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We examine a recently developed physics-based tropical cyclone rainfall (TCR) model and apply it to assess the mechanisms that dominate the magnitude and spatial distribution of TC rainfall, with Hurricanes Isabel (2003) and Irene (2011) as study cases. We evaluate the TCR model using Weather and Research Forecasting (WRF) Model simulations. TCR-generated rainfall fields for the two storms compare well with WRF estimates in terms of both azimuthal mean and spatial distributions. When coupled with a hydrologic model, TCR generates flood peaks over the Delaware River basin for Irene as accurately as WRF. TCR accounts for four major rainfall mechanisms: surface frictional convergence, vortex stretching, interaction of the storm with topography, and interaction of the storm with large-scale baroclinity. We show that these rainfall mechanisms affected the rainfall pattern differently for Isabel and Irene. Frictional convergence is the dominant factor, while other mechanisms are also significant. The frictional convergence depends on the boundary layer formulation, which is relatively simple in TCR and may require calibration of boundary layer parameters. Furthermore, we find that the TC rainfall distribution is strongly dependent on the temporal and spatial variation of the TC wind field, mediated by the physical mechanisms represented by TCR. When coupled with various analytical wind models, TCR generally captures the rainfall distribution, with the Holland wind model performing the best. Given its high computational efficiency, TCR can be coupled with an analytical wind model, a hydrological model, and a TC climatology model to generate large numbers of synthetic events to assess the risk associated with TC rainfall and inland flooding. [ABSTRACT FROM AUTHOR]

When a hurricane undergoes extratropical transition (ET), its rainbands evolve from a circular and compact shape to a more elongated, fragmented, and dispersed configuration with an exposed circulation center. This study calculates five metrics to measure these spatial changes in reflectivity regions as Hurricane Isabel (2003) underwent ET. A mosaic of observations from the Weather Surveillance Radar-1988 Doppler (WSR-88D) network is compared to reflectivity simulated by the Advanced Research Weather Research and Forecasting (WRF-ARW) Model. Six simulations are performed by varying the cumulus and microphysics parameterizations to produce a range of reflectivity configurations. A bias correction is applied to model-simulated reflectivity prior to the calculation of spatial metrics because lower reflectivity values are generally underrepresented, while higher values are generally overrepresented. However, the simulation with Kain-Fritsch cumulus and Morrison two-moment microphysics overpredicts reflectivity by 3-4 dB Z at all levels. We demonstrate that the spatial metrics effectively capture structural changes as reflectivity regions became more fragmented and dispersed and the center became more exposed. In this case study, the results were more sensitive to the choice of cumulus physics, compared with the choice of microphysics. The Kain-Fritsch simulations produce shapes that are too circular and solid when compared with WSR-88D observations, as the hurricanes lack distinct outer rainbands. Simulations with Tiedtke cumulus produce an elongated main reflectivity region as in WSR-88D, but with separate inner and outer rainbands that are too dispersed and fragmented. These results demonstrate the value in measuring spatial patterns rather than assessing model performance using visual inspection alone. [ABSTRACT FROM AUTHOR]

ABSTRACT The mid-Atlantic region of the United States is susceptible to tropical cyclone hazards. Within the past 15 years this region has experienced Hurricane Isabel in 2003, Hurricane Irene in 2011 and several tropical storms. The region was also impacted by post-tropical Sandy in 2012. The perception of hurricane hazards among residents of the mid-Atlantic region has not been directly researched. Furthermore, there is a lack of research on the comprehension of information from hurricane warning graphics that influences hazard perception. This research used a total of eight hypothetical scenarios (four pairs) that varied storm track and storm size to assess risk perception of hurricane hazards and characteristics. Each scenario was represented using a four-panelled map featuring the National Hurricane Center's cone of uncertainty, a new storm surge map and a new damaging wind map created by the authors. A Qualtrics survey was used to collect responses to questions about concern for personal harm and evacuation intent. Residents of the region perceived falling trees, potential for damaging winds and the size of the storm to be the greatest threats. Scenarios depicting larger storms with track lines that moved inland were seen as more hazardous, resulting in greater concern and evacuation intent. Coastal residents showed greater concern about distance from the track for all scenarios and greater evacuation intent for larger storms compared to inland residents. [ABSTRACT FROM AUTHOR]

The long-term behavior of tropical cyclones in the prototype problem for cyclone intensification on an f plane is examined using a nonhydrostatic, three-dimensional numerical model. After reaching a mature intensity, the model storms progressively decay while both the inner-core size, characterized by the radius of the eyewall, and the size of the outer circulation-measured, for example, by the radius of the gale-force winds-progressively increase. This behavior is explained in terms of a boundary layer control mechanism in which the expansion of the swirling wind in the lower troposphere leads through boundary layer dynamics to an increase in the radii of forced eyewall ascent as well as to a reduction in the maximum tangential wind speed in the layer. These changes are accompanied by changes in the radial and vertical distribution of diabatic heating. As long as the aggregate effects of inner-core convection, characterized by the distribution of diabatic heating, are able to draw absolute angular momentum surfaces inward, the outer circulation will continue to expand. The quantitative effects of latitude on the foregoing processes are investigated also. The study provides new insight into the factors controlling the evolution of the size and intensity of a tropical cyclone. It provides also a plausible, and arguably simpler, explanation for the expansion of the inner core of Hurricane Isabel (2003) and Typhoon Megi (2010) than that given previously. [ABSTRACT FROM AUTHOR]

