Download or read book Tropical Cyclone Structure and Intensity Change Related to Eyewall Replacement Cycles and Annular Storm Formation Utilizing Objective Interpretation of Satellite Data and Model Analyses written by James P. Kossin and published by . This book was released on 2009 with total page 8 pages. Available in PDF, EPUB and Kindle. Book excerpt: This project aims toward increasing our understanding of the dynamics of secondary eyewalls in tropical cyclones and our ability to forecast their formation and associated intensity changes. This is being accomplished through a synergistic combination of theoretical, empirical, and numerical modeling approaches. We expect to apply our results to the construction of objective algorithms that will be transitioned to operations to provide forecasters with new tools for improved forecasting of tropical cyclone structure and intensity.

Download or read book Analyzing Tropical Cyclone Structures During Secondary Eyewall Formation Using Aircraft In situ Observations written by Katharine Wunsch and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In the evolution of mature tropical cyclones (TCs), intensity and structural changes canoccur due to a process called an eyewall replacement cycle (ERC). Secondary eyewall formation(SEF) is the initial phase of an ERC, in which a ring of convection forms outside of the preexistingprimary eyewall of the TC. The dynamical mechanisms for SEF remain unclear, but mosthypotheses rely on the early presence of persistent and widespread rainband convection outside ofthe primary eyewall. The evolving rainband convection has both axisymmetric and asymmetricstructures that play a role in SEF processes. This project uses aircraft reconnaissance observationsfrom the FLIGHT+ dataset to examine the evolution of these structures. We create compositesfrom this dataset which includes USAF C-130 and NOAA P-3 aircraft observations of Atlanticbasin TCs from 1999-2015. The axisymmetric structures of TCs undergoing SEF are firstcompared to intensifying TCs that did not experience an ERC. Tangential wind and angularmomentum profiles show a broadening of the outer wind field prior to SEF, whilethermodynamic observations indicate features consistent with strengthening eyewall convection.Next, the ERC TCs are analyzed in quadrants relative to the deep-layer environmental wind shearto examine the evolution of asymmetric kinematic and thermodynamic structures. We utilize anew normalization technique based on the radii of both eyewalls to isolate structures thatsurround the secondary eyewall before and during SEF. We found that the kinematic structures ofthe developing secondary eyewall were most prominent in the storm half left of the wind shearvector. The thermodynamic structures of the secondary eyewall became more axisymmetric overtime during SEF, but those of the primary eyewall became more asymmetric as it began toweaken prior to being fully replaced. Analyzing observations from Hurricane Earl as a case studyillustrates variations in convective coverage that are captured in the composite study.Understanding the structures observed by aircraft reconnaissance and their relation tomechanisms that lead to SEF will improve our ability to predict the resultant changes in TC intensity and structure.

