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Forecasting tropical cyclones (TCs) with an ensemble of high-resolution regional numerical weather prediction (NWP) models is an ideal test case for new capabilities enabled by cloud computing. Accurately predicting storm [...]

ABSTRACT The hurricane project at the National Oceanic and Atmospheric Administration (NOAA) Geophysical Fluid Dynamics Laboratory (GFDL) was established in 1970. By the mid-1970s pioneering research had led to the [...]

The mean absolute error of the official tropical cyclone (TC) intensity forecasts from the National Hurricane Center (NHC) and the Joint Typhoon Warning Center (JTWC) shows limited evidence of improvement over the past two decades. This result has sometimes erroneously been used to conclude that little or no progress has been made in the TC intensity guidance models. This article documents statistically significant improvements in operational TC intensity guidance over the past 24 years (1989-2012) in four tropical cyclone basins (Atlantic, eastern North Pacific, western North Pacific, and Southern Hemisphere). Errors from the best available model have decreased at l%-2% [yr.sup.-1] at 24-72 h, with faster improvement rates at 96 and 120 h. Although these rates are only about one-third to one-half of the rates of reduction of the track forecast models, most are statistically significant at the 95% level. These error reductions resulted from improvements in statistical-dynamical intensity models and consensus techniques that combine information from statistical-dynamical and dynamical models. The reason that the official NHC and JTWC intensity forecast errors have decreased slower than the guidance errors is because in the first half of the analyzed period, their subjective forecasts were more accurate than any of the available guidance. It is only in the last decade that the objective intensity guidance has become accurate enough to influence the NHC and JTWC forecast errors., Contrary to what is often reported in the literature, tropical cyclone intensity forecast models have improved over the past two decades at a rate that is statistically significant. Tropical cyclone [...]

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

To authenticate to the full-text of this article, please visit this link: http://dx.doi.org/10.1111/j.1475-682X.2010.00345.x Byline: J. Steven Picou (1), Kenneth Hudson (2) Abstract: Katrina was the most devastating and deadliest hurricane in recent U.S. history. The storm was particularly destructive for residents of the Mississippi Gulf Coast where sustained winds of 135 mph and a storm surge of 32 feet literally obliterated the built and modified environments. Limited research exists on the chronic (32 months) mental health impacts of survivors in this geographical area. Random-digit dialing telephone surveys were administered in Harrison and Hancock counties (Mississippi) in April and May 2008 and data were collected on a number of mental health outcomes. The results of the calculation of Oridinary Least Squares (OLS) regression models revealed that females, African Americans, and less-educated residents manifested the most severe mental health impacts. Most important, consistent findings for depression and Katrina-related psychological stress indicate that residents who were separated from family members, had maximum residential damage, and suffered severe financial problems remained significantly impacted 32 months after Katrina's landfall. A secondary stressor, in the form of having applications to the Mississippi State Grant Program denied or not processed also predicted personal depression. The implications of these findings are discussed. Author Affiliation: (1)University of South Alabama (2)University of South Alabama

To authenticate to the full-text of this article, please visit this link: http://dx.doi.org/10.1111/j.1467-8624.2010.01463.x Byline: Ryan P. Kilmer (1), Virginia Gil-Rivas (1) Abstract: This study explored posttraumatic growth (PTG), positive change resulting from struggling with trauma, among 7- to 10-year-olds impacted by Hurricane Katrina. Analyses focused on child self-system functioning and cognitive processes, and the caregiving context, in predicting PTG at 2 time points (Time 1 n = 66, Time 2 n = 51). Findings suggest that rumination, both negative, distressing thoughts and constructive, repetitive thinking, plays an important role in PTG. Hypotheses regarding future expectations and perceived competence were not fully supported, and, unexpectedly, coping competency beliefs, realistic control attributions, and perceived caregiver warmth did not contribute to PTG models. With 1 exception (positive reframing coping advice), caregiver-reported variables did not relate to PTG; no caregiver variable reached significance in final models. Relevant theory, developmental considerations, and future directions are discussed. Author Affiliation: (1)University of North Carolina at Charlotte Article note: Correspondence concerning this article should be addressed to Ryan P. Kilmer, Department of Psychology, The University of North Carolina at Charlotte, 9201 University City Blvd., Charlotte, NC 28223-0001. Electronic mail may be sent to rpkilmer@uncc.edu.

