30 results on '"Hurricanes -- Analysis"'
Search Results
2. Convectively generated potential vorticity in rainbands and formation of the secondary eyewall in Hurricane Rita of 2005
- Author
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Judt, Falko and Chen, Shuyi S.
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Hurricane Rita, 2005 -- Analysis ,Meteorological research -- Analysis ,Dynamic meteorology -- Analysis ,Hurricanes -- Analysis ,Earth sciences ,Science and technology - Abstract
Eyewall replacements in mature tropical cyclones usually cause intensity fluctuations. One reason for eyewall replacements remaining a forecasting challenge is the lack of understanding of how secondary eyewalls form. This study uses high-resolution, full-physics-model forecast fields of Hurricanes Katrina and Rita (2005) to better understand potential vorticity (PV) generation in the rainbands and the role that convectively generated PV played in the formation of a secondary eyewall in Hurricane Rita. Previous studies have focused on dynamic processes in the inner core and/or the effects of certain specified PV distributions. However, the initial development of a concentric PV ring in the rainband region has not been fully addressed. Katrina and Rita were extensively observed by three research aircraft during the Hurricane Rainband and Intensity Change Experiment (RAINEX), which was designed to study the interaction of the rainbands and the inner core. Rita developed a secondary eyewall and went through an eyewall replacement cycle, whereas Katrina maintained a single primary eyewall during the RAINEX observation period before landfall. These distinct features observed in RAINEX provide a unique opportunity to examine the physical and dynamical processes that lead to formation of concentric eyewalls. A triply nested high-resolution model with 1.67-km resolution in the innermost domain, initialized with operational model forecasts in real time during RAINEX, is used in this study. Analyses of wind, vorticity, PV, and vortex Rossby wave (VRW) activity in the inner-core region were conducted using both RAINEX airborne observations and model output. The results show that a higher PV generation rate and accumulation in the rainband region in Rita leads to a secondary PV/vorticity maximum, which eventually became the secondary eyewall. A strong moat area developed between the primary eyewall and the concentric ring of convection in Rita, prohibiting VRW activity. In contrast, VRWs propagated radially outward from the inner core to the rainband region in Katrina. The VRWs were not a contributing factor in the initial formation of the secondary eyewall in Rita since the moat region with near-zero PV gradient did not allow for radial propagation of VRWs. The large accumulation of convectively generated PV in the rainband region was the key factor in the formation of the secondary eyewall in Rita. DOI: 10.1175/2010JAS3471.1 more...
- Published
- 2010
Catalog
3. Multiscale observations of Hurricane Dennis (2005): the effects of hot towers on rapid intensification
- Author
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Guimond, Stephen R., Heymsfield, Gerald M., and Turk, F. Joseph
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Meteorological research -- Analysis ,Dynamic meteorology -- Analysis ,Hurricanes -- Analysis ,Radar meteorology -- Analysis ,Earth sciences ,Science and technology - Abstract
A synthesis of remote sensing and in situ observations throughout the life cycle of Hurricane Dennis (2005) during the NASA Tropical Cloud Systems and Processes (TCSP) experiment is presented. Measurements from the ER-2 Doppler radar (EDOP), the Advanced Microwave Sounding Unit (AMSU), airborne radiometer, and flight-level instruments are used to provide a multiscale examination of the storm. The main focus is an episode of deep convective bursts ('hot towers') occurring during a mature stage of the storm and preceding a period of rapid intensification (11-hPa pressure drop in 1 h 35 min). The vigorous hot towers penetrated to 16-km height, had maximum updrafts of 20 m [s.sup.-1] at 12-14-km height, and possessed a strong transverse circulation through the core of the convection. Significant downdrafts (maximum of 10-12 m [s.sup.-1]) on the flanks of the updrafts were observed, with their cumulative effects hypothesized to result in the observed increases in the warm core. In one ER-2 overpass, subsidence was transported toward the eye by 15-20 m [s.sup.-1] inflow occurring over a deep layer (0.5-10 km) coincident with a hot tower. Fourier analysis of the AMSU satellite measurements revealed a large shift in the storm's warm core structure, from asymmetric to axisymmetric, ~12 h after the convective bursts began. In addition, flight-level wind calculations of the axisymmetric tangential velocity and inertial stability showed a contraction of the maximum winds and an increase in the stiffness of the vortex, respectively, after the EDOP observations. The multiscale observations presented here reveal unique, ultra-high-resolution details of hot towers and their coupling to the parent vortex, the balanced dynamics of which can be generally explained by the axisymmetrization and efficiency theories. DOI: 10.1175/2009JAS3119.1 more...
