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Montgomery M.T.,Naval Postgraduate School, Monterey | Montgomery M.T.,Hurricane Research Division | Davis C.,U.S. National Center for Atmospheric Research | Dunkerton T.,NorthWest Research Associates, Inc. | And 14 more authors.
Bulletin of the American Meteorological Society | Year: 2012

The principal hypotheses of a new model of tropical cyclogenesis, known as the marsupial paradigm, were tested in the context of Atlantic tropical disturbances during the National Science Foundation (NSF)-sponsored Pre-Depression Investigation of Cloud Systems in the Tropics (PREDICT) experiment in 2010. PREDICT was part of a tri-agency collaboration, along with the National Aeronautics and Space Administration's Genesis and Rapid Intensification Processes (NASA GRIP) experiment and the National Oceanic and Atmospheric Administration's Intensity Forecasting Experiment (NOAA IFEX), intended to examine both developing and nondeveloping tropical disturbances. During PREDICT, a total of 26 missions were flown with the NSF/NCAR Gulfstream V (GV) aircraft sampling eight tropical disturbances. Among these were four cases (Fiona, ex-Gaston, Karl, and Matthew) for which three or more missions were conducted, many on consecutive days. Because of the scientific focus on the Lagrangian nature of the tropical cyclogenesis process, a wave-relative frame of reference was adopted throughout the experiment in which various model-and satellite-based products were examined to guide aircraft planning and real-time operations. Here, the scientific products and examples of data collected are highlighted for several of the disturbances. The suite of cases observed represents arguably the most comprehensive, self-consistent dataset ever collected on the environment and mesoscale structure of developing and nondeveloping predepression disturbances. © 2012 American Meteorological Society.

Zhu P.,Florida International University | Zhang J.A.,Hurricane Research Division | Masters F.J.,University of Florida
Journal of the Atmospheric Sciences | Year: 2010

Using wavelet transform (WT), this study analyzes the surface wind data collected by the portable wind towers during the landfalls of six hurricanes and one tropical storm in the 2002-04 seasons. The WT, which decomposes a time series onto the scale-time domain, provides a means to investigate the role of turbulent eddies in the vertical transport in the unsteady, inhomogeneous hurricane surface layer. The normalized WT power spectra (NWPS) show that the hurricane boundary layer roll vortices tend to suppress the eddy circulations immediately adjacent to rolls, but they do not appear to have a substantial effect on eddies smaller than 100 m. For low-wind conditions with surface wind speeds less than 10 m s-1, the contributions of small eddies (< 236 m) to the surface wind stress and turbulent kinetic energy (TKE) decrease with the increase of wind speed. The opposite variation trend is found for eddies greater than 236 m. However, for wind speeds greater than 10 m s-1, contributions of both small and large eddies tend to level off as wind speeds keep increasing. It is also found that the scale of the peak NWPS of the surface wind stress is nearly constant with a mean value of approximately 86 m, whereas the scale of the peak NWPS of TKE generally increases with the increase of wind speed, suggesting the different roles of eddies in generating fluxes and TKE. This study illustrates the unique characteristics of the surface layer turbulent structures during hurricane landfalls. It is hoped that the findings of this study could enlighten the development and improvement of turbulent mixing schemes so that the vertical transport processes in the hurricane surface layer can be appropriately parameterized in forecasting models. © 2010 American Meteorological Society.