The NOAA Hurricane Research Division (HRD) P-3 aircraft provided airborne radar observations during the period of rapid intensification of Hurricane Guillermo on 2 August 1997. The inner core structure and evolution of Hurricane Guillermo (1997) over a 120 km by 120 km square area, centered on the storm, was observed by the P-3 aircraft during 10 flight legs at half-hour intervals during a 6-h period from 1800 UTC 2 August to 0000 UTC 3 August 1997. A high-resolution short-term model forecast initialized at 1800 UTC 2 August 1997 was made using the fifth-generation Pennsylvania State University-NCAR nonhydrostatic, two-way interactive, movable, triply nested grid Mesoseale Model (MM5). The weak vortex at the initial time in the NCEP analysis was replaced by a tropical storm-like vortex generated by a 4D variational data assimilation (4D-Var) vortex initialization experiment. The modeled Guillermo followed the observed track with less than a 12-kin track error at any time during the 6-h forecast period. The modeled eye is smaller than the observed eye and the modeled vortex is more upright than shown by the radar analysis. The minimum pressure, maximum wind (intensity), and radial profile of tangential winds are close to the radar analysis after 2-3 h of model spinup. A spectral decomposition further reveals that (i) large differences between the model simulation and radar analysis of the asymmetric features are mostly caused by azimuthal phase errors; (ii) the wavenumber 1 component dominates the asymmetric features and remains stationary within the inner core region, as is also observed by airborne Doppler radar; and (iii) although being significantly different from radar analysis, the azimuthal phase of the wavenumber 1 component of modeled reflectivity does not vary greatly with time as the radar data suggest. DOI: 10.1175/2009JAMC2182.1

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

Byline: Paul S. Davies (1), Jeffrey Hemmeter (2) Keywords: Supplemental Security Income (SSI); Katrina; Rita; Hurricane; Administrative data; Natural hazards; Natural disasters; Welfare; Well-being; Environment Abstract: Approximately 350,000 Supplemental Security Income (SSI) recipients--elderly and disabled individuals with low incomes and assets--lived in the areas directly affected by Hurricanes Katrina and Rita in August 2005. We show that recipients from affected areas were more likely to leave the program, have more volatile participation patterns, and leave the area in the 2 years following the hurricanes than were recipients from unaffected areas. Among recipients from more severely affected areas relative to those from unaffected states, the odds of dying were 40% greater and the odds of leaving SSI for other reasons were 23% greater. Additionally, 31% of recipients from more severely affected areas had experienced a non-payment month, with 46% subsequently returning to the rolls (compared with 23% and 41% of recipients from unaffected states). Nearly 60% of SSI recipients from more severely affected areas lived in a different county or parish 2 years after the hurricanes, compared with about 12% from unaffected areas. In all, our findings demonstrate that natural disasters such as Hurricanes Katrina and Rita can have large and persistent impacts on SSI recipients, including effects on program status, mortality, and geographic location. Author Affiliation: (1) Office of Research, Evaluation, and Statistics, Social Security Administration, 500 E Street SW, Room 922, Washington, DC, 20254, USA (2) Office of Program Development and Research, Social Security Administration, 6401 Security Blvd, 3-C-25 Operations, Baltimore, MD, 21235, USA Article History: Registration Date: 24/11/2009 Online Date: 13/12/2009 Article note: The findings and conclusions expressed are solely those of the authors and do not represent the views of the Social Security Administration or any agency of the Federal government.