Download or read book Tropical Cyclone Intensity Analysis Using Satellite Data written by Vernon F. Dvorak and published by . This book was released on 1984 with total page 60 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Impacts of Asymmetric Dynamics on Tropical Cyclone Eyewall Replacement Cycles written by Tsz Kin Lai and published by . This book was released on 2021 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: "In mature tropical cyclones (TCs), secondary eyewall formation (SEF) is a frequently observed feature associated with the formation of an outer (secondary) eyewall outside the existing (primary) eyewall. The two eyewalls are separated by a moat region of convective minimum and vorticity minimum. An SEF is often followed by an eyewall replacement cycle (ERC) during which the contracting outer eyewall gradually intensifies while the inner eyewall dissipates. Throughout this period, significant changes in the size and the intensity of the TC usually occur. Therefore, a better understanding of ERC is desired for better TC forecasts. Nevertheless, the mechanisms underlying inner eyewall decay (IED) and outer eyewall intensification (OEI) are not well-understood. It is widely accepted that the cutoff effect associated with the OE makes the main contribution to the IED. However, radar imagery of some double-eyewall TCs showed that the TC vortices became elliptic prior to and during the IED. This kind of elliptic development could result from the dynamic (barotropic) instability across the moat, which is a region of sign reverse of vorticity gradient and satisfies the Rayleigh necessary condition for barotropic instability. Hence, the instability across the moat (known as the type-2 instability) may also make contributions to IED. As the first part of the thesis (Chapter 2), a study of the simulated Hurricane Wilma (2005) is conducted by using a three-dimensional (3D) cloud-resolving full-physics numerical model. It is found that the timing of the onset of the type-2 instability is coincident with the start of the rapid decrease of the low-level IE circulation, indicating that the circulation of the IE is likely weakened by the vorticity mixing associated with the type-2 instability. In the second part of the thesis (Chapter 3), two 3D numerical experiments are performed to further explore the underlying dynamics. The detailed budget analyses of azimuthally averaged absolute angular momentum (AAM) in the moist full-physics experiment clearly show that the eddy radial flux of vorticity associated with the type-2 instability makes significant contributions to the decrease in AAM of the IE and the increase in AAM of the OE. It is also found that the type-2 instability can work with the cutoff effect to accelerate the IED process. Similar patterns of the AAM budget analyses are also obtained from the dry experiment in which all physics parameterisation schemes are switched off. It is thus suggested that the type-2 instability is a fundamental process responsible for the IED and OEI in these two experiments. In the third part of the thesis (Chapter 4), unforced shallow water (SW) experiments further reveal that the intensity changes in the eyewalls through the eddy radial flux of vorticity are intrinsic nonlinear features of the type-2 instability. In addition, a detailed analysis of the most unstable eigenmode of a double-eyewall TC-like vortex shows evidence of substantial divergence of angular momentum flux over the IE and significant convergence of angular momentum flux over the OE. This further demonstrates that the origin of the intensity changes of the eyewalls is the angular momentum transport from the IE to the OE by the eddy processes associated with the type-2 instability. The last part of the thesis (Chapter 5) discusses the long-term effect of the type-2 instability on the eyewall intensity changes during ERCs. A series of forced and unforced SW experiments, which are initialised with different parameters of the vortex and convective heating, show repeated cycles of decay-intensification after the type-2 instability has been excited for a longer time. It is found that the oscillation results from the periodic elongation and contraction of the vortices associated with the long-term nonlinear evolution of the type-2 instability. These results suggest that predicting the eyewall intensity changes during ERCs may be a challenge"--

Download or read book Tropical Cyclone Origin Movement and Intensity Characteristics Based on Data Compositing Techniques written by W. M. Gray and published by . This book was released on 1979 with total page 140 pages. Available in PDF, EPUB and Kindle. Book excerpt: Up-to-date results of recent tropical cyclone research at Colorado State University are presented. Particular attention is paid to new findings which impact on tropical cyclone analysis and forecasting efforts. Observational studies using large amounts of composited rawinsonde, satellite, and aircraft flight data have been performed to analyze global aspects of tropical cyclone occurrences, physical processes of tropical cyclone genesis, tropical cyclone intensity change, environmental factors influencing tropical cyclone turning motion 24-36 hours before the turn takes place, tropical cyclone intensity determination from upper tropospheric reconnaissance, and the diurnal variations of vertical motion in tropical weather systems. (Author).

Download or read book Satellite Climatology of Tropical Cyclone with Concentric Eyewalls written by Yi-Ting Yang and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: An objective method is developed to identify concentric eyewalls (CEs) for tropical cyclones (TCs) using passive microwave satellite imagery from 1997 to 2014 in the western North Pacific (WNP) and Atlantic (ATL) basin. There are 91 (33) TCs and 113 (50) cases with CE identified in the WNP (ATL). Three CE structural change types are classified as follows: a CE with the inner eyewall dissipated in an eyewall replacement cycle (ERC, 51 and 56% in the WNP and ATL), a CE with the outer eyewall dissipated first and the no eyewall replacement cycle (NRC, 27 and 29% in the WNP and ATL), and a CE structure that is maintained for an extended period (CEM, 23 and 15% in the WNP and ATL). The moat size and outer eyewall width in the WNP (ATL) basin are approximately 20-50% (15-25%) larger in the CEM cases than that in the ERC and NRC cases. Our analysis suggests that the ERC cases are more likely dominated by the internal dynamics, whereas the NRC cases are heavily influenced by the environment condition, and both the internal and environmental conditions are important in the CEM cases. A good correlation of the annual CE TC number and the Oceanic Niño index is found (0.77) in WNP basin, with most of the CE TCs occurring in the warm episodes. In contrast, the El Niño/Southern Oscillation (ENSO) may not influence on the CE formation in the ATL basin. After the CE formation, however, the unfavorable environment that is created by ENSO may reduce the TC intensity quickly during warm episode. The variabilities of structural changes in the WNP basin are larger than that in the ATL basin.

