the governing dynamics of the secondary eyewall formation of typhoon sinlaku 2008 abstractthrough successful convection permitting simulations of typhoon sinlaku 2008 using a high resolution nonhydrostatic model this study examines the role of peripheral convection in the storm s secondary eyewall formation sef and its eyewall replacement cycle erc the study demonstrates that before sef the simulated storm intensifies via an expansion of the tangential winds and an increase in the boundary layer inflow which are accompanied by peripheral convective cells outside the primary eyewall these convective cells which initially formed in the outer rainbands under favorable environmental conditions and move in an inward spiral play a crucial role in the formation of the secondary eyewall it is hypothesized that sef and erc ultimately arise from the convective heating released from the inward moving rainbands the balanced response in the transverse circulation and the unbalanced dynamics in the atmospheric boundary layer along with the positive feedback between these processes

multiscale interactions in the life cycle of a tropical cyclone simulated in a global cloud system resolving model part ii system scale and mesoscale processes abstract the life cycle of tropical storm isobel was simulated reasonably well in the nonhydrostatic icosahedral atmospheric model nicam a global cloud system resolving model the evolution of the large scale circulation and the storm scale structure change was discussed in part i both the mesoscale and system scale processes in the life cycle of the simulated isobel are documented in this paper in the preconditioned favorable environment over the java sea mesoscale convective vortices model mcvs developed in the mesoscale convective systems mcss and convective towers with cyclonic potential vorticity pv anomalies throughout the troposphere model vortical hot towers vhts appeared in the model mcvs multiple model vhts strengthened cyclonic pv in the interior of the model mcv and led to the formation of an upright monolithic pv core at the center of the concentric mcv primary vortex enhancement as the monolithic pv core with a warm core developed near the circulation center the intensif

latest jurassic early cretaceous events and the late cimmerian unconformity in north sea area each of several regional or local unconformities may have been identified locally as the late cimmerian unconformity a supposed major break at the base of the valhall formation or roedby formation over most of the north sea the base of the valhall formation is isochronous and conformable with underlying sediments it is detected on seismic reflection profiles because it represents a widespread facies change marking the late ryazanian transgression most of the unconformities are of eustatic origin and the effects of eustatic sea level changes were never completely masked by local tectonics thus in the modeling of individual oil fields the possibility of sedimentary breaks occurring can be predicted in part by reference to regional or eustatic events modified journal abstract

the multiple vortex nature of tropical cyclogenesis abstract this study explores the extent to which potential vorticity pv generation and superposition were relevant on a variety of scales during the genesis of tropical storm allison allison formed close to shore and the combination of continuous doppler radar satellite aircraft and surface observations allows for the examination of tropical cyclogenesis in great detail preceding allison s genesis pv superposition on the large scale created an environment where decreased vertical shear and increased instability surface fluxes and low level cyclonic vorticity coexisted this presented a favorable environment for meso scale pv production by widespread convection and led to the formation of surface based meso scale vortices termed convective burst vortices cbvs the cbvs seemed to form in association with intense bursts of convection and rotated around each other within the meso circulation field one cbv eventually superposed with a mesoscale convective vortex mcv resulting in a mor

structure of the eye and eyewall of hurricane hugo 1989 on 15 september 1989 one of noaa s wp 3d research aircraft n42rf lower aircraft la penetrated the eyewall of hurricane hugo the aircraft had an engine fail in severe turbulence while passing the radius of maximum wind and before entering the eye at 450 m altitude after the aircraft returned to controlled flight within the 7 km radius eye it gained altitude gradually as it orbited in the eye observations taken during this period provide an updated model of the inner core structure of an intense hurricane and suggest that la penetrated an intense cyclonic vorticity maximum adjacent to the strongest convection in the eyewall eyewall vorticity maximum evm this evm was distinct from the vortex scale cyclonic circulation observed to orbit within the eye three times during the 1 h that la circled in the eye at the time hugo had been deepening rapidly for 12 h the maximum flight level tangential wind was 89 m s 1 at a radius of 12 5 km however the primary vortex peak tangential wind derived from a 100 s filter of the flight level data was estimated to be 70 m s 1 also at 12 5 km radius the primary vortex tangential wind was in approximate gradient wind balance was characterized by a peak in angular velocity just inside the radius of maximum wind and had an annular vorticity structure slightly interior to the angular velocity maximum the evm along the aircraft s track was roughly 1 km in diameter with a peak cyclonic vorticity of 1 25 10 1 s 1 the larger circulation center with a diameter 15 km was observed within the eye and exhibited an average orbital period of 19 min this period is about the same as that of the angular velocity maximum of the axisymmetric mean vortex and is in reasonable agreement with recent theoretical and model predictions of a persistent trochoidal wobble of circulation centers in mature hurricane like vortices this study is the first with in situ documentation of these vortical entities which were recently hypothesized to be elements of a lower tropospheric eye eyewall mixing mechanism that supports strong storms

