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Damage Survey of Hurricane Andrew and Its Relationship to the Eyewall

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A damage map documenting Hurricane Andrew's destructive land fall over southern Florida is presented. Vectors that represent the direction of winds causing damage to trees and structures are shown along with an F-scale rating in order to assess the strength of the near-surface winds. It is hypothesized that increased surface roughness once the hurricane made landfall may have contributed to a surface wind enhancement resulting in the strongest winds ever estimated (F3) for a landfall hurricane. This intense damage occurred primarily during the "second" period of strong winds associated with the east side of the eyewall. For the first time, a well-defined circulation in the damage pattern by the second wind was documented. A superposition of radar data from Miami and Key West on top of the damage map provides the first detailed examination of the relationship between the eyewall and the surface flow field as estimated from the damage vectors.
... tropical cyclone eyewall | large eddy simulation | tornado-scale vortex O bservational studies based on the datasets from manned research flights that penetrated hurricane eyes and tropical cyclone (TC) damage surveys speculate upon the existence of the tornado-scale vortex in the TC boundary layer (TCBL) (1)(2)(3)(4)(5). Analysis of a dataset from GPS dropsondes released into TCs indicates that extreme low-level (0 km to 3 km) updrafts that are sometimes associated with extreme horizontal wind speeds can occur in the TCBL, also suggesting the existence of the small-scale (∼1 km) vortex in the TCBL (6,7). ...
... TCs at landfall often spawn tornadoes in outer rainbands (26,27), but a few studies based on limited data from manned research flights penetrating hurricane eyes, the TC damage survey, and GPS dropsondes speculate that the tornado-scale vortex exists in the turbulent boundary layer of the intense eyewall convection of TCs (1)(2)(3)(4)(5). In this study, we conducted a numerical experiment in which the complicated interactions of the largescale background flow, TC vortex, mesoscale organization, down to fine-scale turbulent eddies, are allowed by using the LES technique in the WRF model. ...
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Significance Tornado-scale vortices in the intense tropical cyclone eyewall have been speculated upon for more than two decades, but their small horizontal scale, their fast movement, and the associated severe turbulence make them very difficult to observe directly, except for the case of Hurricane Hugo (1989) in the Atlantic basin. Using the Advanced Weather Research and Forecast large eddy simulation framework with the unprecedented horizontal grid size of 37 m, the numerical experiment in this study confirms the existence of simulated tornado-scale vortices similar to the Hugo case in the turbulent eyewall boundary layer and further suggests that tornado-scale vortices are prevalent at the inner edge of the intense eyewall convection.
... Moreover, compared to numerical flux simulations with the PBL scheme in mesoscale models (e.g., Hong and Pan 1996;Hong et al. 2006;Hong 2010), some of the fluxes associated with roll vortices can be about 2-3 times greater (Morrison et al. 2005;Zhu 2008b; Gao and Ginis 2016). Strong fluxes induced by roll vortices change the hurricane structure and finally impact hurricane damage through intense surface winds (Saffir 1973;Wakimoto and Black 1994). ...
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Roll vortices are a series of large-scale turbulent eddies that nearly align with the mean wind direction and prevail in the hurricane boundary layer. In this study, the one-way nested WRF-LES model simulation results from Li et al. (J Atmos Sci 78(6):1847–1867, https://doi.org/10.1175/JAS-D-20-0270.1, 2021) are used to examine the structure and generation mechanism of roll vortices and associated coherent turbulence in the hurricane boundary layer during the landfall of Hurricane Harvey from 00 UTC 25 to 18 UTC 27 August 2017. Results indicate that roll vortices prevail in the hurricane boundary layer. The intense roll vortices and associated large turbulent eddies above them (at a height of ~ 200 to 3000 m) accumulate within a hurricane radius of 20–40 km. Their intensity is proportional to hurricane intensity during the simulation period. Before and during hurricane landfall, strong inflow convergence leads to horizontal advection of roll vortices throughout the entire hurricane boundary layer. Combined with the strong wind shear, the strongest roll vortices and associated large turbulent eddies are generated near the eyewall with suitable thermodynamic (Richardson number at around − 0.2 to 0.2) and dynamic conditions (strong negative inflow wind shear). After landfall, the decayed inflow weakens the inflow convergence and quickly reduces the strong roll vortices and associated large turbulent eddies. Diagnosis of vertical turbulent kinetic energy indicates that atmospheric pressure perturbation, caused by horizontal convergence, transfers the horizontal component of turbulence to the vertical component with a mean wavelength of about 1 km. The buoyancy term is weak and negative, and the large turbulent eddies are suppressed.