Download or read book Objective Measures of Tropical Cyclone Intensity and Formation from Satellite Infrared Imagery written by and published by . This book was released on 2009 with total page 248 pages. Available in PDF, EPUB and Kindle. Book excerpt: This document proposes an objective technique to estimate the intensity and predict the formation of tropical cyclones using infrared satellite imagery. As the tropical cyclone develops from an unstructured cloud cluster and intensifies the cloud structures become more axisymmetric around an identified reference point or center. This methodology processes the image gradient to measure the level of symmetry of cloud structures, which characterizes the degree of cloud organization of the tropical cyclone. The center of a cloud system is calculated by projecting and accumulating parallel lines to the gradient vectors. The point where the highest number of line intersections is located pinpoints a common point where the corresponding gradients are directed. This location is used as the center of the system. Next, a procedure that characterizes the departure of the weather system structure from axisymmetry is implemented. The deviation angle of each gradient vector relative to a radial line projected from the center is calculated. The variance of the set of deviation angles enclosed by a circular area around the center describes the axisymmetry of the system, and its behavior through time depicts its dynamics. Results are presented that show the time series of the deviation angle variances is well correlated with the National Hurricane Center best-track estimates. The formation of tropical cyclones is detected by extending the deviation-angle variance technique, it is calculated using every pixel in the scene as the center of the cloud system. Low angle variances indicate structures with high levels of axisimmetry, and these values are compared to a set of thresholds to determine whether a cloud structure can be considered as a vortex. The first detection in a sequence indicates a nascent storm. It was found that 86% of the tropical cyclones during 2004 and 2005 were detected 27 h on average before the National Hurricane Center classified them as tropical storms (33kt). Finally, two procedures to locate the center of a tropical cyclone are compared to the National Hurricane Center best-track center database. Results show that both techniques provide similar accuracy, which increases as the tropical cyclone evolves.