effects of vertical shears and midlevel dry air on tropical cyclone developments abstracta set of idealized experiments using the weather research and forecasting model wrf were designed to investigate the impacts of a midlevel dry air layer vertical shear and their combined effects on tropical cyclone tc development compared with previous studies that focused on the relative radial position of dry air with no mean flow it is found that the combined effect of dry air and environmental vertical shear can greatly affect tc development moreover this study indicates the importance of dry air and vertical shear orientations in determining the impact the background vertical shear causes the tilting of an initially vertically aligned vortex the shear forces a secondary circulation fsc with ascent descent in the downshear upshear flank hence convection tends to be favored on the downshear side the fsc reinforced by the convection may overcome the shear induced drifting and restore the vertical alignment when dry air is located in the downshear right quadrant of the ini

the role of vortical hot towers in the formation of tropical cyclone diana 1984 abstract a high resolution 3 km horizontal grid spacing near cloud resolving numerical simulation of the formation of hurricane diana 1984 is used to examine the contribution of deep convective processes to tropical cyclone formation this study is focused on the 3 km horizontal grid spacing simulation because this simulation was previously found to furnish an accurate forecast of the later stages of the observed storm life cycle the numerical simulation reveals the presence of vortical hot towers or cores of deep cumulonimbus convection possessing strong vertical vorticity that arise from buoyancy induced stretching of local absolute vertical vorticity in a vorticity rich prehurricane environment at near cloud resolving scales these vortical hot towers are the preferred mode of convection they are demonstrated to be the most important influence to the formation of the tropical storm via a two stage evolutionary process i preconditioning of the local environment via diabatic production of mul

a numerical study of the genesis of extratropical convective mesovortices part i evolution and dynamics abstract the purpose of this study is to understand the genesis of extratropical convective mesovortices and the large scale environmental features that influence the vortex formation a hypothesis is proposed that mesovortices form in the stratiform rain regions of mesoscale convective systems mcss due to the reduction of static stability that reduces the effective local rossby radius in such regions a conceptual model of the mesoscale convective cyclogenesis is introduced which describes the three stages of the mesovortex formation a modified version of the pennsylvania state university national center for atmospheric research three dimensional hydrostatic mesoscale model is used to simulate mesovortex genesis in analytically generated pre mcs large scale environments the model simultaneously incorporates parameterized convection and a grid resolvable convective scheme containing the effects of hydrostatic water loading condensation evaporation freezing melting and sublimation a control si

role of cumulus congestus in tropical cyclone formation in a high resolution numerical model simulation abstractthe role of cumulus congestus shallow and congestus convection in tropical cyclone tc formation is examined in a high resolution simulation of tropical cyclone fay 2008 it is found that cumulus congestus plays a dominant role in moistening the lower to middle troposphere and spinning up the near surface circulation prior to genesis while deep convection plays a key role in moistening the upper troposphere and intensifying the cyclonic circulation over a deep layer the transition from the tropical wave stage to the tc stage is marked by a substantial increase in net condensation and potential vorticity generation by deep convection in the inner wave pouch region this study suggests that tc formation can be regarded as a two stage process the first stage is a gradual process of moisture preconditioning and low level spinup in which cumulus congestus plays a dominant role the second stage commences with the rapid development of deep convection in the inner pouch region after the air colum

back arc rifting in the korea plateau in the east sea japan sea and the separation of the southwestern japan arc from the korean margin abstract the south korea plateau is a remnant of continental crust in the middle of the eastern korean margin that was deformed by extension in association with back arc rifting and separation of the southwestern japan arc in the cenozoic multichannel seismic profiles show that the south korea plateau preserves structure of rift basins flanked by uplifted footwall blocks rift basins in the plateau are filled with distinct syn and post rift sequences separated by a prominent breakup unconformity resulting from uplift the crustal and upper mantle structures computed by ambient noise tomography indicate that the south korea plateau defines the seaward limit of rifted continental crust in addition rifting occurred with vigorous asthenospheric upwelling induced along the korean margin and depth dependent stretching therefore the south korea plateau underwent the entire sequence of tectonic events typical of a passive continental margin encompassing rifting with subsidence uplift erosion and breakup prior to the separation of the southwestern japan arc breakup at the korean margin may substantiate successive episodes of back arc spreading which migrated toward the arc in response to trench retreat we suggest that the southwestern japan arc moved to its present location from the southern part of the korean margin with a significant amount of clockwise rotation during back arc spreading