News Article | September 10, 2016

For those on the East Coast, today would normally be a good day to get those rain boots out, check the emergency food stash and make sure the candles are well-stocked. Sept. 10 is the peak day for hurricane activity along the U.S. Atlantic coast. While none are brewing right now, odds are elevated today, as a result of a confluence of factors, from winds, to atmospheric pressure to ocean water temperature, according to the National Atmospheric and Oceanic Administration. Of course, that doesn't mean a nasty storm is actually in store for the Atlantic coast. (Indeed, the East Coast is experiencing rather ordinary seasonal weather as it recovers from the wrath of last week's Hurricane Hermine.) [Hurricanes from Above: Images of Nature's Biggest Storms] "The tropical activity is usually greatest on average on that day," said Neal Dorst, a researcher with the NOAA Atlantic Oceanographic and Meteorological Laboratory Hurricane Research Division. "But your mileage may vary. From one year to the next, there is no guarantee that there will be a hurricane on Sept. 10, only that it is the most likely on that day." Multiple factors affect the risk of a hurricane forming. For instance, around this time of the year, the subtropical ridge, a belt of high atmospheric pressure that usually sits above the mid-latitudes, has migrated northward. It has migrated far enough north that it allows tropical disturbances, or slight air circulation regions that center around the trade winds, to move across the deep tropical Atlantic Ocean, Dorst told Live Science in an email. At the same time, there is little vertical wind shear, Dorst said. Vertical wind shear, or the change in wind speed with height in the atmosphere, takes the oomph out of a building hurricane by transporting heat and moisture from its center and by tilting its vortex, which makes it less efficient at generating heat, according to Weather Underground. With low shear, there is little to blunt the buildup of heat and moisture needed to fuel a hurricane. The sun's rays have also warmed the deep tropical waters off the Atlantic during this period, while air temperatures rise as well. At the same time, the middle levels of the atmosphere are chock-full of moisture, the perfect fuel for wet, gusty hurricanes, Dorst said. All these factors are likeliest to line up today, according to NOAA's weather models. Tropical storms occur during a narrow, eight-week window between mid-August and late October, according to NOAA. This peak season includes 78 percent of the tropical storm days, 87 percent of Category 1 and 2 hurricanes and a whopping 96 percent of the Category 3, 4 and 5 storms on the Saffir-Simpson scale. By the end of fall, storm chasers can put away their instruments, binoculars and galoshes. Wind shear picks up, breaking up would-be hurricanes before they can form, while ocean water and air temperatures are not conducive to hurricane formation in the first place. "After the peak of the season, these conditions become less favorable for tropical cyclone development until late fall when they become inimical to any storm formation," Dorst said. Copyright 2016 LiveScience, a Purch company. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.

Ming J.,Nanjing University | Zhang J.A.,Hurricane Research Division | Zhang J.A.,University of Miami | Rogers R.F.,Hurricane Research Division
Journal of Geophysical Research D: Atmospheres | Year: 2015

The data from 438 Global Positioning System dropsondes in six typhoons are analyzed to investigate the mean atmospheric boundary layer structure in a composite framework. Following a recent study on boundary layer height in Atlantic hurricanes, we aim to quantify characteristics of boundary layer height scales in Western Pacific typhoons including the inflow layer depth (hinflow), height of the maximum tangential wind speed (hvtmax), and thermodynamic mixed layer depth. In addition, the kinematic and thermodynamic boundary layer structures are compared between the dropsonde composites using data in typhoons and hurricanes. Our results show that similar to the hurricane composite, there is a separation between the kinematic and thermodynamic boundary layer heights in typhoons, with the thermodynamic boundary layer depth being much smaller than hinflow and hvtmax in the typhoon boundary layer. All three boundary layer height scales tend to decrease toward the storm center. Our results confirm that the conceptual model of Zhang et al. (2011a) for boundary layer height variation is applicable to typhoon conditions. The kinematic boundary layer structure is generally similar between the typhoon and hurricane composites, but the typhoon composite shows a deeper inflow layer outside the eyewall than the hurricane composite. The thermodynamic structure of the typhoon boundary layer composite is warmer and moister outside the radius of maximum wind speed than the hurricane composite. This difference is attributed to different environmental conditions associated with typhoons compared to the hurricanes studied here. Key Points There is a separation between kinematic and thermodynamic BL heights in typhoons The BL height scales tend to decrease toward the storm center The BL of typhoon composite is warmer and moist outside the RMW © 2015. American Geophysical Union. All Rights Reserved.

Ming J.,Nanjing University | Zhang J.A.,Hurricane Research Division | Zhang J.A.,University of Miami
Advances in Atmospheric Sciences | Year: 2016

The effects of surface flux parameterizations on tropical cyclone (TC) intensity and structure are investigated using the Advanced Research Weather Research and Forecasting (WRF-ARW) modeling system with high-resolution simulations of Typhoon Morakot (2009). Numerical experiments are designed to simulate Typhoon Morakot (2009) with different formulations of surface exchange coefficients for enthalpy (CK) and momentum (CD) transfers, including those from recent observational studies based on in situ aircraft data collected in Atlantic hurricanes. The results show that the simulated intensity and structure are sensitive to CK and CD, but the simulated track is not. Consistent with previous studies, the simulated storm intensity is found to be more sensitive to the ratio of CK/CD than to CK or CD alone. The pressure–wind relationship is also found to be influenced by the exchange coefficients, consistent with recent numerical studies. This paper emphasizes the importance of CD and CK on TC structure simulations. The results suggest that CD and CK have a large impact on surface wind and flux distributions, boundary layer heights, the warm core, and precipitation. Compared to available observations, the experiment with observed CD and CK generally simulated better intensity and structure than the other experiments, especially over the ocean. The reasons for the structural differences among the experiments with different CD and CK setups are discussed in the context of TC dynamics and thermodynamics. © 2016, Chinese National Committee for International Association of Meteorology and Atmospheric Sciences, Institute of Atmospheric Physics, Science Press and Springer-Verlag Berlin Heidelberg.