Hurricane Isabel (September 2003) was the largest, most damaging hurricane to hit Virginia in at least 70 years. Permanent plots established in a maturing upland hardwood forest in 2002 were resampled in 2004 to assess hurricane damage. Tree loss among stems ≥10 cm diameter breast high (dbh) varied from none in 7 of the 20 plots to 50% of stems and 83% of canopy cover in a plot hit by a local microburst. Loss was greater on ridges arid other higher elevation sites, and downwind of expanses of water. Loss was significantly higher in trees ≥60 cm dbh. Loss in Quercus velutina (46.6%) was significantly higher, and in Fagus grand ifolia (7.7%) and Acer rubrum (7.4%) loss was significantly lower than the overall loss rate (16.9%). The latter two species occurred mostly in the lower canopy and understory, where tree loss was generally lower. Among stems ≥2.5 cm dbh but <10 cm dbh, all loss was secondary damage from falling larger trees, but was significantly higher in Oxydencirum arboreum (36.4%) and significantly lower in Acer rubrum (3.6%) than the overall loss rate for this size class (11.0%). ilex opaca had a low loss rate in both larger and smaller size classes, but in both classes, difference from the overall rate was just short of the p < 0.05 level. [ABSTRACT FROM AUTHOR]

In September 2003, Hurricane Isabel created an inlet over 500 m wide and 10 m deep that connected the Atlantic Ocean and Pamlico Sound. This breach was subsequently filled with sediments dredged from the adjacent sound. The purpose of this study was to determine if the barrier island terrestrial plant communities were naturally re-establishing through primary succession. In 2006-2008, we compared plant communities, soil carbon and nitrogen, and Aeolian transport of sediments in undisturbed back-dunes, undisturbed shrub thickets, putative back-dunes, and putative shrub thickets. We found that species richness and evenness were low on the filled area relative to adjacent plant communities that had persisted through the storm. Plants on the filled area were almost entirely limited to a band of primarily Spartina patens found at the margin of the sound and there were no signs of establishing the typical zonation of back dune grasses, shrubs, and salt marsh. Evaluation of soil quality suggests that nutrients and organic material are not limiting recovery. Aeolian transport, however, was demonstrably higher across the filled area, where no dense stands of taller plants buffered the airflow. Plant re-establishment is suppressed by wind erosion inhibiting deposition of seeds. Recovery of the site will likely depend on the rhizomatous spread of S. patens from the sound shore. S. patens can then potentially facilitate the colonization of other species by buffering the wind and trapping seeds of other plants. Ironically, this slow recovery may benefit federally threatened bird species that require sparse vegetation for nesting success. [ABSTRACT FROM AUTHOR]

Abstract: The response of Chesapeake Bay to forcing from two hurricanes is investigated using an unstructured-grid three-dimensional hydrodynamic model SELFE. The model domain includes Chesapeake Bay, its tributaries, and the extended continental shelf in the mid-Atlantic Bight. The hurricanes chosen for the study are Hurricane Floyd (1999) and Hurricane Isabel (2003), both of which made landfall within 100km of the mouth of the Bay. The model results agree reasonably well with field observations of water level, velocity, and salinity. From the Bay’s water level response to the hurricanes, it was found that the storm surge in the Bay has two distinct stages: an initial stage set up by the remote winds and the second stage – a primary surge induced by the local winds. For the initial stage, the rising of the coastal sea level was setup by the remote wind of both hurricanes similarly, but for the second stage, the responses to the two hurricanes’ local winds are significantly different. Hurricane Floyd was followed by down-Bay winds that canceled the initial setup and caused a set-down from the upper Bay. Hurricane Isabel, on the other hand, was followed by up-Bay winds, which reinforced the initial setup and continued to rise up against the head of the Bay. From the perspective of volume and salt fluxes, it is evident that an oceanic saltwater influx is pushed into the Bay from the continental shelf by the remote wind fields in the initial stages of the storm surge for both Floyd and Isabel. In the second stage after the hurricane made landfall, the Bay’s local wind plays a key role in modulating the salinity and velocity fields through vertical mixing and longitudinal salt transport. Controlled numerical experiments are conducted in order to identify and differentiate the roles played by the local wind in stratified and destratified conditions. Down-estuary local wind stress (of Hurricane Floyd-type) tends to enhance stratification under moderate winds, but exhibits an increasing-then-decreasing stage when the wind stress increases. The up-estuary local wind stress (of Hurricane Isabel-type) tends to penetrate deeper into the water column, which reduces stratification by reversing gravitational circulation. To characterize mixing conditions in the estuary, a modified horizontal Richardson number that incorporates wind stress, wind direction, horizontal salinity gradient, and vertical eddy viscosity is used for both hurricanes. Finally, the direct precipitation of rainfall into the Bay during Hurricane Floyd appears to create not only a thin surface layer of low salinity but also a seaward barotropic pressure gradient that affects the subsequent redistribution of salinity after the storm. [Copyright &y& Elsevier]