appraisal of recent theories to understand cyclogenesis pathways of tropical cyclone madi 2013 the present study aims to examine the new understanding of cyclogenesis by analyzing the genesis sequence of formation of a very severe cyclonic storm madi 6 13 december 2013 that occurred over the bay of bengal we have generated a high resolution 18 km 6 km and 2 km analysis using three dimensional variational data assimilation technique and weather research and forecasting model the genesis sequence of madi cyclone is analyzed using the concepts in the marsupial theory and other theories of tropical cyclone formation major results are as follows the developed analysis is found useful for tracking the movement of westward moving parent disturbance from 15 days prior to the genesis identifying developed pouch region in the lagrangian frame of reference understanding the evolution of the pouch and convection within the pouch region and for the study of intensification inside the pouch region also large scale priming of environment concurs with the hypotheses of the marsupial theory of tropical cyclogenesis the analysis of dynamical and thermodynamical processes within the pouch region showed gradual moistening uplifting of moisture diabatic heating causing buoyant convection in the vorticity rich environment followed by vortex tube stretching development of convection heavy precipitation strengthening of lower level convergence and hence spin up during a day or two preceding the genesis of madi cyclone in general it is concluded that intensification within pouch region during the cyclogenesis phase followed the marsupial paradigm and bottom up mechanism

shear forced vertical circulations in tropical cyclones 1 the forced secondary circulation fsc by the vertical shear of horizontal winds is isolated from the latent heating and friction fscs associated with a model simulated hurricane vortex this is achieved by use of a newly developed potential vorticity inversion and quasi balanced vertical motion equations system results show that latent heating forces intense updrafts in the eyewall and slow subsidence in the eye whereas the friction fsc is similar to that of the ekman pumping with the peak ascent occurring near the top of the boundary layer in the eye in contrast when an environmental westerly shear is superposed with an axisymmetric balanced vortex an anticlockwise fsc appears across the inner core region with the rising motion downshear and easterly sheared horizontal flows in the vertical the resulting horizontal flows act to reduce the influence of the vertical shear inside the storm by as much as 30 40 thus opposing the destructive roles of the vertical shear

the formation of moist vortices and tropical cyclones in idealized simulations abstractthe upscale aggregation of convection is used to understand the emergence of rotating coherent midtropospheric structures and the subsequent process of tropical cyclone formation the cloud model version 1 cm1 is integrated on an f plane with uniform sea surface temperature sst and prescribed uniform background flow deep convection is maintained by surface fluxes from an ocean with uniform surface temperature convection begins to organize simultaneously into moist and dry midtropospheric patches after 10 days after 20 days the patches begin to rotate on relatively small scales moist cyclonic vortices merge eventually forming a single dominant vortex that subsequently forms a tropical cyclone on a realistic time scale of about 5 days radiation that interacts with clouds and water vapor aids in forming coherent rotating structures using the path to genesis provided by the aggregated solution the relationship between thermodynamic changes within the vortex and changes in the character

convective contribution to the genesis of hurricane ophelia 2005 abstract the convection occurring in the tropical depression that became hurricane ophelia 2005 was investigated just prior to tropical storm formation doppler radar showed a deep wide intense convective cell of a type that has been previously thought to occur in intensifying tropical depressions but has not heretofore been documented in detail the updraft of the cell was 10 km wide 17 km deep had updrafts of 10 20 m s 1 throughout its mid to upper levels and contained a cyclonic vorticity maximum the massive convective updraft was maintained by strong positive buoyancy which was maximum at about the 10 km level probably aided by latent heat of freezing evaporative cooling and precipitation drag occurred in the rain shower of the cell but were insufficient to produce a strong downdraft or gust front outflow to force the updraft the convective updraft was fed by a layer of strong inflow that was several kilometers deep wind induced turbulence just above the ocean surface enriched the equi

axisymmetric balance dynamics of tropical cyclone intensification and its breakdown revisited abstractthis paper revisits the evolution of an idealized tropical cyclone like vortex forced by a prescribed distribution of diabatic heating in the context of both inviscid and frictional axisymm