Download or read book Environmental and Internal Controls of Tropical Cyclones Intensity Change written by Melicie Desflots and published by . This book was released on 2007 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Tropical cyclone (TC) intensity change is governed by internal dynamics (e.g. eyewall contraction, eyewall replacement cycles, interactions of the inner-core with the rainbands) and environmental conditions (e.g. vertical wind shear, moisture distribution, and surface properties). This study aims to gain a better understanding of the physical mechanisms responsible for TC intensity changes with a particular focus to those related to the vertical wind shear and surface properties by using high resolution, full physics numerical simulations. First, the effects of the vertical wind shear on a rapidly intensifying storm and its subsequent weakening are examined. Second, a fully coupled atmosphere-wave-ocean model with a sea spray parameterization is used to study the impact of sea spray on the hurricane boundary layer. The coupled model consists of three components: the high resolution, non-hydrostatic, fifth generation Pennsylvania State University-NCAR mesoscale model (MM5), the NOAA/NCEPWAVEWATCH III (WW3) ocean surface wave model, and theWHOI threedimensional upper ocean circulation model (3DPWP). Sea spray parameterizations were developed at NOAA/ESRL and modified by the author to be introduced in uncoupled and coupled simulations. The model simulations are conducted in both uncoupled and coupled modes to isolate various physical processes influencing TC intensity. The very high-resolutionMM5 simulation of Hurricane Lili (at 0.5 km grid resolution) showed a rapid intensification associated with a contracting eyewall. Changes in both the magnitude and the direction of the vertical wind shear associated with an approaching upper-tropospheric trough were responsible for the weakening of the storm before landfall. Hurricane Lili weakened in a 5-10 m/s vertical wind shear environment. The simulated storm experienced wind shear direction normal to the storm motion, which produced a strong wavenumber one rainfall asymmetry in the downshear-left quadrant of the storm. The rainfall asymmetry was confirmed by various observations from the TRMM satellite and the WSR-88D ground radar in the coastal region. The increasing vertical wind shear induced a vertical tilt of the vortex with a time lag of about 5-6 hours after the wavenumber one rainfall asymmetry was first observed in the model simulation. Other key factors controlling intensity and intensity change in tropical cyclones are the air-sea fluxes. Accurate measurement and parameterization of air-sea fluxes under hurricane conditions are challenging. Although recent studies have shown that the momentum exchange coefficient levels off at high wind speed, little is known about the high wind behavior of the exchange coefficient for enthalpy flux. One of the largest uncertainties is the potential impact of sea spray. The current sea spray parameterizations are closely tied to wind speed and tend to overestimate the mediated heat fluxes by sea spray in the hurricane boundary layer. The sea spray generation depends not only on the wind speed but also on the variable wave state. A new spray parameterization based on the surface wave energy dissipation is introduced in the coupled model. In the coupled simulations, the wave energy dissipation is used to quantify the amount of wave breaking related to the generation of sea spray. The spray parameterization coupled to the waves may be an improvement compared to sea spray parameterizations that depends on wind speed only.

Download or read book Detecting Tropical Cyclone Secondary Eyewalls with a Microwave Based Scheme written by Alex Cheung and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Intense tropical cyclones (TCs) often form secondary eyewalls, triggering a process known as an eyewall replacement cycle (ERC). This can lead to short-term fluctuations in intensity and an increase in the size of the TC wind field. When occurring near landfall, the short-term variations can dramatically alter coastal watch, warning, and storm surge forecasts, potentially altering pre-storm preparation plans, including evacuations. However, documenting these events can be a time-consuming, subjective, and sometimes difficult task. Here, we use 89 --92 GHz microwave imagery from the NOAA Cooperative Institute for Research in the Atmosphere's Tropical Cyclone PRecipitation, Infrared, Microwave, and Environmental Dataset (TC PRIMED) to develop image-based variables to identify concentric structures related to deep convection. The image-based variables are combined with various environmental and storm variables (e.g, deep-layer shear magnitude, current maximum wind speed, 24-h difference in radius of 5 kt (1 kt = 0.514 m s--1) winds, and 24-h difference in infrared brightness temperature), to create a probabilistic secondary eyewall classification scheme using a machine learning classifier (linear discriminant analysis). This classification scheme is trained and tested using subjectively created secondary eyewall labels (2016--2019) of storms from the North Atlantic, East Pacific, West Pacific, and Southern Hemisphere basins. We trained the classifier using 36 storms and retained 16 storms for testing. From the classifier output, we calculate the probability of detection, false alarm ratios, skill scores, and bias ratio for various probability thresholds. Using the best default probability threshold (50%), the model produced a secondary eyewall probability of detection of about 64% with a false alarm ratio of 34% and a Peirce's Skill Score of 0.52, indicating fair skill in the model.