... The landing of tropical cyclones (TCs) are often accompanied by strong gusts and heavy rainfall, and can even cause mudslides, landslides, and many other disasters, posing a great threat to the lives and property near the coastlines (Pielke and Landsea, 1998;Pielke et al., 2008;Zhang et al., 2009;Liang et al., 2021;Wang et al., 2021;Zhao et al., 2022). Significant variability in damage patterns has been found after the passing of intense TCs, which indicates that the damage caused by TC is not only related to the sustained strong wind but also the localized strong gusts (Wakimoto and Black, 1994;Wurman and Kosiba, 2018). Since the mechanisms on the generation and evolution of strong wind gusts are complicated and have not been fully understood, wind gust forecast is a major challenge for disaster prevention and mitigation in coastlines affected by TCs (Krayer and Marshall, 1992;Black et al., 1999;Harper et al., 2010;Wurman and Kosiba, 2018). ...
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It has been demonstrated that the tornado-scale vortex (TSV) is one of the fine-scale structures associated with extreme updrafts in the tropical cyclone boundary layer (TCBL), but the relationship between surface wind gusts and TSVs is still unclear. In this study, the one-second model output simulated in the Weather Research and Forecast (WRF) model with the large eddy simulation (WRF-LES) is used to investigate the relationships between TSVs and surface wind gusts. Results show that surface wind gust factors in the regions where TSVs are prevalent are significantly larger than those in other regions. 88% of the maximum gust factors associated with TSVs (vertical velocity larger than 20 m s−1) are larger than 1.25 (gust factors larger than 1.25 account for only 1% of the 1-min gust factors in the TC inner core), and the mean maximum 1-min gust factor associated with a TSV is larger than 1.3, while the mean 1-min gust factor in the TC inner core is only 1.1. The surface gust factors associated with TSVs in tropical cyclone eyewall can reach about 1.8, which can cause severe surface wind hazards. This study suggests that potential risk will increase in the regions where TSVs are prevalent because of the large wind gusts and gust factors. Finer real-time observations are needed to monitor the evolution of TSVs for improving the operational TC-related surface gust warnings.
... Damage assessments after hurricanes or other disasters provide information about structural failure mechanisms and the capacity of a structure to resist extreme environmental conditions. Previous field studies after Hurricane Andrew (1992), Hurricane Katrina (2005), Hurricane Ike (2008), and other US storms identified wind, wave, and surge damage to near-coast residential structures, facilities, and transportation infrastructure (e.g., Wakimoto and Black 1994;Chaney 2007;Fritz et al. 2007;Robertson et al. 2007;Gurley and Masters 2011;Rogers et al. 2011;Kennedy et al. 2011). Field investigations after Hurricane Sandy documented the extent of damage and identified local features such as surviving dunes that protected inland structures from wave and surge damage during the storm (e.g., Irish et al. 2013;Tomiczek et al. 2017). ...
... Just before 1600 UTC, the cyclone reached Malta when DC initiation was detected close to the centre (Figures 1f and 7h). This sudden DC initiation over Malta may be attributed to surface friction and the low-level mass convergence (Wakimoto and Black, 1994), while no significant change to the DLS intensity took place to tilt the cyclone (Figure 8f). The vortex tilt remained at less than 50 km during the lifetime of the cyclone and for this reason, its direction fluctuated constantly (Figure 8f), mostly found to the right of the DLS vector pointing south-southeast during the DC activity. ...
Article
This study aims at understanding how deep convection is organized and contributes to the intensification of 9 Mediterranean tropical‐like cyclones which developed between 2005 and 2018. Through a multi‐satellite approach, a combination of infrared and microwave diagnostics provides insights into the temporal and spatial evolution of deep convection. ERA5 reanalysis complements the remote‐sensing observations and is used to compute the vertical wind shear and vortex tilt to investigate their interactions with deep convection. Results show that vertical wind shear and topography have an important impact on the organization of deep convection and the symmetry of the cyclones. Only a fraction of these cyclones experienced intense convective activity close to their centres and we show that persistent deep convection in the upshear quadrants led to intensification periods. Convective activity solely in the downshear quadrants was not linked to intensification periods, while short‐lived hurricane‐like structures develop only during symmetric convective activity, leading to cyclone intensification in some of the cases. Finally, a classification of the Mediterranean tropical‐like cyclones is proposed based on the evolution of deep convection and their intensification periods.
