harasti et al, 2004;Lee and Bell, 2007; for potential monitoring and warning applications. It has been shown that GBVTD is capable of retrieving horizontal winds of mature TCs with an accuracy of about 2 m s −1 (Harasti et al, 2004).…”

Section: Introductionmentioning

confidence: 99%

Assimilation of GBVTD‐retrieved winds from single‐Doppler radar for short‐term forecasting of super typhoon Saomai (0608) at landfall

Zhao

Xue

Lee

2011

Quart J Royal Meteoro Soc

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Display technique (GBVTD) has been developed in recent years to retrieve horizontal circulations of tropical cyclones. The technique is able to retrieve axisymmetric tangential and radial winds, asymmetric tangential winds for wave numbers 1-3, and along-beam mean winds in tropical cyclones. It has been successfully applied to tropical cyclone monitoring and warning. This study explores, for the first time, the assimilation of GBVTD-retrieved winds into a tropical cyclone prediction model, and examines its impact relative to that of directly assimilated radial velocity data. super typhoon Saomai (2006), the most intense landfalling typhoon ever recorded in China, is chosen as the test case, and data from the coastal operational radar at Wenzhou, China, are used. The ARPS 3DVAR system is used to assimilate either the radial velocity data directly or the GBVTD-retrieved winds, at 30 min intervals for 2 hours.The assimilation of the GBVTD-retrieved winds results in much improved structure and intensity analyses of Saomai compared to those in the Japan Meteorological Agency mesoscale reanalysis and compared to the analysis assimilating radial velocity (V r ) data directly. The ability of the GBVTD method in providing wind information covering the full circle of the inner-core circulation is the primary reason for its superior performance over direct assimilation of V r data; for the latter, the azimuthal data coverage is often incomplete. With the improved initial conditions, the subsequent forecasts of typhoon intensity, track and precipitation are also improved. The improvements to both track and intensity predictions persist over a 12-hour forecast period, which is mostly after landfall. Subjective and quantitative evaluations of the precipitation and circulation patterns show consistent results. A further sensitivity experiment shows that the axisymmetric wind component in the GBVTD retrieval has the dominant impact on the prediction.

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Section: Introductionmentioning

confidence: 99%

Assimilation of GBVTD‐retrieved winds from single‐Doppler radar for short‐term forecasting of super typhoon Saomai (0608) at landfall

Zhao

Xue

Lee

2011

Quart J Royal Meteoro Soc

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“…Powell et al (1996) assumed that the RMW in Hurricane Andrew (1992) was an M surface, used Jorgensen's equation to estimate the surface RMW from the flight-level RMW, and in turn used this to estimate the surface winds at landfall. In a Doppler winds study, Lee et al (2000) assumed that the RMW of Typhoon Alex (1987) was an M surface and cited Jorgensen in claiming that the slope of that M surface was a function of both intensity and the RMW, thereby supporting all 3 CWs. Additionally, as noted by Kepert (2006), the RMW slopes outward with height in the boundary layer for entirely different reasons than those that cause its outward slope in the free atmosphere.…”

Section: Introductionmentioning

confidence: 99%

Reexamining the Vertical Structure of Tangential Winds in Tropical Cyclones: Observations and Theory