- Published
- 2010
4. Hurricane response of nearshore borrow pits from airborne bathymetric lidar
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Kennedy, Andrew B., Slatton, K. Clint, Starek, Michael, Kampa, Kittipat, and Cho, Hyun-Chong
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Holes -- Environmental aspects ,Hurricanes -- Analysis ,Hurricanes -- Environmental aspects ,Hurricanes -- United States ,Engineering and manufacturing industries ,Science and technology - Abstract
Airborne bathymetric lidar surveys taken in Florida before and after the severe 2004 and 2005 hurricane seasons show infilling of seventeen dredged nearshore borrow pits. During these seasons, groups of pits captured volumes that were the equivalent of up to four years of net longshore transport, even though only one of the seventeen pits studied was inside the presumed depth of closure. Unsurprisingly, dimensionless infilling increased strongly with the ratio of wave height to pit depth. For open coast pits with large alongshore lengths, cross-shore infilling appeared to dominate over longshore infilling but both processes may be of comparable importance in shorter pits. Infilling of three borrow pits adjacent to ebb shoals was found to be considerably larger than on open coasts. Bathymetric changes in borrow pits occurred at greater depths than on nearby undisturbed profiles. Crude estimates of the long term infilling rates from tropical cyclones indicate that annual infilling volumes may be equivalent to more than one quarter of the expected net longshore transport at some locations. However, the episodic nature of hurricanes means that infilling events will be highly irregular. CE Database subject headings: Coastal engineering; Sediment transport; Water waves; Hurricanes; Florida. Author keywords: Coastal engineering; Sediment transport; Water waves; Hurricanes. DOI: 10.1061/(ASCE)WW.1943-5460.0000024 more...
- Published
- 2010
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5. Impact of airborne Doppler radar data assimilation on the numerical simulation of intensity changes of Hurricane Dennis near a landfall
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Pu, Zhaoxia, Li, Xuanli, and Sun, Juanzhen
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Hurricane Dennis, 1999 -- Analysis ,Radar systems -- Analysis ,Hurricanes -- Analysis ,Radar meteorology -- Analysis ,Hurricane forecasting -- Analysis ,Rain and rainfall -- Analysis ,Meteorological research -- Analysis ,Dynamic meteorology -- Analysis ,Numerical weather forecasting -- Analysis ,Earth sciences ,Science and technology - Abstract
Accurate forecasting of a hurricane's intensity changes near its landfall is of great importance in making an effective hurricane warning. This study uses airborne Doppler radar data collected during the NASA Tropical Cloud Systems and Processes (TCSP) field experiment in July 2005 to examine the impact of airborne radar observations on the short-range numerical simulation of hurricane track and intensity changes. A series of numerical experiments is conducted for Hurricane Dennis (2005) to study its intensity changes near a landfall. Both radar reflectivity and radial velocity-derived wind fields are assimilated into the Weather Research and Forecasting (WRF) model with its three-dimensional variational data assimilation (3DVAR) system. Numerical results indicate that the radar data assimilation has greatly improved the simulated structure and intensity changes of Hurricane Dennis. Specifically, the assimilation of radar reflectivity data shows a notable influence on the thermal and hydrometeor structures of the initial vortex and the precipitation structure in the subsequent forecasts, although its impact on the intensity and track forecasts is relatively small. In contrast, assimilation of radar wind data results in moderate improvement in the storm-track forecast and significant improvement in the intensity and precipitation forecasts of Hurricane Dennis. The hurricane landfall, intensification, and weakening during the simulation period are well captured by assimilating both radar reflectivity and wind data. DOI: 10.1175/2009JAS3121.1 more...
- Published
- 2009
6. Numerical simulation of Hurricane Bonnie (1998). Part III: energetics
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Hogsett, Wallace and Zhang, Da-Lin
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Hurricane Bonnie, 1998 -- Analysis ,Meteorological research -- Analysis ,Dynamic meteorology -- Analysis ,Hurricanes -- Analysis ,Earth sciences ,Science and technology - Abstract
Despite considerable research on tropical cyclones (TCs), few studies have been performed to examine inner-core energy conversions because of the lack of high-resolution data. In this study, the TC energetic characteristics in relation to intensity and structural changes under different sheared environments are investigated using a 5-day cloud-resolving simulation of Hurricane Bonnie (1998). Results show that in the presence of intense vertical shear Bonnie undergoes high-frequency fluctuations in intensity and energy conversions (at a time scale of 3 h) during the partial eyewall stage. The fluctuations are closely related to the life cycle of individual convective elements that propagate cyclonically around the downshear portion of the eyewall. The energy conversions are shown to be maximized in the vicinity of the radius of maximum wind (RMW), thus affecting strongly TC intensity. On average, about 2% of latent energy can be converted to kinetic energy to increase TC intensity. After the vertical shear subsides below a threshold, intensity fluctuations become small as convective elements reorganize into an axisymmetric eyewall in which energy conversions are more evenly distributed. Fourier decomposition is conducted to separate the wavenumber-0, -1, and -2 components of inner-core energetics. Whereas wavenumber-1 perturbations dominate the partial eyewall stage, the propagation of wavenumber-2 perturbations is shown to be closely related to individual convective elements during both the partial eyewall and axisymmetric stages. The wavenumber-2 perturbations can be traced as they move around the eyewall in the form of vortex-Rossby waves, and they play a role in determining the large intensity fluctuations during the partial eyewall stage and the formation of an outer eyewall to replace the partial inner eyewall at the later stage. more...
