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The characteristics of tropical cyclone vertical wind profiles and their associated wind speed peaks below 1.5 km were examined through the use of a large number of GPS dropwindsondes (GPS sondes) and radar-derived velocity-azimuth display (VAD) profiles. Composite wind profiles were generated to document the mean structure of tropical cyclone vertical wind profiles and their changes with storm-relative position. Composite profiles were observed to change as the radius decreased inward toward the radius of maximum winds. Profiles also varied between three azimuthal sectors. At landfall, wind profiles exhibited changes with radial distance and differences were observed between those within offshore and onshore flow regimes. The observations support a general reduction in boundary layer depth with decreasing radial distance. Wind profiles with peaks at low altitudes were typically confined to radii less than 60 km, near and radially inward from the radius of maximum winds. Wind speed maxima, when scaled by a layer mean wind, decreased in magnitude as the radius decreased. At landfall, composite profiles showed a distinct low-level wind speed maximum in the eyewall region with significant differences between the onshore and offshore flow regimes. [ABSTRACT FROM AUTHOR]

Over the last decade substantial improvements have been made in our ability to observe the tropical cyclone boundary layer. Low-level wind speed maxima have been frequently observed in Global Positioning System dropwindsonde (GPS sonde) profiles. Data from GPS sondes and coastal Doppler radars were employed to evaluate the characteristics of tropical cyclone vertical wind profiles in open ocean conditions and at landfall. Changes to the mean vertical wind profile were observed azimuthally and with decreasing radial distance toward the cyclone center. Wind profiles within the hurricane boundary layer exhibited a logarithmic increase with height up to the depth of the wind maximum. [ABSTRACT FROM AUTHOR]

In 2005, wind-induced structural damage from Hurricane Katrina resulted in extensive energy supply disruptions across the Gulf of Mexico. In this paper, we examine the resilience of these systems with a particular emphasis on the electric power delivery systems. We investigate the correlations of the power outage data with weather parameters such as wind speed, rainfall, and storm surge. We examine the resilience and recovery of the electric delivery system spatially and temporally and compare the results with other natural disasters. We conclude that the behavior of the delivery systems under hurricane loadings is affected by rainfall and storm surge as well as wind speed. Widespread failures may occur at wind speeds less than predicted peak values. [ABSTRACT FROM AUTHOR]

In 2005, Hurricane Rita caused significant damage to the energy infrastructure in the Gulf of Mexico region. In the context of this investigation, the “energy infrastructure” refers to the offshore oil platforms, refineries, and gasoline supply stations in the region, often referred to as the “petroleum infrastructure,” the natural gas supply lines, and the delivery of electric power. In this paper, we examine the structural damage to the networks as defined by restoration, resilience, and fragility with a focus on the analysis of the electric power delivery disruptions. Our concern is not on the evaluation of risk, but rather to provide those who assess hurricane risk with relevant structural damage prediction models. We provide correlations of hurricane wind speed data with outages. We conclude that high winds alone can create significant damage to the energy infrastructure system. [ABSTRACT FROM AUTHOR]

Radial profiles of surface winds measured by the Stepped Frequency Microwave Radiometer (SFMR) are compared to radial profiles of flight-level winds to determine the slant ratio of the maximum surface wind speed to the maximum flight-level wind speed, for flight altitude ranges of 2–4 km. The radius of maximum surface wind is found on average to be 0.875 of the radius of the maximum flight-level wind, and very few cases have a surface wind maximum at greater radius than the flight-level maximum. The mean slant reduction factor is 0.84 with a standard deviation of 0.09 and varies with storm-relative azimuth from a maximum of 0.89 on the left side of the storm to a minimum of 0.79 on the right side. Larger slant reduction factors are found in small storms with large values of inertial stability and small values of relative angular momentum at the flight-level radius of maximum wind, which is consistent with Kepert’s recent boundary layer theories. The global positioning system (GPS) dropwindsonde-based reduction factors that are assessed using this new dataset have a high bias and substantially larger RMS errors than the new technique. A new regression model for the slant reduction factor based upon SFMR data is presented, and used to make retrospective estimates of maximum surface wind speeds for significant Atlantic basin storms, including Hurricanes Allen (1980), Gilbert (1988), Hugo (1989), Andrew (1992), and Mitch (1998). [ABSTRACT FROM AUTHOR]

Tropical cyclones cause extensive tree mortality and damage to forested ecosystems. A number of patterns in tropical cyclone frequency and intensity have been identified. There exist, however. few studies on the dynamic impacts of historical tropical cyclones at a continental scale. Here, we synthesized field measurements, satellite image analyses, and empirical models to evaluate forest and carbon cycle impacts for historical tropical cyclones from 1851 to 2000 over the continental U.S. Results demonstrated an average of 97 million trees affected each year over the entire United States, with a 53-Tg annual biomass loss, and an average carbon release of 25 Tg y-1. Over the period 1980-1990. released CO2 potentially offset the carbon sink in forest trees by 9-18% over the entire United States. U.S. forests also experienced twice the impact before 1900 than after 1900 because of more active tropical cyclones and a larger extent of forested areas. Forest impacts were primarily located in Gulf Coast areas, particularly southern Texas and Louisiana and south Florida, while significant impacts also occurred in eastern North Carolina. Results serve as an important baseline for evaluating how potential future changes in hurricane frequency and intensity will impact forest tree mortality and carbon balance. [ABSTRACT FROM AUTHOR]