The maximum surface wind speed is an important parameter for tropical cyclone operational analysis and forecasting, since it defines the intensity of a cyclone. Operational forecast centers typically refer the wind speed to a maximum 1- or 10-min averaged value. Aircraft reconnaissance provides measurements of surface winds; however, because of the large variation of winds in the eyewall, it remains unclear to what extent observing the maximum wind is limited by the sampling pattern. Estimating storm intensity as simply the maximum of the observed winds is generally assumed by forecasters to underestimate the true storm intensity. The work presented herein attempts to quantify this difference by applying a methodology borrowed from the observing system simulation experiment concept, in which simulated 'observations' are drawn from a numerical model. These 'observations' may then be compared to the actual peak wind speed of the simulation. By sampling a high-resolution numerical simulation of Hurricane Isabel (2003) with a virtual aircraft equipped with a stepped-frequency microwave radiometer flying a standard 'figure-four' pattern, the authors find that the highest wind observed over a flight typically underestimates the 1-min averaged model wind speed by 8.5%% ± 1.5%%. In contrast, due to its corresponding larger spatial scale, the 10-min averaged maximum wind speed is far less underestimated (1.5%% ± 1.7%%) using the same sampling method. These results support the National Hurricane Center's practice, which typically assumes that the peak 1-min wind is somewhat greater than the highest observed wind speed over a single reconnaissance aircraft mission. [ABSTRACT FROM AUTHOR]

INTRODUCTION: Previous studies have identified a number of demographic characteristics (e.g., age, income, level of education, household composition, and race or ethnicity) that affect hurricane evacuation. However, the magnitude and direction of these associations vary widely, even when the area of landfall or the intensity of the storm is similar. We propose that the associations of demographic characteristics and hurricane evacuation are modified by psychosocial factors such as social cohesion, social capital, and social control. Additional variability may be the result of the changing prevalence of these demographic variables over time or between study locations. METHODS: Ninety census blocks in three eastern North Carolina counties affected by Hurricane Isabel were selected probability proportionate to population and seven interviews were conducted at random locations within each of the selected blocks. Risk differences (RD) and 95% confidence intervals (CI) were produced for stratified data to test for heterogeneity. RESULTS: There was statistical evidence of effect measure modification on the additive scale of the effect of home type, homeownership, age, race, gender, marital status, and having children under age 18 living at home on hurricane evacuation based on Wald p-values of the interaction terms of ≤ 0.20 and strata-specific RDs which crossed the null value. Social cohesion, volunteerism, property preparation, church attendance, neighbor's evacuation, and the number of local friends and family modified the RDs for the demographic characteristics.CONCLUSIONS: The associations between demographic characteristics and hurricane evacuation failure are modified by social factors. Effect measure modification on the additive scale may help explain the inconsistency of previously published results and is the appropriate measure for targeted interventions that can increase evacuation among certain groups that are missed when average risks are calculated across the population. [ABSTRACT FROM AUTHOR]

Landfalling tropical cyclones present major hazards for the eastern United States. Hurricane Isabel (September 2003) produced more than $3.3 billion in damages from wind, inland riverine flooding, and storm surge flooding, and resulted in 17 fatalities. Case study analyses of Hurricane Isabel are carried out to investigate multiple hazards from landfalling tropical cyclones. The analyses focus on storm evolution following landfall and center on simulations using the Weather Research and Forecasting Model (WRF). WRF simulations are coupled with the 2D, depth-averaged hydrodynamic Advanced Circulation Model (ADCIRC), to examine storm surge in the Chesapeake Bay. Analyses of heavy rainfall and flooding include an examination of the structure and evolution of extreme rainfall over land. Intercomparisons of simulated rainfall from WRF with Hydro-NEXRAD rainfall fields and observations from rain gauge networks are presented. A particular focus of these analyses is the evolving distribution of rainfall, relative to the center of circulation, as the storm moves over land. Similar analyses are carried out for the wind field of Hurricane Isabel as it moves over the mid-Atlantic region. Outer rainbands, which are not well captured in WRF simulations, played a major role in urban flooding and wind damage, especially for the Baltimore metropolitan region. Wind maxima in outer rainbands may also have played a role in storm surge flooding in the upper Chesapeake Bay. [ABSTRACT FROM AUTHOR]

Important differences in evacuation exist across households. This study describes associations between social factors and evacuation from Hurricane Isabel by residents of North Carolina in 2003. Census blocks in three affected counties were stratified by flood zone and 30 census blocks were selected probability proportionate to population size from each flood zone. Within selected blocks, 7 random interview locations were chosen using a geographic information systems-based site selection tool. Risk differences and 95% confidence intervals for evacuation were calculated. High levels of neighborhood social cohesion, markers of territoriality (e.g., no trespassing signs), membership in church or civic organization, volunteerism, neighbors' evacuation, and longer length of residence were associated with reduced hurricane evacuation. Differential levels of social capital, social cohesion, and related social factors contributed to differential rates of evacuation from Hurricane Isabel. Those who reported closer relationships with neighbors and were active volunteers in the community may be more susceptible to evacuation failure and should receive targeted messages regarding evacuation from officials. [ABSTRACT FROM AUTHOR]