- Published
- 2009
7. Numerical modeling of dynamic wave force acting on Escambia Bay bridge deck during Hurricane Ivan
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Huang, Wenrui and Xiao, Hong
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Hurricane Ivan, 2004 -- Analysis ,Waterfront development -- Analysis ,Waterfront development -- Models ,Storm surges -- Analysis ,Storm surges -- Models ,Hurricanes -- Analysis ,Hurricanes -- Models ,Engineering and manufacturing industries ,Science and technology - Abstract
Bridge decks in Escambia Bay were damaged during the storm surge of Hurricane Ivan in 2004. In this study, a numerical wave-load model based on the incompressible Reynolds averaged Navier--Stokes equations and k-[epsilon] equations has been used to investigate dynamic wave forces exerted on the bridge deck. The volume of fluid method is adopted in the model to describe dynamic free surface, which is capable of simulating complex discontinuous free surface during wave breaking and wave-deck interactions. The model was satisfactorily tested against experimental data of uplift wave forces on horizontal plates. The validated model was applied to investigate wave forces acting on the bridge deck in Escambia Bay in the case of Hurricane Ivan. The time history of wave profiles, turbulent velocity fields, and dynamic uplift and horizontal forces acting on the full-scale bridge deck were simulated and analyzed. Results indicate that, during the storm surge event of Hurricane Ivan, the maximum uplifting wave forces were larger than the weight of the simply supported bridge deck, causing direct damage to the deck. Wave forces on three different deck elevations are discussed. Comparisons of numerical modeling results to maximum wave forces obtained from empirical equations are provided as references for coastal hazard assessment and bridge design. DOI: 10.1061/(ASCE)0733-950X(2009)135:4(164) CE Database subject headings: Storm surges; Bridge decks; Uplifting; Numerical models; Hurricanes: Florida. more...
- Published
- 2009
8. Cloud microphysics impact on hurricane track as revealed in idealized experiments
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Fovell, Robert G., Corbosiero, Kristen L., and Kuo, Hung-chi
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Clouds -- Environmental aspects ,Hurricanes -- United States ,Hurricanes -- Analysis ,Atmospheric physics -- Research ,Earth sciences ,Science and technology - Abstract
Analyses of tropical cyclones created in an idealized environment reveal how and why cloud microphysical assumptions can influence storm motion, including speed and direction. It is well known that in the absence of a mean flow, a leading factor in storm propagation is the establishment of 'beta gyres' owing to planetary vorticity advection by the storm's circulation. Previous research demonstrated that tangential winds well beyond the core influence storm motion by helping to determine the gyres' orientation and intensity. Microphysical assumptions, especially involving average particle fall speeds, can strongly influence the winds at outer radius. More specifically, microphysics modulates the radial distribution of column-average virtual temperature, which largely determines the radial surface pressure gradient and therefore the winds because they tend to be in gradient balance beyond the core. Microphysics schemes can differ markedly with respect to average fall speed, depending on the complexity of the scheme and how interactions among condensation types are handled. Average fall speed controls the outward movement of particles produced in the eyewall into the anvil, where they can influence the environment through cloud-radiative interactions and phase changes. With the assistance of some special sensitivity tests, the influence of microphysics and fall speed on radial temperature gradients, leading to different outer wind strengths and tracks, is shown. Among other things. this work demonstrates that the treatment of outer rainbands in operational models can potentially influence how simulated storms move, thus affecting position forecasts. more...
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- 2009
9. Hydrodynamic investigation of coastal bridge collapse during Hurricane Katrina
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Chen, Qin, Wang, Lixia, and Zhao, Haihong
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Hurricane Katrina, 2005 -- Investigations ,Hurricane Katrina, 2005 -- Analysis ,Hurricanes -- Investigations ,Hurricanes -- Analysis ,Water waves -- Investigations ,Water waves -- Analysis ,Storm surges -- Investigations ,Storm surges -- Analysis ,Bridge failures -- Investigations ,Bridge failures -- Analysis ,Company legal issue ,Engineering and manufacturing industries ,Science and technology - Abstract
A number of U.S. coastal bridges have been destroyed by hurricanes, including three highway bridges in Mississippi and Louisiana during Hurricane Katrina (2005). This paper addresses three fundamental questions on the coastal bridge failures: (1) what were the hydrodynamic conditions near the failed bridge during the hurricane; (2) what was the cause of the bridge collapse; and (3) what was the magnitude of the hydrodynamic loading on the bridge under the extreme hurricane conditions. Guided by field observations of winds, waves, and water levels, two numerical models for storm surges and water waves are coupled to hindcast the hydrodynamic conditions. Fairly good agreement between the modeled and measured high watermarks and offshore wave heights is found, allowing an estimate of the surge and wave conditions near the bridges in nested domains with higher resolutions. The output of the coupled wave-surge models is utilized to determine the static buoyant force and wave forces on the bridge superstructure based on empirical equations derived from small-scale hydraulic tests for elevated decks used in the coastal and offshore industry. It is inferred that the bridge failure was caused by the wind waves accompanied by the storm surge, which raised the water level to an elevation where surface waves generated by strong winds over a relatively short fetch were able to strike the bridge superstructure. The storm waves produced both an uplift force and a horizontal force on the bridge decks. The magnitude of wave uplift force from individual waves exceeded the weight of the simple span bridge decks and the horizontal force overcame the resistance provided by the connections of the bridge decks to the pilings. The methodology for determining the hydrodynamic forcing on bridge decks can be used to produce a preliminary assessment of the vulnerability of existing coastal bridges in hurricane-prone areas. CE Database subject headings: Storm surge; Surface waves; Coupling; Wave forces; Bridge failure; Hurricanes; Mississippi; Louisiana. more...