... But they are lacking in important ways for risk assessment. The models lack information on key damaging features such as accurate TC size, precipitation and eye-wall replacement cycles (Wakimoto and Black, 1994). Statistical models also may be susceptible to physical inconsistencies between variables and from the lack of spatial and temporal coherence of the damaging wind fields and intense rainfall, particularly over complex terrain. ...
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Populations and property values are increasing in tropical cyclone prone regions, driving up repair and replacement costs following a tropical cyclone impact. Climate change influences on tropical cyclones and sea levels will only exacerbate these rises. For example, Australia's Severe Tropical Cyclone Debbie in 2017 was one of the most destructive cyclones to make landfall in Australia since Tropical Cyclone Tracy in 1974. The primary impacts of Cyclone Debbie were due to extreme short duration intense wind driven rainfall and widespread major flooding, both linked to uncharacteristically warm sea surface temperatures. Studying the impact of climate change on tropical cyclones is limited by the lack of well observed historical events. Traditional hazard risk assessment approaches are limited since they are primarily based on statistical models which only deal with single meteorological hazards, or use simplified parameterized relationships when more than one phenomenon is included. Here we explore the value of dynamical models for creating targeted, detailed, and physically plausible multi-hazard tropical cyclone scenarios, through the development of a modeling system that i) retains a high degree of simulation control, ii) is globally applicable, and iii) is responsive to climate variability and change. Application of the modeling system to a thermodynamic climate change scenario finds that the tropical cyclone penetrates much further inland with a marked expansion of the heavy rainfall area, resulting in significantly larger areas subjected to damaging and destructive wind speeds and rainfall totals capable of producing flash and riverine flooding.
... Damage surveys after landfalling typhoon/hurricane have shown interesting damage patterns of scattered debris and trees. They exhibit significant periodicity in damage with scale near 500 m and even as small as 10-200 m (Fujita, 1992;Wakimoto et al., 1994;Powell et al., 1996;Wurman et al., 1998). Generally, these periodical damages have been attributed to small-scale tornados or low-level jets (LLJs). ...
... One of the major TC threats is damaging winds. Uneven damage patterns often show horizontal scales ranging from a few hundred meters to several kilometers (Wakimoto and Black, 1994;Wurman and Kosiba, 2018), suggesting that TC threats are associated with both sustained winds and gusts. The latter are believed to result from small-scale coherent structures in the TC boundary layer (Wurman and Winslow, 1998;Morrison et al., 2005;Lorsolo et al., 2008;Kosiba et al., 2013;Kosiba and Wurman, 2014). ...
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A tornado-scale vortex in the tropical cyclone (TC) boundary layer (TCBL) has been observed in intense hurricanes and the associated intense turbulence poses a severe threat to the manned research aircraft when it penetrates hurricane eyewalls at a lower altitude. In this study, a numerical experiment in which a TC evolves in a large-scale background over the western North Pacific is conducted using the Advanced Weather Research and Forecast (WRF) model by incorporating the large-eddy simulation (LES) technique. The simulated tornado-scale vortex shows features similar to those revealed with limited observational data, including the updraft–downdraft couplet, the sudden jump of wind speeds, the location along the inner edge of the eyewall, and the small horizontal scale. It is suggested that the WRF–LES framework can successfully simulate the tornado-scale vortex with grids at a resolution of 37 m that cover the TC eye and eyewall. The simulated tornado-scale vortex is a cyclonic circulation with a small horizontal scale of ∼1 km in the TCBL. It is accompanied by strong updrafts (more than 15 m s⁻¹) and large vertical components of relative vorticity (larger than 0.2 s⁻¹). The tornado-scale vortex favorably occurs at the inner edge of the enhanced eyewall convection or rainband within the saturated, high-θe layer, mostly below an altitude of 2 km. In nearly all the simulated tornado-scale vortices, the narrow intense updraft is coupled with the relatively broad downdraft, constituting one or two updraft–downdraft couplets, as observed by the research aircraft. The presence of the tornado-scale vortex also leads to significant gradients in the near-surface wind speed and wind gusts.