Individual perception of risk has consistently been considered an important determinant of hurricane evacuation in published studies and reviews. Adequate risk assessment is informed by environmental and social cues, as well as evacuation intentions and past disaster experience. This cross-sectional study measured perceived flood risk of 570 residents of three coastal North Carolina counties, compared their perception with actual risk determined by updated flood plain maps, and determined if either was associated with evacuation from Hurricane Isabel in 2003. Census blocks were stratified by flood zone and 30 census blocks were randomly selected from each flood zone. Seven interviews were conducted at random locations within selected blocks. Bivariate and multivariable analyses were conducted to produce crude and adjusted risk differences. Neither the designated flood zone of the parcel where the home was located nor the residents' perceived flood risk was associated with evacuation from Hurricane Isabel in the bivariate analysis. In the multivariable analysis, intention to evacuate and home type were important confounders of the association between actual risk and evacuation. The belief that one is at high risk of property damage or injury is important in evacuation decision making. However, in this study, while coastal residents' perceived risk of flooding was correlated with their actual flood risk, neither was associated with evacuation. These findings provide important opportunities for education and intervention by policymakers and authorities to improve hurricane evacuation rates and raise flood risk awareness. [ABSTRACT FROM AUTHOR]

Abstract: Hurricane Isabel reached the Eastern seaboard of North America on 18 September 2003 causing estimated damage >3 billion US dollars and the death of ∼50 people. Isabel is considered to be one of the most significant tropical cyclones to affect Virginia, since the Chesapeake Potomac Hurricane of 1933 and Hurricane Hazel in 1954. A study of the temporal changes in the benthic fauna pre- and post-hurricane was conducted on an intertidal sandflat within the dynamic barrier island system near Wachapreague, Eastern Virginia. Replicate sediment cores were collected 3 weeks before Isabel made landfall and further samples were collected on 5 occasions over the following 20 months. An immediate effect of Isabel was a doubling in the number of species, a significant increase in invertebrate species diversity (H′) and a rise in opportunistic species and deposit feeders, but a non-significant increase in the total number of organisms. Changes in infauna occurred such that by the end of the study there were significantly increased numbers of species, faunal abundances and community diversity measures, as compared with pre-hurricane samples, suggesting a potentially positive medium-term effect of this hurricane perturbation. The most notable direct effects of the hurricane were on the relative abundances of feeding guilds with a reduction in interface feeders from 87% pre-hurricane to 64% post-hurricane, and an increase in surface deposit feeders from 7% pre-hurricane to 20% post-hurricane. The study highlights potential problems in interpreting post-perturbation data when insufficient pre-perturbation data exist. [Copyright &y& Elsevier]

This is the second of a two-part study of the representation of the planetary boundary layer (PBL) in high-resolution Weather Research and Forecast Model (WRF) simulations of Hurricane Isabel (2003). The Yonsei University (YSU) PBL parameterization and the Mellor–Yamada–Janjić (MYJ) PBL parameterization are evaluated by direct comparison to in situ data obtained by research aircraft. The numerical model, simulation design, details of the PBL schemes, and the representation of the boundary layer in the outer-core were presented in Part I. This part presents a detailed study of the inner-core PBL, including its axisymmetric and asymmetric structures, and comparisons to analyses of dropsonde data from previous studies. Although neither PBL scheme was designed specifically for hurricane conditions, their simulated boundary layers are reasonably good representations of the observed boundary layer. Both schemes reproduce certain unique features of the hurricane boundary layer, such as the separate depths of the well-mixed layer and the inflow layer, and the pronounced wind speed maxima near the top of the inflow layer. Modification of the original YSU and MYJ schemes to have ocean roughness lengths more in agreement with recent studies considerably improves the results of both schemes. Even with these improvements, the MYJ consistently produces larger frictional tendencies in the boundary layer than the YSU scheme, leading to a stronger low-level inflow and a stronger azimuthal wind maximum at the top of the boundary layer. For both schemes, differences in the low-level asymmetries between the simulated and observed wind fields appear to be related to eyewall asymmetries forced by environmental wind shear. The effects of varying horizontal and vertical resolutions are also considered. Increasing the vertical resolution in the PBL results in minor improvements in the inner-core structures. Increasing the horizontal resolution around the eyewall also leads to improved boundary layers, as well as an improvement of the vertical structure of the inner-core wind field. A summary and discussion of the results of both Parts I and II is provided. [ABSTRACT FROM AUTHOR]