- Published
- 2009
10. Internal control of hurricane intensity variability: the dual nature of potential vorticity mixing
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Rozoff, Christopher M., Kossin, James P., Schubert, Wayne H., and Mulero, Pedro J.
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Hurricanes -- United States ,Hurricanes -- Analysis ,Vorticity -- Environmental aspects ,Earth sciences ,Science and technology - Abstract
In hurricane eyewalls, the vertical stretching effect tends to produce an annular ring of high vorticity. Idealized, unforced nondivergent barotropic model results have suggested such rings of vorticity are often barotropically unstable, leading to strong asymmetric mixing events where vorticity is mixed inward into a more stable configuration. Such mixing events most often result in weakened maximum winds. The manner in which forcing modifies these unforced simulations remains an open question. In the current study, a forced, two-dimensional barotropic model is used to systematically study the sensitivity of vorticity rings to ring geometry and spatially and temporally varying forcing. The simulations reveal an internal mechanism that interrupts the intensification process resulting from vorficity generation in the hurricane eyewall. This internal control mechanism is due to vorticity mixing in the region of the eye and eyewall and can manifest itself in two antithetical forms--as a transient 'intensification brake' during symmetric intensification or as an enhancer of intensification through efficient transport of vorticity from the eyewall, where it is generated, to the eye. more...
- Published
- 2009
11. Lessons from Hurricane Katrina storm surge on bridges and buildings
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Robertson, Ian N., Riggs, H. Ronald, Yim, Solomon C.S., and Young, Yin Lu
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Hurricane Katrina, 2005 -- Analysis ,Hurricanes -- Analysis ,Engineering and manufacturing industries ,Science and technology - Abstract
The storm surge associated with Hurricane Katrina caused tremendous damage along the Gulf Coast in Louisiana, Mississippi, and Alabama. Similar damage was observed subsequent to the Indian Ocean tsunami of December 26, 2004. In order to gain a better understanding of the performance of engineered structures subjected to coastal inundation due to tsunami or hurricane storm surge, the writers surveyed damage to bridges, buildings, and other coastal infrastructure subsequent to Hurricane Katrina. Numerous lessons were learned from analysis of the observed damage, and these are reported herein. A number of structures experienced significant structural damage due to storm surge and wave action. Structural members submerged during the inundation were subjected to significant hydrostatic uplift forces due to buoyancy, enhanced by trapped air pockets, and to hydrodynamic uplift forces due to wave action. Any floating or mobile object in the nearshore/onshore areas can become floating debris, affecting structures in two ways: impact and water damming. Foundation soils and foundation systems are at risk from shear- and liquefaction-induced scour, unless designed appropriately. DOI: 10.1061/(ASCE)0733-950X(2007)133:6(463) CE Database subject headings: Storm surge; Hurricanes; Tsunamis; Coastal structures; Hydraulic loads; Debris; Structural failures. more...
- Published
- 2007
12. A Lagrangian trajectory view on transport and mixing processes between the eye, eyewall, and environment using a high-resolution simulation of Hurricane Bonnie (1998)
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Cram, Thomas A., Persing, John, Montgomery, Michael T., and Braun, Scott A.