Download or read book Convectively generated Potential Vorticity in Rainbands and Secondary Eyewall Formation in Hurricanes written by Falko Judt and published by . This book was released on 2009 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Concentric eyewall formation and eyewall replacement cycles are intrinsic processes that determine the intensity of a tropical cyclone, as opposed to purely environmental factors such as wind shear or the ocean heat content. Although extensive research has been done in this area, there is not a single widely accepted theory on the formation of secondary eyewall structures. Many previous studies focused on dynamic processes in the inner core of a tropical cyclone that would precede and ultimately lead to the formation of a secondary eyewall. Hurricanes Katrina and Rita in 2005 were frequently sampled by research aircraft which gathered a copious amount of data. During this time, Rita developed a secondary eyewall which eventually replaced the original eyewall. This thesis will investigate the formation of a secondary eyewall with particular emphasis on the rainband region, as observations show that an outer principal rainband transformed into the secondary ring. A high resolution, full physics model (MM5) initialized with global model forecast fields correctly predicted the secondary eyewall formation in Rita. The model output will be used to investigate both Katrina and Rita in terms of their PV generation characteristics since PV and vorticity maxima correlate well with wind maxima that accompany the eyewall and rainbands. Furthermore, dynamical processes such as vortex Rossby wave (VRW) activity in the inner core region will be analyzed. Comparison of the differences in the two storms might shed some light on dynamics that can lead to structure changes. Comparison of the model data with aircraft observation is used to validate the results. Doppler radar derived wind fields will be used to calculate the vertical vorticity. The vorticity field is closely related to PV and thus a manifestation of the PV generation process in the rainband. The investigation has shown that Rita2s principal rainband features higher PV generation rates at radii beyond 80 km. Both the azimuthal component and the projection of asymmetric PV generated by convection onto the azimuthal mean connected with the principal band are hypothesized to be of importance for the formation of the secondary eyewall. VRW were found not to be important for the initial formation of the ring but might enhance convective activity once the outer eyewall contracts.

Download or read book Tropical cyclone intensity and structure changes Theories observations numerical modeling and forecasting written by Eric Hendricks and published by Frontiers Media SA. This book was released on 2023-09-29 with total page 260 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Current Topics in Tropical Cyclone Research written by Anthony Lupo and published by BoD – Books on Demand. This book was released on 2020-11-04 with total page 160 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book highlights some of the most recent research in the climatological behavior of tropical cyclones as well as the dynamics, predictability, and character of these storms as derived using remote sensing techniques. Also included in this book is a review of the interaction between tropical cyclones and coastal ocean dynamics in the Northwest Pacific and an evaluation of the performance of CMIP6 models in replicating the current climate using accumulated cyclone energy. The latter demonstrates how the climate may change in the future. This book can be a useful resource for those studying the character of these storms, especially those with the goal of anticipating their future occurrence in both the short and climatological range and their associated hazards.

Download or read book Aspects of Moat Formation in Tropical Cyclone Eyewall Replacement Cycles written by Christopher Michael Rozoff and published by . This book was released on 2007 with total page 330 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Effects of Environmental Water Vapor on Tropical Cyclone Structure and Intensity written by Derek Ortt and published by . This book was released on 2007 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Water vapor not only affects TC intensity. Prior modeling studies have demonstrated impacts from environmental water vapor on TC structure. These impacts can also affect intensity change. Specifically, enhanced water vapor content within the TC enhances the rainbands, which can lead to an eyewall replacement cycle, causing a temporary weakening, followed by re-intensification. This thesis evaluates observational and high resolution MM5 model output from Hurricanes Katrina and Rita from the Hurricane Rainband and Intensity Experiment (RAINEX) to evaluate the effects of varying water vapor distributions on TC structure. While the two hurricanes were of similar intensity, they had different water vapor distributions and structures. Rita underwent an eyewall replacement cycle while under RAINEX surveillance while Katrina did not. Rita was also located within a dry environment and had a strong horizontal moisture gradient, while Katrina was in a moist environment and had a weak moisture gradient. Results suggest that a strong horizontal water vapor gradient, with a moist TC and dry outer environment may confine the hurricanes into a pattern that causes them to have high circularity, promoting the formation of a secondary eyewall. The dry outer environment had strong atmospheric stability and was less favorable for deep convection far from the center in the Rita case. The moist environment in the Katrina case was more unstable. This may have allowed for the rainbands to be farther from the center in a less circular pattern than Rita. The results presented in this thesis suggest that this pattern is less favorable for an eyewall replacement cycle.