In this study, the first of two parts, the planetary boundary layer (PBL) depicted in high-resolution Weather Research and Forecast Model (WRF) simulations of Hurricane Isabel (2003) is studied and evaluated by direct comparisons with in situ data obtained during the Coupled Boundary Layer and Air–Sea Transfer Experiment (CBLAST). In particular, two boundary layer schemes are evaluated: the Yonsei University (YSU) parameterization and the Mellor–Yamada–Janjić (MYJ) parameterization. Investigation of these schemes is useful since they are available for use with WRF, are both widely used, and are based on entirely different methods for simulating the PBL. In this first part, the model domains and initialization are described. For additional realism of the low-level thermodynamic environment, a simple mixed layer ocean model is used to simulate ocean cooling. The YSU and MYJ schemes are discussed, along with some modifications. Standard measures of the accuracy of the hurricane simulations, such as track, maximum surface wind speed, and minimum surface pressure are described for a variety of parameter choices and for the two parameterizations. The effects on track and intensity of increased horizontal and vertical resolutions are also shown. A modification of the original YSU and MYJ schemes to have ocean roughness lengths more in agreement with recent studies considerably improves the results of both schemes. Instantaneous wind maxima on the innermost grid with 1.33-km resolution are shown to be an accurate representation of the simulated 1-min sustained winds. The simulated boundary layers are evaluated by direct comparison of the PBL as simulated and as observed by in situ data from the CBLAST experiment in the “outer core” region of the storm. The two PBL schemes and their modified counterparts reproduce the observed PBL remarkably well. Comparisons are also made to the observed vertical fluxes of momentum, heat, and moisture. In Part II, the detailed comparisons of the intensities and structures of the simulated and observed inner-core boundary layers are presented, and the reasons for the differences are discussed. [ABSTRACT FROM AUTHOR]

This article presents information about historic artifacts that were found to have washed up on the beaches at Cape Lookout National Seashore in North Carolina. Shanna Ramsey of the National Park Service found ceramic jars on the beach in 1994 after a storm had caused erosion and deposition in the area. The staff at the Resource Management facility in the park examined and preserved the jars. Two more similar jars were found in the area in 2003 after Hurricane Isabel passed through. Investigation showed the jars to be of Spanish origin and the contents to be olive pits.

Abstract: Tropical Cyclone Isabel of 2003 generated large storm surge, strong waves, and subsequent river flooding in the York River Estuary, USA during its passage across the Chesapeake Bay region. A 3D model was used to investigate the changes of sediment concentration, sediment flux, and the recovery time of the York River Estuary to its naturally evolved condition without the storm. The results showed that two sediment concentration peaks appeared during the storm event. The first one was induced by the large upstream flow and waves during the storm surge rising period, and the later one was caused by the strong downstream flow during the descent of the storm surge. The advection, which was induced by the barotropic gradient, dominated the sediment flux during the storm event. The sediment fluxes increased by a factor of 100 during the rise and descent of the storm surge. A large amount of sediment that was transported into the estuary and eroded from the seabed during the rising of the storm surge was quickly transported out of the estuary during the descent of the storm surge. Waves played a key role in stirring the seabed and increasing the sediment concentration during the storm. Subsequent high freshwater inflow changed the sediment loading and hydrodynamics in the estuary, and thus, influenced the estuarine turbidity maximum (ETM) dynamics profoundly. The ETM moved downstream with the river flooding initially and returned upstream with the waning of river flooding and the re-establishment of gravitational circulation. The effect of river flooding on sediment concentration varied spatially and depended on the changes of ETM locations and vertical mixing. The model results suggest that a large amount of sediment was transported out of the estuary during the storm event and the subsequent river flooding had a larger impact on recovery time of the estuary. [Copyright &y& Elsevier]

The motion of inertial (i.e., finite-size) particles is analyzed in a three-dimensional unsteady simulation of Hurricane Isabel. As established recently, the long-term dynamics of inertial particles in a fluid is governed by a reduced-order inertial equation, obtained as a small perturbation of passive fluid advection on a globally attracting slow manifold in the phase space of particle motions. Use of the inertial equation enables the visualization of three-dimensional inertial Lagrangian coherent structures (ILCS) on the slow manifold. These ILCS govern the asymptotic behavior of finite-size particles within a hurricane. A comparison of the attracting ILCS with conventional Eulerian fields reveals the Lagrangian footprint of the hurricane eyewall and of a large rainband. By contrast, repelling ILCS within the eye region admit a more complex geometry that cannot be compared directly with Eulerian features. [ABSTRACT FROM AUTHOR]

The article presents a study to improve the capability of hurricane intensity and structure forecasts by radar data assimilation using the landfall data of Hurricane Isabel in the U.S. on September 18, 2003. It says that tropical cyclone (TC) track improves well over the past years, but TC intensity forecasts have been recorded for its errors. This study will prove that the use of land-based Doppler radar observations in a mesoscale numerical weather prediction (NWP) model can improve TC intensity forecasts. An overview of the landfall data of hurricane Isabel is offered, along with the conducted radar observations. Meanwhile, the study finds out that the use of radar data assimilation has a potential for improving hurricane intensity and structure forecasts.