... Research on hurricane landfall and the patterns of destruction left by these extreme events has also led to the realisation that roll vortices are commonly generated where high shear flows traverse the ocean-land boundary where they strongly modulate surface wind speed (Wurman & Winslow, 1998;Morrison et al. 2005;Svensson et al. 2017). Rolls have been observed with wavelengths ranging from sub-kilometre to 2 to 4 km wavelengths between counter-rotating convective bands and they account for damage swaths extending for several hundred metres in the mean wind direction (Wakimoto & Black, 1994). ...
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Exploration for aeolian diamond placers within the southern Sperrgebiet requires a thorough understanding of aeolian transport across a broad range of scales from a systemic regional level to a micro-topographic-scale at the individual particle level. Within this arid zone the transport of coarse-grained aeolian bedload, including diamonds, is driven by the impact of saltating sandflow, which produces a uniquely characteristic diamond dispersal pattern as well as a variety of coarse-grained bedload features, textures and fabrics. For the first time the Namibian Aeolian System (NAS : see Annex 1 for abbreviations) which runs along the entire continental margin from the Orange River in the south to southern Angola in the north can be studied within the context of the recently discovered Benguela Low-Level Coastal Jet (BLLCJ). The structures produced in response to the hydraulic behaviour of the BLLCJ flow are shown to influence strongly the location of zones of high-energy erosion and aeolian sand accumulation throughout the system. The boundary conditions of the Namib Aeolian Erosion Basin are redefined to include the influence of the BLLCJ on the architecture and dynamics of sandflow pathways through this high-energy aeolian erosion landscape. Empirical sandflow measurements were previously used to identify narrow, linearly extensive Aeolian Transport Corridors characterised by high sandflow conditions. The corridors are commonly marked by the development of mono-trains of large barchan dunes along their length. The advent of Google Earth Engine time-lapse video provides an observational platform enabling spatial and temporal changes in sandflow and bedforms to be examined over a 32 year period. It thus provides many new insights into sandflow-dune and dune-dune interaction throughout this large-scale system down to the resolution of individual protobarchan genesis. The influence of the hydraulic behaviour of the BLLCJ flow together with localised effects of topography on surface wind flow structure is examined through analysis of a unique 10 km wide regional Airborne Laser Scanner (ALS) dataset stretching 170 km from Chameis Bay in the south to Schmidtfeld, to the north of Lüderitz. Aeolian bedforms and erosional features and patterns of coarse-grained aeolian bedload textural features and fabrics are mapped in detail throughout the Sperrgebiet. Changes in bedform interaction are shown to reflect variation in the pattern of surface flow created by localised topographic blocking and steering effects. The new system-wide perspective on the pattern of sandflow that feeds into, and maintains, the present-day Namib Sand Sea shows clear evidence of the influence of the BLLCJ as well as a variety of different types of vortices, which is a newly recognised element in the boundary conditions of this high-energy system. It is concluded that favourable conditions exist for the formation of horizontal rolls and vortex structures of varying length-scales within the Marine Boundary Layer (MBL) associated with the BLLCJ. It is proposed that these strongly influence both the development of the erosional aeolian landscape and the pattern of bedforms that develop within Aeolian Transport Corridors in response to surface wind flow over complex topography.
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Miami-Dade County is highly susceptible to storm surge flooding. The current Federal Insurance Rate Map (FIRM), used to determine flood insurance rates for buildings, is an excellent resource yet lacks attributes that could provide a finer-resolution of actual vulnerability for building level characteristics from one parcel to the next within the same flood zone. This study developed a novel Storm Surge Building Vulnerability (SSBV) model to provide initial protocols for developing storm surge vulnerability county maps. The model was tested on transversal sections of 1254 buildings selected from Miami Beach, East Little Havana, and Sweetwater. Buildings in the county were determined to be moderately vulnerable to storm surge flooding. High-rises, masonry buildings, and buildings whose first habitable space is elevated above the ground constitute the majority of low and very low vulnerability buildings, but 97% of high and very high vulnerability buildings are between 0 and 2 story tall and three-quarters of these have slab-on-grade finished floor elevation. Our model exposes limitations of FIRM designated hazard zones: buildings within the same zone exhibit different vulnerability characteristics. This indicates the importance of creating initial protocols to consider upgrading flood insurance rate requirement from zonal categories to individual building level.
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