Download or read book An Experiment in Statistical Prediction of Tropical Cyclone Intensity Change written by Robert T. Merrill and published by . This book was released on 1987 with total page 44 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book The Environments And Associated Physical Mechanisms That Cause Size And Structure Changes In A Tropical Cyclone written by Diana Rose Stovern and published by . This book was released on 2014 with total page 146 pages. Available in PDF, EPUB and Kindle. Book excerpt: Tropical cyclones (TCs) can make significant size changes during their lifetime. Being able to accurately forecast TC size change is important for predicting the onset of storm surge as well as the spatial extent of damaging winds. TC size changes can occur from internal storm dynamics, such as eyewall replacement cycle or from changes in the synoptic environment. In this study, the impacts of changing the atmospheric temperature and air-sea temperature difference on TC size and structure are investigated. The study is conducted in two parts: the first part uses the WRF-ARW model to test the sensitivity of TC size changes to simple changes in the environment; the second part to validates the results from the first part by characterizing the environments associated with real cases of TC size change in the North Atlantic basin. It is found that when the simulated atmosphere is cooled, the initial specific humidity and convective available potential energy (CAPE) decrease but the surface energy fluxes from the ocean increase. The higher surface fluxes produce a wider area of radially-inflowing air in the boundary layer, which supports a larger precipitation field and the formation of outer-core spiral rainbands. The larger precipitation field translates to a larger wind field, which is likely related to the diabatic production of potential vorticity. In contrast, when the atmosphere is warmed the surface energy fluxes reduce, which ultimately inhibits the growth of the TC wind field. The higher initial CAPE and moisture content, however, allow the TC to spin up more rapidly with a compact core of intense precipitation. Thus, it is not the temperature of the atmosphere that is causing the size changes, but instead it is the higher surface energy fluxes that arise from the increased air-sea temperature difference. Diagnostics show that fluxes of angular momentum from the environment are not responsible for the simulated TC size increases, even when the gradient in Earth vorticity is included. Rather, it is the production of energy due to the fluxes from the ocean that is responsible for the TC size increases in these simulations. Finally, a larger TC will increase in size more than a smaller TC in the same environment. In the second part of the study, the environments associated with real cases of TC size change in the North Atlantic Basin were characterized. Size changes were evaluated using the Tropical Cyclone Extended Best Track Dataset, and the environments associated with these size changes were examined using the 6-hourly, ERA-Interim global reanalysis dataset. Environmental composites show that the TCs that made size changes in the deep tropics were typically associated with more environmental, mid-level humidity and higher air-sea temperature difference. The TCs that made large size changes in the extratropics were associated with highly-baroclinic environments and high mid-level moisture south of the TC-circulation center. In general, the environments that were associated with TC size increases in the North Atlantic showed similar characteristics to the size change environments simulated in the first part of this study. In addition, the presence of high, mid-level moisture in both the deep tropics and extratropics was consistent with the results of other modeling studies that have explored the impact of environmental moisture on TC size changes.

Download or read book Diagnosis of Tropical Cyclone Structure and Intensity Change written by and published by . This book was released on 1999 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The long term goals of this project are to improve and refine understanding of the dynamics of tropical cyclone structure and intensity change, with emphasis on the role of environmental dynamical effects on the intensity change process. This project builds upon the experience of the principal investigator in the study of extratropical cyclone dynamics in maritime regions during the past decade, and the recognition that extratropical maritime cyclones bear similarities to their tropical counterparts. Accordingly, a guiding theme of this research effort is to apply and extend well established dynamical perspectives on extratropical maritime cyclogenesis and cyclone life cycles to the tropics. The long term goals of this project have been addressed through diagnostic and modeling investigations of: (1) the origin and evolution of tropopause based precursor disturbances that culminate in rapid maritime cyclogenesis over the western North Atlantic Ocean; (2) the roles of trough interactions in tropical cyclone intensity change with a view toward determining the factors that distinguish between cyclogenetic and cyclolytic trough interactions; (3) the roles of environmental dynamical effects in tropical cyclone structure and intensity change; and (4) the kinematics of vorticity asymmetries associated with nondivergent barotropic vortices on a beta plane.