Unprecedented observations of Hurricane Isabel (2003) at category 5 intensity were collected from 12 to 14 September. This study presents a detailed analysis of the inner-core structure, atmospheric boundary layer, sea surface temperature, and outflow layer of a superintense tropical cyclone using high-resolution in situ flight-level, NCAR GPS dropwindsonde, Doppler radar, and satellite measurements. The analysis of the dropwindsonde and in situ data includes a comprehensive discussion of the uncertainties associated with this observational dataset and provides an estimate of the storm-relative axisymmetric inner-core structure using Barnes objective analysis. An assessment of gradient and thermal wind balance in the inner core is also presented. The axisymmetric data composites presented in this study suggest that Isabel built a reservoir of high moist entropy air by sea-to-air latent heat flux inside the low-level eye that was utilized as an additional energy source to nearly maintain its extreme intensity even after crossing the cool wake of Hurricane Fabian. It is argued here that the combined mean and asymmetric eddy flux of high moist entropy air from the low-level eye into the eyewall represents an additional power source or “turbo boost” to the hurricane heat engine. Recent estimates of the ratio of sea-to-air enthalpy and momentum exchange at high wind speeds are used to suggest that Isabel utilized this extra power to exceed the previously assumed intensity upper bound for the given environmental conditions on all three days. This discrepancy between a priori potential intensity theory and observations may be as high as 35 m s-1 on 13 September. [ABSTRACT FROM AUTHOR]

A variational data assimilation method is applied to remotely sensed wind data from Hurricanes Gustav (2002) and Isabel (2003) to produce enhanced marine wind estimates. The variational method utilizes constraints to ensure that an optimum combination of winds is determined, in the sense of minimization of a cost function measuring the misfit between observations and background input field data and constraining nongeophysical features in the spatial derivatives. Constraints are multiplied by weights, which are objectively determined by cross validation. Verification is obtained by comparison with available operational in situ buoy observations and analyses winds. It is shown that the newly constructed midlatitude wind fields represent an improvement relative to background wind field estimates and also relative to Quick Scatterometer–National Centers for Environmental Prediction reanalysis blended winds, and that the new winds have an impact on simulations of waves and upper-ocean currents. [ABSTRACT FROM AUTHOR]

Abstract: Hurricane Isabel made landfall along the North Carolina coast on September 18, 2003 (UTC 17:00) and the storm surge exceeded 2.0m in many areas of the Chesapeake Bay and in the York River estuary. River flooding occurred subsequently, and the peak river discharge reached 317 and 104m3 s−1 in the Pamunkey and Mattaponi rivers, respectively. The York River estuary experienced both storm surge and river flooding during the event and the estuary dynamics changed dramatically. This study investigates the hydrodynamics of the York River estuary in response to the storm surge and high river inflows. A three-dimensional model was used to investigate the changes of estuarine stratification, longitudinal circulation, salt flux mechanisms, and the recovery time required for the estuary to return to its naturally evolved condition without the storm. Results show that the salt flux was mainly caused by advection, which was induced by the barotropic gradient during the storm event. The net salt flux increased by a factor of 30 during the rise of the storm surge. However, the large amount of salt transported into the estuary was quickly transported out of the estuary as the barotropic gradient reversed during the descent of the storm surge. Subsequent high freshwater inflow influenced the estuarine circulation substantially. The estuary changed from a partially mixed estuary to a very stratified estuary for a prolonged period. The model results show that it will take about 4 months for the estuary to recover to its naturally evolved salinity distribution after the impacts of the storm surge and freshwater pulse. [Copyright &y& Elsevier]

We evaluated the impact of Hurricane Isabel on nest loss and reproductive performance of Bald Eagles (Haliaeetus leucocephalus) in the lower Chesapeake Bay. Approximately 40% of Bald Eagle nest trees (n = 527) were damaged and 127 nests were lost during the storm. Nest loss was significantly higher than in years prior to and after the storm. Only 46% of pairs that lost nests attempted to breed the following season, compared to 85% of pairs that did not lose nests. Of the pairs that made breeding attempts, only 69% of pairs that lost nests during the hurricane produced young compared to 83% of pairs that did not lose nests. Average brood size was also reduced for pairs that lost nests. The disparity in reproductive performance between the two groups narrowed in the second breeding season after the storm. Hurricane Isabel had a significant but short- lived impact on the Bald Eagle breeding population in the lower Chesapeake Bay. [ABSTRACT FROM AUTHOR]

Reviews of state public health preparedness improvements have been primarily limited to measuring funds expenditures and achievement of cooperative agreement benchmarks. Such reviews fail to assess states' actual capacity for meeting the challenges they may face during an emergency, as evidenced by activities undertaken during the various phases of a disaster. This article examines North Carolina's public health preparedness and response performance during two hurricanes, Hurricane Floyd in 1999 and Hurricane Isabel in 2003, as well as capacity building activities in the intervening years. North Carolina created new infrastructures, enhanced laboratory capacity, and strengthened communications after Hurricane Floyd. These activities facilitated implementation of functional capabilities through effective centralized communication, command and control incident management, and a rapid needs assessment and medical surveillance during Hurricane Isabel. North Carolina continues to implement these capabilities in public health emergencies. Measuring and implementing functional capabilities during exercises or real events facilitates achievement of preparedness performance standards, goals, and objectives. [ABSTRACT FROM AUTHOR]