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Hurricane Bonnie, 1998 -- Research ,Hurricanes -- United States ,Hurricanes -- Analysis ,Lagrangian functions -- Usage ,Atmospheric research ,Earth sciences ,Science and technology - Abstract
The transport and mixing characteristics of a large sample of air parcels within a mature and vertically sheared hurricane vortex are examined. Data from a high-resolution (2-km horizontal grid spacing) numerical simulation of real-case Hurricane Bonnie (1998) are used to calculate Lagrangian trajectories of air parcels in various subdomains of the hurricane (namely, the eye, eyewall, and near environment) to study the degree of interaction (transport and mixing) between these subdomains. It is found that 1) there is transport and mixing from the low-level eye to the eyewall that carries air possessing relatively high values of equivalent potential temperature ([[theta].sub.e]), which can enhance the efficiency of the hurricane heat engine; 2) a portion of the low-level inflow of the hurricane bypasses the eyewall to enter the eye, and this air both replaces the mass of the low-level eye and lingers for a sufficient time (order 1 h) to acquire enhanced entropy characteristics through interaction with the ocean beneath the eye; 3) air in the mid- to upper-level eye is exchanged with the eyewall such that more than half the air of the eye is exchanged in 5 h in this case of a sheared hurricane; and 4) that one-fifth of the mass in the eyewall at a height of 5 km has an origin in the mid- to upper-level environment where [[theta].sub.e] is much less than in the eyewall, which ventilates the ensemble average eyewall [[theta].sub.e] by about 1 K. Implications of these findings for the problem of hurricane intensity forecasting are briefly discussed. more...
- Published
- 2007
13. Storm surge simulations for Hurricane Hugo (1989): on the significance of inundation areas
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Dietsche, Daniel, Hagen, Scott C., and Bacopoulos, Peter
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Hurricane Hugo, 1989 -- Analysis ,Flood relief -- Analysis ,Hurricanes -- Analysis ,Engineering and manufacturing industries ,Science and technology - Abstract
The storm surge generated by Hurricane Hugo (1989) is reproduced for the purposes of (1) evaluating the significance of including inland flooding areas and corresponding levels of spatial resolution and (2) assessing the spatial variability of near-inlet boundary forcings with respect to storm surge hydrographs. The study focuses on the coastal regions of South Carolina, incorporating inundation areas between Charleston and Shallotte Inlet and including Winyah Bay and the Waccamaw River. The region of interest is modeled with five variations of an unstructured, finite-element mesh, including a localized coarse grid with and without floodplains, a localized fine grid with and without floodplains, and a large-domain approach that includes floodplains and the continental shelf and deep ocean. Simulation results demonstrate that the inclusion of inland flooding areas significantly improves the description of storm surge generation within coastal regions. While the large-domain approach is shown to be beneficial, it is determined that the coarse mesh resolution of the floodplains is sufficient. Computed water surface elevations at specific locations surrounding Winyah Bay Inlet indicate that storm surge hydrographs are highly spatially dependent near inlets, as opposed to the astronomical tides, which exhibit minimal variance in space around the inlet environment. DOI: 10.1061/(ASCE)0733-950X(2007)133:3(183) CE Database subject headings: Storm surges; Two-dimensional models; Hydrodynamics; Hurricanes; Computer aided simulation; Finite element method; Flood plains; Estuaries. more...
- Published
- 2007
14. Observed boundary layer wind structure and balance in the hurricane core. Part I: Hurricane Georges
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Kepert, Jeffrey D.
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Hurricane Georges, 1998 -- Analysis ,Hurricanes -- Analysis ,Earth sciences ,Science and technology - Abstract
The GPS dropsonde allows observations at unprecedentedly high horizontal and vertical resolution, and of very high accuracy, within the tropical cyclone boundary layer. These data are used to document the boundary layer wind field of the core of Hurricane Georges (1998) when it was close to its maximum intensity. The spatial variability of the boundary layer wind structure is found to agree very well with the theoretical predictions in the works of Kepert and Wang. In particular, the ratio of the near-surface wind speed to that above the boundary layer is found to increase inward toward the radius of maximum winds and to be larger to the left of the track than to the right, while the low-level wind maximum is both more marked and at lower altitude on the left of the storm track than on the right. However, the expected supergradient flow in the upper boundary layer is not found, with the winds being diagnosed as close to gradient balance. The tropical cyclone boundary layer model of Kepert and Wang is used to simulate the boundary layer flow in Hurricane Georges. The simulated wind profiles are in good agreement with the observations, and the asymmetries are well captured. In addition, it is found that the modeled flow in the upper boundary layer at the eyewall is barely supergradient, in contrast to previously studied cases. It is argued that this lack of supergradient flow is a consequence of the particular radial structure in Georges, which had a comparatively slow decrease of wind speed with radius outside the eyewall. This radial profile leads to a relatively weak gradient of inertial stability near the eyewall and a strong gradient at larger radii, and hence the tropical cyclone boundary layer dynamics described by Kepert and Wang can produce only marginally supergradient flow near the radius of maximum winds. The lack of supergradient flow, diagnosed from the observational analysis, is thus attributed to the large-scale structure of this particular storm. A companion paper presents a similar analysis for Hurricane Mitch (1998), with contrasting results. more...
- Published
- 2006
15. Observed boundary layer wind structure and balance in the hurricane core. Part II: Hurricane Mitch
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Kepert, Jeffrey D.