Southern Louisiana is characterized by low-lying topography and an extensive network of sounds, bays, marshes, lakes, rivers, and inlets that permit widespread inundation during hurricanes. A basin- to channel-scale implementation of the Advanced Circulation (ADCIRC) unstructured grid hydrodynamic model has been developed that accurately simulates hurricane storm surge, tides, and river flow in this complex region. This is accomplished by defining a domain and computational resolution appropriate for the relevant processes, specifying realistic boundary conditions, and implementing accurate, robust, and highly parallel unstructured grid numerical algorithms. The model domain incorporates the western North Atlantic, the Gulf of Mexico, and the Caribbean Sea so that interactions between basins and the shelf are explicitly modeled and the boundary condition specification of tidal and hurricane processes can be readily defined at the deep water open boundary. The unstructured grid enables highly refined resolution of the complex overland region for modeling localized scales of flow while minimizing computational cost. Kinematic data assimilative or validated dynamic-modeled wind fields provide the hurricane wind and pressure field forcing. Wind fields are modified to incorporate directional boundary layer changes due to overland increases in surface roughness, reduction in effective land roughness due to inundation, and sheltering due to forested canopies. Validation of the model is achieved through hindcasts of Hurricanes Betsy and Andrew. A model skill assessment indicates that the computed peak storm surge height has a mean absolute error of 0.30 m. [ABSTRACT FROM AUTHOR]

Hurricane Donna, the only major hurricane to strike the United States during the 1960 Atlantic hurricane season, passed over the middle Florida Keys near Sombrero Key before making landfall southeast of Naples, near Goodland, Florida, on 10 September at approximately 1600 UTC. This study makes detailed retrospective surface wind analyses of Hurricane Donna utilizing the National Oceanic and Atmospheric Administration (NOAA) Hurricane Research Division's (HRD) H*Wind surface wind analysis system. Analyses were produced at intervals of 6 h between 1800 UTC 9 September and 1200 UTC 11 September 1960 while the hurricane was close to and over Florida. These analyses depict the storm track as well as the distribution and extent of tropical storm force, 50 kt (25.7 m s[sup -1] ), and the hurricane-force wind radii throughout this time period and include new methodologies for adjusting aircraft flight-level data to the surface in the tropical cyclone core environment. Algorithms were developed to account for the effects of eyewall tilt and the warm core structure typical of tropical cyclones. Additional methods were developed using global positioning system (GPS) dropwindsondes (sondes) to more accurately adjust boundary layer winds to equivalent surface winds. The Kaplan–DeMaria Inland Wind Decay Model was also used for the first time to adjust landfall data being input into the H*Wind system. These data were used to generate low-weighted background fields that helped generate postlandfall wind field analyses of Hurricane Donna. Finally, swaths of peak winds, duration of hurricane- and major hurricane–force winds, and wind steadiness were produced to facilitate damage assessment. The information provided by these objective analyses is significantly more detailed than the more limited descriptions of peak winds, storm position, and minimum central pressure available in the National Hurricane Center's (NHC) hurricane database archive (HURDAT). [ABSTRACT FROM AUTHOR]

The surface wind fields of several tropical cyclones which impacted Florida Bay and the Surrounding coastal areas were reconstructed by the Hurricane Research Division (HRD) of the National Oceanographic and Atmospheric Administration. These cyclones provided the forcing for significant changes in water-levels, waves, and currents, resulting in sediment transport, deposition, and other physical processes affecting the bay. In addition, tropical cyclones had direct and indirect effects on plant and animal life in the bay and the surrounding coastal areas, such as the Florida Keys and Everglades. The HRD wind fields are being made available in gridded form for use in hindcasts, which may help researchers to estimate the potential impacts of future tropical cyclones on the south Florida ecosystem, especially in relation to Florida Bay. The tropical cyclones investigated represent vastly different scenarios for the type of events that might be expected over extreme south Florida. The reconstructed storms range in intensity from Tropical Storm Gordon of 1994 to the Labor Day Hurricane of 1935 (the United States' most intense hurricane at landfall). This paper summarizes the methods used to reconstruct tropical cyclone surface wind fields and provides examples of their circulation features and wind swaths. Comparisons of winds to observed damage are also presented for three major hurricanes. The wind fields for all of these tropical cyclones are being made available to researchers as graphical products and gridded data sets on a Web site maintained by HRD (www.aoml.noaa.gov/hrd). [ABSTRACT FROM AUTHOR]

Comments on the differences between the observed and simulated surface wind distributions during the Hurricane Andrew in 1992. Distribution of surface winds at landfall; Standard framework for surface winds in hurricanes; Adjustment to maximum sustained wind and comparison to observed maxima.