This study is an observational analysis of the inner-core structure, sea surface temperature, outflow layer, and atmospheric boundary layer of an intense tropical cyclone whose intensity and structure is consistent with recent numerical and theoretical predictions of superintense storms. The findings suggest new scientific challenges for the current understanding of hurricanes. Unprecedented observations of the category-5 Hurricane Isabel (2003) were collected during 12–14 September. This two-part article reports novel dynamic and thermodynamic aspects of the inner-core structure of Isabel on 13 September that were made possible by analysis of these data. Here, a composite of the axisymmetric structure of the inner core and environment of Isabel is estimated using global positioning system dropwindsondes and in situ aircraft data. In Part II, an extreme wind speed observation on the same day is discussed in the context of this work. The axisymmetric data composite suggests a reservoir of high-entropy air inside the low-level eye and significant penetration of inflowing near-surface air from outside. The analysis suggests that the low-level air penetrating the eye is enhanced thermodynamically by acquiring additional entropy through interaction with the ocean and replaces air mixed out of the eye. The results support the hypothesis that this high-entropy eye air “turboboosts” the hurricane engine upon its injection into the eyewall clouds. Recent estimates of the ratio of sea-to-air enthalpy and momentum exchange at high wind speeds are used to suggest that Isabel utilized this extra power to exceed the previously assumed intensity upper bound by 10–35 m s-1 for the given environmental conditions. Additional study with other datasets is encouraged to further test the superintensity hypothesis. [ABSTRACT FROM AUTHOR]

An unprecedented dataset of category-5 Hurricane Isabel was collected on 12–14 September 2003. This two-part series focuses on novel dynamical and thermodynamical aspects of Isabel's inner-core structure on 13 September. In Part I, using a composite of dropwindsonde and in situ aircraft data, the authors suggested that the axisymmetric structure of Isabel showed that the storm was superintense. Mesocyclones seen clearly in satellite imagery within the eye of Hurricane Isabel are hypothesized to mix high-entropy air at low levels in the eye into the eyewall, stimulating explosive convective development and a concomitant local horizontal wind acceleration. Part II focuses on a unique set of observations into an extraordinary small- (miso) scale cyclonic feature inside of the inner edge of the eyewall of Hurricane Isabel. A dropwindsonde released into this feature measured the strongest known horizontal wind in a tropical cyclone. This particular observation is discussed in the context of concurrent observations from airborne Doppler radar and other airborne instruments. These observations show wind even stronger than the system-scale superintense wind suggested in Part I. Speculation on the frequency of occurrence of these “little whirls” and their potentially catastrophic impacts are presented. [ABSTRACT FROM AUTHOR]

Hurricane Isabel made landfall near Drum Inlet, North Carolina on 18 September 2003. In nearby Onslow Bay an array of 5 moorings captured the response of the coastal ocean to the passage of the storm by measuring currents, surface waves, bottom pressure, temperature and salinity. Temperatures across the continental shelf decreased 5 by 1-3°C, consistent with a surface heat flux estimate of 750 W/m2. Salinity decreased at most mooring locations. A calculation at one of the moorings estimates rainfall of 11 cm and a net addition of fresh water at the surface of 8 cm. The low-pass current field shows a shelf-wide movement of water, first to the southwest, with an abrupt reversal to the northeast along the shelf after landfall. Close analysis of this reversal 10 shows it to be a disturbance propagating offshore at a speed somewhat less than the local shallow water wave speed. The high-pass current field at one of the moorings shows a significant increase in kinetic energy at periods between 10 min and 2 h during the approach of the storm. This high-pass flow is isotropic and has a short (<5 m) vertical decorrelation scale. It appears to be closely associated with the winds, Finally 15 we examined the surface wave field at one of the moorings. It shows the swell energy peaking well before the winds waves. At the height of the storm, as the winds rotated rapidly in the cyclonic sense, the wind wave direction rotated as well, with a lag of 45-90°. [ABSTRACT FROM AUTHOR]

Abstract: Hurricane Isabel made landfall near Drum Inlet, North Carolina on September 18, 2003 (UTC 17:00). Although it was classified as only a Category 2 storm (Saffir–Simpson scale), Hurricane Isabel had a significant impact on the Chesapeake Bay with a 1.5–2.0m storm surge (above mean sea level), and was dubbed the “100-year storm”. A high-resolution unstructured grid model (UnTRIM) was applied to simulate storm tide in the Chesapeake Bay. The application of an unstructured grid in the Bay offers the greatest flexibilities in representing complex estuarine geometry near the coast and encompassing a large modeling domain necessary for storm surge simulation. The resulting mesh has a total of 239,541 surface elements. The model was forced by 9 tidal harmonic constituents at the open boundary and a wind field generated by a parametric wind model. A hindcast simulation of Hurricane Isabel captures both peak storm tide and surge evolution in various sites of the Bay. Model diagnostic studies indicate that the high surge occurring in the upper Bay regions was mainly caused by the forced southerly wind, whereas the offshore surge and both the northeasterly and southeasterly winds influenced the lower Bay region more significantly. [Copyright &y& Elsevier]

This article examines the impact of the swells of Hurricane Isabel on the southeast coast of Florida. The waves generated by the powerful Hurricane Isabel broke along a narrow 10-mile stretch of beaches along southern Palm Beach County on September 16, 2003. Hurricane Isabel's strong winds produced large ocean swells that traveled west-northwest toward the Bahama Islands. Although observation data are lacking in the wave-generation area, these swells were likely made larger as Isabel moved west over a long stretch of ocean in the direction of the strongest winds, producing a longer fetch. The large swells impacted the beaches of Eleuthra and Abaco Islands, shielding most of the southeast Florida coastline.