development and nondevelopment of binary mesoscale vortices into tropical cyclones in idealized numerical experiments abstractthe evolution of two symmetric midlevel mesoscale vortices situated above a warm ocean is examined with a basic cloud resolving model idealized numerical experiments provide insight into how the evolution may vary with the initial vortex separation distance d and other parameters that influence the time scale for an isolated vortex to begin rapid intensification the latter parameters include the ambient middle tropospheric relative humidity rh and the initial midlevel wind speed of each vortex at relatively low rh there exists an interval of d where binary midlevel vortex interaction prevents tropical cyclone formation while tropical cyclones generally develop at high rh similar values of d can delay the process if the vortices are initially weak prevention or inhibition of tropical cyclone formation occurs in association with the outward expulsion of lower tropospheric potential vorticity anomalies as the two vortices merge in the middle troposphere it is proposed that the primary mecha

on the creation and evolution of small scale low level vorticity anomalies during tropical cyclogenesis abstractrecent numerical modeling and observational studies indicate the importance of vortical hot towers vhts in the transformation of a tropical disturbance to a tropical depression it has re

influence of equatorial waves on the genesis of super typhoon haiyan 2013 abstractthe influence of equatorial wave disturbances on the genesis of super typhoon haiyan 2013 is investigated through spectral composite and ensemble sensitivity analysis of various observational datasets in combination with predictions from an operational ensemble under the favorable large scale environmental conditions of the asian monsoon combined with the madden julian oscillation mjo the incipient haiyan develops from a cyclonic disturbance that originates from a train of westward propagating mixed rossby gravity mrg waves haiyan eventually develops in the monsoon trough region at the leading edge of the moist mjo phase that has strong low level convergence high moisture content and weak shear along with high sea surface temperature these favorable environmental conditions promote the intensification of deep moist convection that facilitates the development of the cyclonic disturbance from an mrg wave into a tropical depression which later intensifies rapidly into super typhoon ha

a vortical hot tower route to tropical cyclogenesis abstract a nonhydrostatic cloud model is used to examine the thermomechanics of tropical cyclogenesis under realistic meteorological conditions observations motivate the focus on the problem of how a midtropospheric cyclonic vortex a frequent by product of mesoscale convective systems during summertime conditions over tropical oceans may be transformed into a surface concentrated warm core tropical depression as a first step the vortex transformation is studied in the absence of vertical wind shear or zonal flow within the cyclonic vorticity rich environment of the mesoscale convective vortex mcv embryo the simulations demonstrate that small scale cumulonimbus towers possessing intense cyclonic vorticity in their cores vortical hot towers vhts emerge as the preferred coherent structures the vhts acquire their vertical vorticity through a combination of tilting of mcv horizontal vorticity and stretching of mcv and vht generated vertical vorticity horizontally localized and exhibiting conve

the formation of hurricane humberto 2001 the importance of extra tropical precursors the authors examine the formation of hurricane humberto 2001 in the atlantic basin precursor disturbances originating in the extratropics appear critical for inducing tropical cyclogenesis one precursor near the tropopause arose during the development of hurricane erin on 7 september and could be tracked continuously for 12 days until 1200 utc 19 september a fully explicit numerical simulation with the psu ncar mesoscale model produces a generally realistic evolution of the developing storm during a 4 day period beginning 0000 utc 19 september diagnostics of the simulations reveal that moderate vertical shear was crucial for organizing convection and this shear was enhanced on the periphery of an upper level vortex within a lower to mid tropospheric baroclinic zone downdraughts and evaporative cooling produced a rearward propagating bore that organized new convection in a notably moistened environment with small cape vorticity generation maximized near 1 km above mean sea level and the vortex built upward with time this evolution contrasts markedly with downward development conceptual models of tropical cyclogenesis and points to the crucial need for observations in the lower troposphere before depression formation convective scale dynamics were governed by intense convective cores which produced most of the diabatic heating and lower tropospheric vertical vorticity they were constrained by vertical shear to populate the downshear left quadrant of the vortex and therefore their collective behaviour was organized despite being quasi random within the favoured region ultimately the shear that helped organize the convection in the developing depression hampered humberto s subsequent intensification copyright 2006 royal meteorological society