Reed D.A.,University of Washington | Powell M.D.,Hurricane Research Division | Westerman J.M.,University of Washington
Natural Hazards Review | Year: 2010

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. © 2010 ASCE.

Ming J.,Nanjing University | Zhang J.A.,University of Miami | Zhang J.A.,Hurricane Research Division | Rogers R.F.,Hurricane Research Division | And 3 more authors.
Journal of Geophysical Research B: Solid Earth | Year: 2014

This paper analyzes data collected from a new set of observational platforms in the coastal area of China, which consist of a mobile observation system, meteorological tower, automatic weather station, and Doppler radars, to investigate the mean and turbulent boundary layer structure and evolution during the landfall of typhoons. An example of these data is provided from Typhoon Morakot (2009). Vertical profiles of wind velocities and thermodynamic parameters from the observed data allow us to identify different boundary layer structures during and after landfall. These structures, sampled in regions of the outer core, are strati fied into periods where convection is occurring (termed "convective") and periods where convection has recently (<2 h) occurred (termed "postconvective"). Data analyses show that the thermodynamic mixed-layer depth and inflow layer depth are higher during the convective period than the postconvective period. The mixed-layer depth is found to be within the strong inflow layer, but the height of the maximum tangential wind speed is above the inflow layer during both periods, contrary to recent observational studies of the boundary-layer structure of tropical cyclones over water. High-frequency wind data show that momentum flux, turbulent kinetic energy (TKE) and integral length scales of wind velocities are all much larger during the convective period than the postconvective period. The results suggest that convective downdrafts may play an important role in modulating turbulent flux, TKE, vertical mixing, and boundary layer recovery processes. ©2014. American Geophysical Union. All Rights Reserved.

Guimond S.R.,Ocean and Atmospheric Science | Guimond S.R.,NASA | Bourassa M.A.,Ocean and Atmospheric Science | Reasor P.D.,Hurricane Research Division
Journal of the Atmospheric Sciences | Year: 2011

Despite the fact that latent heating in cloud systems drives many atmospheric circulations, including tropical cyclones, little is known of its magnitude and structure, largely because of inadequate observations. In this work, a reasonably high-resolution (2 km), four-dimensional airborne Doppler radar retrieval of the latent heat of condensation/evaporation is presented for rapidly intensifying Hurricane Guillermo (1997). Several advancements in the basic retrieval algorithm are shown, including 1) analyzing the scheme within the dynamically consistent framework of a numerical model, 2) identifying algorithm sensitivities through the use of ancillary data sources, and 3) developing a precipitation budget storage term parameterization. The determination of the saturation state is shown to be an important part of the algorithm for updrafts of;5 m s-1 or less. The uncertainties in the magnitude of the retrieved heating are dominated by errors in the vertical velocity. Using a combination of error propagation and Monte Carlo uncertainty techniques, biases are found to be small, and randomly distributed errors in the heating magnitude are;16% for updrafts greater than 5 m s-1 and;156% for updrafts of 1 m s-1. Even though errors in the vertical velocity can lead to large uncertainties in the latent heating field for small updrafts/downdrafts, in an integrated sense the errors are not as drastic. In Part II, the impact of the retrievals is assessed by inserting the heating into realistic numerical simulations at 2-kmresolution and comparing the generated wind structure to the Doppler radar observations of Guillermo. © 2011 American Meteorological Society.

Quirino T.S.,Hurricane Research Division | Delgado J.,University of Miami | Zhang X.,University of Miami
Proceedings - 16th IEEE International Conference on High Performance Computing and Communications, HPCC 2014, 11th IEEE International Conference on Embedded Software and Systems, ICESS 2014 and 6th International Symposium on Cyberspace Safety and Security, CSS 2014 | Year: 2014

The Hurricane Weather Research and Forecasting (HWRF) model is one of the premier models in NOAA's operational suite of severe weather forecasting systems. An axiom in numerical weather prediction suggests that modeling the environment at high resolution optimizes forecast accuracy. However, due to operational time constraints, only the region immediately surrounding a single hurricane can be modeled in high resolution. Currently, this is achieved by embedding a relatively small high resolution, storm-following pair of grids within a larger and coarser grid. In a previous work, we extended HWRF to support multiple such independent storm-following pair of grids. The result was improved forecast accuracy by virtue of modeling storm-to-storm interactions in high resolution. However, some shortcomings in the underlying WRF framework cause these independent pairs of grids to be simulated sequentially. This limits the model's scalability and makes it impossible to harness this novel capability within the operational time constraints. In this paper, we address this issue by modifying the underlying WRF framework to simulate these independent pairs of storm-following grids in parallel. This is the first approach to be successfully implemented in the history of the WRF framework. © 2014 IEEE.

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