The accuracy of the operational wave models at the National Centers for Environmental Prediction (NCEP) for sea states generated by Hurricane Isabel is assessed. The western North Atlantic (WNA) and the North Atlantic hurricane (NAH) wave models are validated using analyzed wind fields, and wave observations from the Jason-1 altimeter and from 15 moored buoys. Both models provided excellent guidance for Isabel in the days preceding landfall of the hurricane along the east coast of the United States. However, the NAH model outperforms the WNA model in the initial stages of Isabel, when she was a category 5 hurricane. The NAH model was also more accurate in providing guidance for the swell systems arriving at the U.S. coast well before landfall of Isabel. Although major model deficiencies can be attributed to shortcomings in the driving wind fields, several areas of potential wave model improvement have been identified. [ABSTRACT FROM AUTHOR]

Abstract: Hurricane Isabel made landfall on the southeastern U.S. coast along the lower Outer Banks of North Carolina near Cape Lookout, NC on September 18, 2003. An instrumented quadrapod frame moored approximately 43.5km off the coast of Wilmington, NC in Onslow Bay, at a depth of approximately 30m, was present on the shelf when the hurricane passed approximately 160km from Onslow Bay. The attached instrumentation includes a downward-looking Pulse-Coherent Acoustic Doppler Profiler (PC-ADP) and an upward-looking Acoustic Doppler Current Profiler (ADCP). Simultaneous measurements of flow velocities from the surface to the seabed along with acoustic backscatter measurements and seabed elevation were obtained during this storm event. Three days prior to the direct effects of the hurricane, long-period swells (14–17s) began to impact the area causing sediment transport to occur on the mid-shelf. Shear velocities calculated from a bottom boundary layer model ranged from approximately 6 to 10cms−1 over the course of the sediment transport event. Based on shear velocity calculations, bedload and suspended sediment transport were occurring at the site 72h prior to the passage of the hurricane as long-period swells reached heights of 4m. The seabed altimeter recorded large fluctuations during the storm but was unable to trace elevation changes due to the presence of a highly concentrated layer of suspended sediments in the lower 10cm of the bottom boundary layer. Large amounts of suspended sediment transport occurred in the along-shelf direction towards the southwest after tropical storm force winds of 30ms−1 began to directly affect the area and wind-driven currents were generated. Wind-driven, subtidal currents responded rapidly to local wind forcing and shifted from 15cms−1 towards the southwest to 16cms−1 towards the northeast. Model calculated velocity profiles compared well with measured current velocity profiles. Boxcores collected pre- and post-storm show a storm layer of approximately 5cm and a sediment trap that was attached to the frame 30cm above the bed collected approximately 400cm3 of fine to medium sands that were suspended during the storm. [Copyright &y& Elsevier]

This Letter analyses changes in ocean colour properties caused by hurricane Isabel. Isabel hit the east coast of' the USA on 18 September 2003 causing excessive rainfall and unprecedented flooding. This resulted in drastic changes in land and coastal ocean water bodies. The present study involves the use of Moderate Resolution Imaging Spectroradiometer (MODIS) data for mapping the changes in ocean colour brought by Isabel. Significant increases in the chlorophyll and suspended matter concentrations were found along the entire eastern coastline. Higher rainfall estimated by the Tropical Rainfall Measuring Mission (TRMM) Microwave Imager (TMI) and wind speed estimated by the Quick Scatterometer (QuikSCAT) were found, associated with hurricane Isabel, and are responsible for the changes in ocean colour properties. [ABSTRACT FROM AUTHOR]

In this essay the author narrates her experience of the effects of the Hurricane Isabel. The Hotel Ibis in Caen, France, felt to me like a ship, with its narrow interior hallways, guest room doors high-silled to appear watertight and inspire confidence, the dining room with picture windows on one side. I realized the exact ship I remembered was the ferry on which I had crossed the English Channel from Dover to Zeebrugge, Belgium, in 1977. This was a night crossing, and very rough; thus the windows in the lounge were dark mirrors, reflecting the varied discomforts of the passengers. So it seemed entirely logical that my husband should awaken me with news about water, water where it ought not to be, inside our house, our new house in North Carolina.

The article presents information related to the propagation of Persea Palustris on the aftermath of Hurricane Isabel. Persea palustris is a small evergreen tree with broad, fragrant leaves. It is one of the 3 important bay species. In mid-April, people plant clean, stratified seeds 1.2 cm deep in RootMaker containers. These containers hold 235 ml of a moisture retentive, locally produced, proprietary composted medium. People place containers outdoors on raised beds covered with 30% shade cloth that doubles as an insect barrier. The containers are fertigated with a constant liquid fertilizer as needed to maintain the medium at field capacity.