- Subjects
Hurricane Georges, 1998 -- Analysis ,Hurricane Mitch, 1998 -- Analysis ,Hurricanes -- Analysis ,Earth sciences ,Science and technology - Abstract
Part I of this paper presented a detailed analysis of the boundary layer of Hurricane Georges (1998), based mainly on the newly available high-resolution GPS dropsonde data. Here, similar techniques and data are used to study Hurricane Mitch (1998). In contrast to Hurricane Georges, the flow in the middle to upper boundary layer near the eyewall is found to be strongly supergradient, with the imbalance being statistically significant. The reason for the difference is shown to be the different radial structure of the storms, in that outside of the radius of maximum winds, the wind decreases much more quickly in Mitch than in Georges. Hurricane Mitch was close to inertially neutral at large radius, with a strong angular momentum gradient near the radius of maximum winds. Kepert and Wang predict strongly supergradient flow in the upper boundary layer near the radius of maximum winds in this situation; the observational analysis is thus in good agreement with their theory. The wind reduction factor (i.e., ratio of a near-surface wind speed to that at some level further aloft) is found to increase inward toward the radius of maximum winds, in accordance with theoretical predictions and the analysis by Franklin et al. Marked asymmetries in the boundary layer wind field and in the eyewall convection are shown to be consistent with asymmetric surface friction due to the storm's proximity to land, rather than to motion. The boundary layer flow was simulated using Kepert and Wang's model, forced by the observed storm motion, radial profile of gradient wind, and coastline position; and good agreement with the observations was obtained. more...
- Published
- 2006
16. The effects of Hurricane Ivan on Perdido Key, Escambia County Florida
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Pate, Katrina M., Brevik, Eric C., and Vincent, Paul C.
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Hurricane Ivan, 2004 -- Analysis ,Hurricanes -- Analysis ,Science and technology ,Analysis - Abstract
ABSTRACT Hurricanes are extremely destructive forces of nature. Barrier islands often take the hardest hit when hurricanes make landfall because they are low lying land located right on the coast. [...] more...
- Published
- 2006
17. Potential vorticity diagnosis of a simulated hurricane. Part I: formulation and quasi-balanced flow
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Wang, Xingbao and Zhang, Da-Lin
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Hurricanes -- Analysis ,Atmospheric research -- Analysis ,Earth sciences ,Science and technology - Abstract
Because of the lack of three-dimensional (3D) high-resolution data and the existence of highly nonelliptic flows, few studies have been conducted to investigate the inner-core quasi-balanced characteristics of hurricanes. In this study, a potential vorticity (PV) inversion system is developed, which includes the nonconservative processes of friction, diabatic heating, and water loading. It requires hurricane flows to be statically and inertially stable but allows for the presence of small negative PV. To facilitate the PV inversion with the nonlinear balance (NLB) equation, hurricane flows are decomposed into an axisymmetric, gradient-balanced reference state and asymmetric perturbations. Meanwhile, the nonellipticity of the NLB equation is circumvented by multiplying a small parameter [epsilon] and combining it with the PV equation, which effectively reduces the influence of anticyclonic vorticity. A quasi-balanced [omega] equation in pseudoheight coordinates is derived, which includes the effects of friction and diabatic heating as well as differential vorticity advection and the Laplacians of thermal advection by both nondivergent and divergent winds. This quasi-balanced PV-[omega] inversion system is tested with an explicit simulation of Hurricane Andrew (1992) with the finest grid size of 6 km. It is shown that (a) the PV-[omega] inversion system could recover almost all typical features in a hurricane, and (b) a sizeable portion of the 3D hurricane flows are quasi-balanced, such as the intense rotational winds, organized eyewall updrafts and subsidence in the eye, cyclonic inflow in the boundary layer, and upper-level anticyclonic outflow. It is found, however, that the boundary layer cyclonic inflow and upper-level anticyclonic outflow also contain significant unbalanced components. In particular, a low-level outflow jet near the top of the boundary layer is found to be highly unbalanced (and supergradient). These findings are supported by both locally calculated momentum budgets and globally inverted winds. The results indicate that this PV inversion system could be utilized as a tool to separate the unbalanced from quasi-balanced flows for studies of balanced dynamics and propagating inertial gravity waves in hurricane vortices. more...