Stern

Nolan

2009

Journal of the Atmospheric Sciences

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A few commonly held beliefs regarding the vertical structure of tropical cyclones drawn from prior studies, both observational and theoretical, are examined in this study. One of these beliefs is that the outward slope of the radius of maximum winds (RMW) is a function of the size of the RMW. Another belief is that the outward slope of the RMW is also a function of the intensity of the storm. Specifically, Shea and Gray found that the RMW becomes increasingly vertical with increasing intensity and decreasing radius. The third belief evaluated here is that the RMW is a surface of constant absolute angular momentum M. These three conventional wisdoms of vertical structure are revisited with a dataset of three-dimensional Doppler wind analyses, comprising seven hurricanes on 17 different days. Azimuthal mean tangential winds are calculated for each storm, and the slopes of the RMW and M surfaces are objectively determined. The outward slope of the RMW is shown to increase with radius, which supports prior studies. In contrast to prior results, no relationship is found between the slope of the RMW and intensity. It is shown that the RMW is indeed closely approximated by an M surface for the majority of storms. However, there is a small but systematic tendency for M to decrease upward along the RMW. Utilizing Emanuel's analytical hurricane model, a new equation is derived for the slope of the RMW in radius-pressure space. This predicts a linear increase of slope with radius and essentially no dependence of slope on intensity. An exactly analogous equation can be derived in log-pressure height coordinates, and a numerical solution yields the same conclusions in geometric height coordinates. These conclusions are further supported by the results of simulations utilizing Emanuel's simple, timedependent, axisymmetric hurricane model. As both the model and the analytical theory are governed by the dual constraints of thermal wind balance and slantwise moist neutrality, it is demonstrated that it is these two assumptions that require the slope of the RMW to be a function of its size but not of the intensity of the storm. Finally, it is shown that within the context of Emanuel's theory, the RMW must very closely approximate an M surface through most of the depth of the vortex.Corresponding author address: Daniel P. Stern, RSMAS/MPO, 1 Although he then confuses his own terminology in the following sentence, writing that ''Shea and Gray also showed that the slope of the radius of maximum winds decrease for stronger storms''; by his convention, the slope actually increases for stronger storms.

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“…These two rainbands formed a 92 nearly closed eyewall at 0600 UTC. The two "moat" regions can be delineated and the eyewalls 93 where the axisymmetric kinematic structure, vorticity, and pressure deficit can be deduced from 102 the GBVTD methodology (Lee et al 1999;2000). The domain of the GBVTD analyses extends 103 from the center of Usagi to 90 km radius and from 1 km to 12 km in the vertical with 1 km grid 104 spacing in both the radial and vertical direction, consistent with the radar sampling resolution.…”

Section: Abstract 23mentioning

confidence: 78%

Doppler Radar Analysis of Triple Eyewalls in Typhoon Usagi (2013)

Zhao

Lin

Lee

et al. 2016

Bulletin of the American Meteorological Society

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23Strong tropical cyclones often undergo eyewall replacement cycles that is accompanied 24 with concentric eyewalls and/or rapid intensity changes while the secondary eyewall contracts 25 radially inward and eventually replaces the inner eyewall. To the best of our knowledge, the only 26 documented partial/incomplete tertiary eyewall has been mostly inferred from two-dimensional 27 satellite images or one-dimensional aircraft flight-level measurements that can be regarded as 28indirect and tangential. This study presents the first high spatial and temporal resolution Doppler 29 radar observations of a tertiary eyewall formation event in Typhoon Usagi (2013) over a 14-hour 30 time period before it makes landfall. The primary (tangential) and secondary (radial) circulations 31 of Usagi deduced from the Ground-Based Velocity Track Display (GBVTD) methodology 32 clearly portrayed three distinct axisymmetric maxima of radar reflectivity, tangential wind, 33 vertical velocity, and vertical vorticity. Usagi's central pressure steadily deepened during the 34 contraction of the secondary and tertiary eyewalls until the tertiary eyewall hit the coast of 35 southeast China that terminated the intensification of Usagi. 36 37

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Tropical Cyclone Kinematic Structure Retrieved from Single-Doppler Radar Observations. Part III: Evolution and Structures of Typhoon Alex (1987)

Cited by 43 publications

References 25 publications

Assimilation of GBVTD‐retrieved winds from single‐Doppler radar for short‐term forecasting of super typhoon Saomai (0608) at landfall

Assimilation of GBVTD‐retrieved winds from single‐Doppler radar for short‐term forecasting of super typhoon Saomai (0608) at landfall

Reexamining the Vertical Structure of Tangential Winds in Tropical Cyclones: Observations and Theory

Doppler Radar Analysis of Triple Eyewalls in Typhoon Usagi (2013)

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