gradient balance in tropical cyclones abstract analysis of a large inventory of in situ observations from research aircraft shows that the gradient wind approximates the axisymmetric swirling flow in the free atmosphere within 150 km of the centers of atlantic hurricanes and tropical storms in the middle and lower troposphere the rms difference between the azimuthal cream swirling and gradient winds is typically lt 1 5 m s 1 with zero bias this balance prevails only for the azimuthal mean not locally nor is balance to be expected in either the surface friction layer or the upper tropospheric outflow layer where the radial flow is comparable with the swirling flow it is theoretically possible that axisymmetric supergradient flow may occur in response to rapid radial acceleration where the radial flow slows in the friction layer beneath the eyewall or where it converges into intense diabatically forced updrafts nevertheless the observations in the free lower and midtroposphere show that systematic departures of the azimuthal mean vorte

three dimensional kinematic and microphysical evolution of florida cumulonimbus part iii vertical mass transport mass divergence and synthesis abstract a statistical technique is employed to examine the evolving properties of the ensemble small scale variability of high resolution radar data collected in a multicellular florida thunderstorm this paper examines vertical mass transport and mass divergence and synthesizes these observations with results from the first two parts of the study into a self consistent conceptual model that describes the convective to stratiform transition of the storm vertical mass transport distributions indicate that the more numerous weak and moderate strength upward and downward velocities not the few strongest accomplished most of the vertical mass transport in the storm hence most of the mass of precipitation is condensed outside the areas of intense upward motion these data thus suggest a change in the way we think about convection although the few regions of strongest vertical motion play a part in the overall storm evolution by dispersing particles throughout the depth of the storm it is the more preva

mesoscale observations of the genesis of hurricane dolly 1996 abstract recent numerical studies of tropical cyclone genesis suggest a new paradigm for how the surface vortex is established based on a highly nonaxisymmetric mechanism involving the interaction of low level cyclonic circulations generated by deep cumulonimbus convection a reexamination of mesoscale observations during the genesis of hurricane guillermo 1991 confirms the presence of multiple cyclonic circulations more recently airborne doppler radar wind observations during the genesis of atlantic hurricane dolly 1996 also reveal multiple lower to middle tropospheric mesoscale cyclonic circulations during sequential 15 20 min compositing periods a particularly well organized but initially weak mean tangential wind of 7 m s 1 low level cyclonic vortex embedded within the pre dolly tropical disturbance is observed coincident with deep vertically penetrating cumulonimbus convection the earliest observations of this vortex show the peak circulation near 2 km height with a mean diameter of 30 4

prediction and diagnosis of tropical cyclone formation in an nwp system part i the critical role of vortex enhancement in deep convection this is the first of a three part investigation into tropical cyclone tc genesis in the australian bureau of meteorology s tropical cyclone limited area prediction system tc laps an operational numerical weather prediction nwp forecast model the primary tc laps vortex enhancement mechanism is presented in part i the entire genesis process is illustrated in part ii using a single tc laps simulation and in part iii a number of simulations are presented exploring the sensitivity and variability of genesis forecasts in tc laps the primary vortex enhancement mechanism in tc laps is found to be convergence stretching and vertical advection of absolute vorticity in deep intense updrafts which result in deep vortex cores of 60 100 km in diameter the minimum resolvable scale is limited by the 0 15 horizontal grid spacing on the basis of the results presented it is hypothesized that updrafts of this scale adequately represent mean vertical motions in real tc genesis convective regions and perhaps that explicitly resolving the individual convective processes may not be necessary for qualitative tc genesis forecasts although observations of sufficient spatial and temporal resolution do not currently exist to support or refute this proposition relatively large scale 30 km and greater lower to midlevel tropospheric convergent regions have been observed in tropical oceanic environments during the global atmospheric research programme garp atlantic tropical experiment gate the equatorial mesoscale experiment emex and the tropical ocean global atmosphere coupled ocean atmosphere response experiment toga coare and regions of extreme convection of the order of 50 km are often remotely observed in tc genesis environments these vortex cores are fundamental for genesis in tc laps they interact to form larger cores and provide net heating that drives the system scale secondary circulation which enhances vorticity on the system scale akin to the classical eliassen problem of a balanced vortex driven by heat sources these secondary vortex enhancement mechanisms are documented in part ii in some recent tc genesis theories featured in the literature vortex enhancement in deep convective regions of mesoscale convective systems mcss has largely been ignored instead they focus on the stratiform regions while it is recognized that vortex enhancement through midlevel convergence into the stratiform precipitation deck can greatly enhance midtropospheric cyclonic vorticity it is suggested here that this mechanism only increases the potential for genesis whereas vortex enhancement through low to midlevel convergence into deep convective regions is necessary for genesis