- Published
- 2003
18. Interaction between hurricane Florence (1988) and an upper-tropospheric trough
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Shi, Jinan Jong, Chang, Simon, and Raman, Sethu
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Hurricanes -- Analysis ,Atmospheric circulation -- Analysis ,Weather forecasting -- Research ,Cyclones -- Analysis ,Earth sciences ,Science and technology - Abstract
The Naval Research Laboratory's limited-area numerical prediction system, a version of Navy Operational Regional Atmospheric Prediction System, was used to investigate the interaction between Hurricane Florence (1988) and its upper-tropospheric environment. The model was initialized with the National Meteorological Center (now the National Centers for Environmental Prediction)/Regional Analysis and Forecasting Systems 2.5 [degrees] analysis at 0000 UTC 9 September 1988, enhanced by a set of Omega dropwindsonde data through a three-pass nested-grid objective analysis. Diagnosis of the 200-mb level structure of the 12-h forecast valid for 1200 UTC 9 September 1988 showed that the outflow layer was highly asymmetric with an outflow jet originating at approximately 3[degrees] north of the storm. In agreement with the result of an idealized simulation (Shi et al. 1990), there was a thermally direct, circum-jet secondary circulation in the jet entrance region and a thermally indirect one in a reversed direction in the jet exit region. In several previous studies, it was postulated that an approaching westerly jet had modulated the convection and intensity variations of Florence. In a variational numerical experiment in this study, the approaching westerly jet was flattened out by repeatedly setting the jet-level meridional wind component and zonal temperature perturbations to zero in the normal mode initialization procedure. Compared with the control experiment, the variational experiment showed that the sudden burst of Florence's inner core convection was highly correlated with the approaching upper-tropospheric westerly jet. These experiments also suggested that the approaching upper-tropospheric westerly jet was crucial to the intensification of Florence's inner core convection between 1000 and 1500 UTC 9 September, which occurred prior to the deepening of the minimum sea level pressure (from 997 to 987 mb) between 1200 UTC 9 September and 0000 UTC 10 September. Many earlier studies have attempted an explanation for the effect on tropical cyclones of upper-tropospheric forcings from the eddy angular momentum approach. The result of this study provides an alternative but complementary mechanism of the interaction between an upper-level westerly trough and a tropical cyclone. more...
- Published
- 1997
19. Practical modeling of hurricane surface wind fields
- Author
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Thompson, Edward F. and Cardone, Vincent J.
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Hurricanes -- Analysis ,Winds -- Models ,Engineering and manufacturing industries ,Science and technology - Abstract
Approaches for recreating hurricane surface winds in relation to ocean wave, surge, and current modeling are reviewed. A discrete numerical wind field model, based on original developments at New York University in the early 1970s and used extensively by the U.S. Army Corps of Engineers (CE) and others, is described in detail. Limitations of the model are also discussed. The CE model for hurricane surface wind fields has been a very useful tool in ocean response (OR) modeling for more than a decade. Recently, several aspects of the model were upgraded, including increased spatial resolution and capabilities for simulating a wider variety of radial pressure and wind profile forms. The upgraded features of the model are described, and their impact on hurricane simulations is illustrated with a hypothetical hurricane and with hurricanes Camille (1969) and Gilbert (1988). The upgrades are expected to lead to improvements in the accuracy of OR modeling, particularly for small, intense hurricanes and for well-documented storms with broad and/or multipeaked radial wind profiles. more...
- Published
- 1996
20. Assessing Opal's impact
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Greenwood, David J. and Hatheway, Darryl J.
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United States. Federal Emergency Management Agency -- Planning ,Hurricanes -- Analysis ,Hurricane protection -- Planning ,Business ,Engineering and manufacturing industries ,Science and technology - Abstract
The Federal Emergency Management Agency emergency response services have prepared maps representing the expected damage level in Florida once Hurricane Opal passes through the area. A geographic information system containing data on demographics and public works was used to generate maps showing the expected damage and impact zone information for specific coastal and inland counties. Computer simulation of coastal and inland flooding provided the necessary data for evacuation and transportation plans. more...
- Published
- 1996
21. Researchers at Texas A&M University Target Natural Science (Effects of Hurricane Irma On the Endangered Lower Keys Marsh Rabbit)
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Rabbits -- Analysis ,Hurricanes -- Analysis ,Health ,Science and technology - Abstract
2021 JAN 29 (NewsRx) -- By a News Reporter-Staff News Editor at Science Letter -- A new study on Science - Natural Science is now available. According to news reporting [...]
- Published
- 2021
22. Texas A&M University Researchers Provide New Data on Science [Revising evidence of hurricane strikes on Abaco Island (The Bahamas) over the last 700 years]
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Hurricanes -- Analysis ,Health ,Science and technology - Abstract
2020 OCT 30 (NewsRx) -- By a News Reporter-Staff News Editor at Science Letter -- A new study on science is now available. According to news reporting from Texas A&M [...]
- Published
- 2020
23. Studies from University of Miami Have Provided New Information about Atmosphere Research (Hurricane Boundary Layer Height Relative to Storm Motion from GPS Dropsonde Composites)
- Subjects
Global Positioning System -- Analysis ,Hurricanes -- Analysis ,Editors ,Global Positioning System ,Health ,Science and technology - Abstract
2019 AUG 2 (NewsRx) -- By a News Reporter-Staff News Editor at Science Letter -- Investigators publish new report on Atmosphere Research. According to news reporting out of Miami, United [...]
- Published
- 2019
24. Mesovortices, Polygonal Flow Patterns, and Rapid Pressure Falls in Hurricane-Like Vortices
- Author
-
KOSSIN, JAMES P. and SCHUBERT, WAYNE H.