Surface wind observations analyzed by the Hurricane Research Division (HRD) were compared to those computed by the parametric wind model used in the National Weather Service Sea, Lake, and Overland Surges from Hurricanes (SLOSH) model's storm surge computations for seven cases in five recent hurricanes. In six cases, the differences between the SLOSH and HRD surface peak wind speeds were 6% or less, but in one case (Hurricane Emily of 1993) the SLOSH computed peak wind speeds were 15% less than the HRD. In all seven cases, statistics for the modeled and analyzed wind fields showed that for the region of strongest winds, the mean SLOSH wind speed was 14% greater than that of the HRD and the mean inflow angle for SLOSH was 19° less than that of the HRD. The radii beyond the region of strongest winds in the seven cases had mean wind speed and inflow angle differences that were very small. The SLOSH computed peak storm surges usually compared closely to the observed values of storm surge in the region of the maximum wind speeds, except Hurricane Emily where SLOSH underestimated the peak surge. HRD's observation-based wind fields were input to SLOSH for storm surge hindcasts of Hurricanes Emily and Opal (1995). In Opal, the HRD input produced nearly the same computed storm surges as those computed from the SLOSH parametric wind model, and the calculated surge was insensitive to perturbations in the HRD wind field. For Emily, observation-based winds produced a computed storm surge that was closer to the peak observed surge, confirming that the computed surge in Pamlico Sound was sensitive to atmospheric forcing. Using real-time, observation-based winds in SLOSH would likely improve storm surge computations in landfalling hurricanes affected by synoptic and mesoscale factors that are not accounted for in parametric models (e.g., a strongly sheared environment, convective asymmetries, and stably stratified boundary layers). An accurate diagnosis of storm surge... [ABSTRACT FROM AUTHOR]

Hurricanes Erin, Opal, Luis, Marilyn, and Roxanne were the most destructive hurricanes of 1995. At landfall, Luis and Marilyn contained maximum sustained winds (marine exposure) estimated at near 60 and 46 m s[sup-1], respectively. The strongest landfalling storm of the 1995 season, Luis, decreased in intensity from a category 4 to 3 on the Saffir-Simpson scale shortly before the eyewall crossed the Islands of Antigua, Barbuda, St. Kitts-Nevis, St. Barthelemy, St. Martin, and Anguilla. Hurricane Marilyn strengthened as it approached the U.S. Virgin Islands, with St. Thomas bearing the brunt of the north and south eyewall winds of 46 m s[sup-1] (marine exposure) and St. Croix being affected by the relatively weak western eyewall peak winds of 35-40 m s[sup-1] (marine exposure). For Luis and Marilyn only surface winds with marine exposures were analyzed because of unknown small-scale interactions associated with complex island terrain with 500-1000-m elevations. Wind engineering studies suggest that wind acceleration over blunt ridges can increase or 'speed up' winds by 20percent-80percent. Topographic effects were evident in damage debris analyses and suggest that an operational method of assessing terrain-induced wind gusts (such as a scaled down mesoscale model) is needed. After landfall as a marginal hurricane over central Florida, Hurricane Erin regained strength over the Gulf of Mexico with a well-defined radar reflectivity structure. Erin struck the Florida panhandle near Navarre Beach with maximum sustained surface winds of 35-40 m s[sup-1] affecting the Destin-Ft. Walton area. Hurricane Opal made landfall in nearly the identical area as Erin, with maximum sustained surface winds of 40-45 m s[sup-1], having weakened from an intensity of nearly 60 m s[sup-1] only 10 h earlier. Opal was characterized by an asymmetric structure that was likely related to cold front interaction and an associated midlevel southwesterly jet. Roxanne struck Cozumel... [ABSTRACT FROM AUTHOR]

Abstract: Hurricane hazard modeling has become a commonly used tool for assessing hurricane risk. The type of hurricane risk considered varies with the user and can be an economic risk, as in the case of the insurance and banking industries, a wind exceedance risk, a flood risk, etc. The most common uses for hurricane hazard models today include: [(i)] Simulation of wind speed and direction for use with wind tunnel test data to estimate wind loads vs. return period for design of structural systems and cladding. [(ii)] Estimation of design wind speeds for use in buildings codes and standards. [(iii)] Coastal hazard risk modeling (e.g. storm surge elevations and wave heights vs. return period). [(iv)] Insurance loss estimation (e.g. probable maximum losses, average annual losses). This paper presents an overview of the past and present work in hurricane modeling. The wind model is the key input to each of the examples presented above and is the focus herein. We discuss the evolution and current state of wind field modeling, modeling uncertainties, and possible future directions of the hurricane risk modeling process. [Copyright &y& Elsevier]