- Subjects
Vortex-motion -- Analysis ,Hurricanes -- Analysis ,Earth sciences ,Science and technology - Abstract
The present work considers the two-dimensional barotropic evolution of thin annular rings of enhanced vorticity embedded in nearly irrotational flow. Such initial conditions imitate the observed flows in intensifying hurricanes. Using a pseudospectral numerical model, it is found that these highly unstable annuli rapidly break down into a number of mesovortices. The mesovortices undergo merger processes with their neighbors and, depending on initial conditions, they can relax to a monopole or an asymmetric quasi-steady state. In the latter case, the mesovortices form a lattice rotating approximately as a solid body. The flows associated with such vorticity configurations consist of straight line segments that form a variety of persistent polygonal shapes. Associated with each mesovortex is a local pressure perturbation, or mesolow. The magnitudes of the pressure perturbations can be large when the magnitude of the vorticity in the initial annulus is large. In cases where the mesovortices merge to form a monopole, dramatic central pressure falls are possible. more...
- Published
- 2001
25. Spiral Bands in a Simulated Hurricane. Part I: Vortex Rossby Wave Verification
- Author
-
CHEN, YONGSHENG and YAU, M. K.
- Subjects
Hurricanes -- Analysis ,Vortex-motion -- Analysis ,Waves -- Analysis ,Earth sciences ,Science and technology - Abstract
An initially axisymmetric hurricane was explicitly simulated using the high-resolution PSU-NCAR nonhydrostatic mesoscale model (MM5). Spiral potential vorticity (PV) bands that formed in the model were analyzed. It was shown that PV bands and cloud bands are strongly coupled. The PV anomalies in and at the top of the boundary layer interact with friction to produce upward motion that gives rise to the inner cloud bands. The propagation properties of the PV bands were studied and found to be consistent with predictions of vortex Rossby wave theory. In the control simulation with full physics, continuous generation of PV through latent heat release in the eyewall and spiral rainbands maintain a 'bowl-shape' PV field. Inward transport of' high PV by the vortex Rossby waves and the process of nonlinear mixing tend to increase the inner-core PV anti in turn intensify the hurricane. On the other hand, frictional and PV mixing processes acted linearly to spin clown the hurricane to a midlevel vortex in a dry run, which indicates that a monopolar PV structure is the asymptotic stable state in the absence of condensation. more...
- Published
- 2001
26. Data on Management Science Reported by Researchers at Kennesaw State University (Optimal location, capacity and timing of stockpiles for improved hurricane preparedness)
- Subjects
Management science -- Analysis ,Hurricanes -- Analysis ,Health ,Science and technology - Abstract
2016 APR 29 (NewsRx) -- By a News Reporter-Staff News Editor at Science Letter -- New research on Science is the subject of a report. According to news reporting out [...]
- Published
- 2016
27. Studying sediment cores in search for evidence of hurricanes (paleotempestology) at Moccasin pond, Bull's Island S.C
- Author
-
Tupper, Lee
- Subjects
Paleotempestology -- Analysis ,Hurricanes -- Analysis ,Science and technology ,Analysis - Abstract
A 300-year historical record of intense hurricane landfalls in S.C. has been created and will be used to compare the results from this first paleotempestological research done in S.C. at [...]
- Published
- 2005
28. 'Hurricane Effect' Felt in Trade Deficit; One-time Insurance Payments for Hurricanes Katrina, Rita Mask Continuing Decay in the U.S. Current Account Deficit
- Subjects
Hurricane Katrina, 2005 -- Analysis ,Balance of trade -- Analysis ,Hurricanes -- Analysis ,Business ,Science and technology - Abstract
WASHINGTON, Dec 16, 2005 (U.S. Newswire via COMTEX) -- Dona??t let today's announcement of a decrease in the U.S. current account deficit fool you. Economic Policy Institute economist Robert Scott's [...] more...
- Published
- 2005
29. Interagency Performance Evaluation Task Force - Repair Improvements for the New Orleans Hurricane Protection System
- Subjects
United States. National Science Foundation -- Analysis ,American Society of Civil Engineers ,Hurricane Katrina, 2005 -- Analysis ,Hurricanes -- Analysis ,Business ,Science and technology ,Analysis - Abstract
WASHINGTON, Dec 9, 2005 (U.S. Newswire via COMTEX) -- Comprehensive analysis to determine exactly what happened in the New Orleans hurricane and flood protection system during Hurricane Katrina is the [...] more...
- Published
- 2005
30. NOAA Climate Model Connects Greenhouse Gases, Hurricanes
- Subjects
Air pollution -- Analysis ,Greenhouse gases -- Analysis ,Hurricanes -- Analysis ,Environmental issues ,Science and technology - Abstract
New climate simulations indicate that human-generated greenhouse gas emissions may be helping to warm the tropical region of the Atlantic where hurricanes arise, according to the Geophysics Fluid Dynamics Laboratory [...] more...
- Published
- 2006
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