evolution of multiscale vortices in the development of hurricane dolly 2008 abstract as a follow up to a previously published article on the initial development and genesis of hurricane dolly 2008 this study further examines the evolution of and interactions among multiscale vortices ranging from the system scale main vortex l 150 km to the intermediate scale cloud clusters 50 km l 150 km and individual vorticity rich convective cells l 50 km it is found that there are apparent self similarities among these vortices at different scales each of which may undergo several cycles of alternating accumulation and release of convective available potential energy enhanced surface fluxes below individual cyclonic vortices at each scale contribute to the sustainment and reinvigoration of moist convection that in turn contributes to the maintenance and upscale growth of these vortices spectral analysis of horizontal divergence and relative vorticity further suggests that the cloud cluster scale and system scale vortices are predominantly balanced while the individual

initial development and genesis of hurricane dolly 2008 abstract based on a successful cloud resolving simulation with the weather research and forecasting model this study examines key processes that led to the early development of hurricane dolly 2008 the initial development of dolly consisted of three stages i an initial burst of convection ii stratiform development dry intrusion and thermodynamic recovery and iii reinvigoration of moist convection and rapid intensification advanced diagnosis of the simulation including the use of vorticity budget analysis contour frequency analysis diagrams and two dimensional spectral decomposition and filtering suggests that the genesis of dolly is essentially a bottom up process the enhancement of the low level vorticity is mainly ascribed to the stretching effect which converges the ambient vorticity through stretching enhanced by moist convection in the rapid intensification stage smaller scale positive vorticity anomalies resulting from moist convection are wrapped into the storm center area u

prediction and diagnosis of tropical cyclone formation in an nwp system part ii a diagnosis of tropical cyclone chris formation this is the second of a three part investigation into tropical cyclone tc genesis in the australian bureau of meteorology s tropical cyclone limited area prediction system tc laps the primary tc laps vortex enhancement mechanism convergence stretching and vertical advection of absolute vorticity in convective updraft regions was presented in part i in this paper part ii results from a numerical simulation of tc chris western australia february 2002 are used to illustrate the primary and two secondary vortex enhancement mechanisms that led to tc genesis in part iii a number of simulations are presented exploring the sensitivity and variability of genesis forecasts in tc laps during the first 18 h of the simulation a mature vortex of tc intensity developed in a monsoon low from a relatively benign initial state deep upright vortex cores developed from convergence stretching and vertical advection of absolute vorticity within the updrafts of intense bursts of cumulus convection individual convective bursts lasted for 6 12 h with a new burst developing as the previous one weakened the modeled bursts appear as single updrafts and represent the mean vertical motion in convective regions because the 0 15 grid spacing imposes a minimum updraft scale of about 60 km this relatively large scale may be unrealistic in the earlier genesis period when multiple smaller scale shorter lived convective regions are often observed but observational evidence suggests that such scales can be expected later in the process the large scale may limit the convection to only one or two active bursts at a time and may have contributed to a more rapid model intensification than that observed the monsoon low was tilted to the northwest with convection initiating about 100 200 km west of the low level center the convective bursts and associated upright potential vorticity pv anomalies were advected cyclonically around the low weakening as they passed to the north of the circulation center leaving remnant cyclonic pv anomalies strong convergence into the updrafts led to rapid ingestion of nearby cyclonic pv anomalies including remnant pv cores from decaying convective bursts thus convective intensity rather than the initial vortex size and intensity determined dominance in vortex interactions this scavenging of pv by the active convective region termed diabatic upscale vortex cascade ensured that pv cores grew successively and contributed to the construction of an upright central monolithic pv core the system scale intensification ssi process active on the broader scale 300 500 km radius also contributed latent heating slightly dominated adiabatic cooling within the bursts which enhanced the system scale secondary circulation convergence of low to midlevel tropospheric absolute vorticity by this enhanced circulation intensified the system scale vortex the diabatic upscale vortex cascade and ssi are secondary processes dependent on the locally enhanced vorticity and heat respectively generated by the primary mechanism

vertical motion characteristics of tropical cyclones determined with airborne doppler radial velocities abstract vertical motions in seven atlantic hurricanes are determined from data recorded by doppler radars on research aircraft the database consists of doppler velocities and reflectivities from vertically pointing radar rays collected along radial flight legs through the hurricane centers the vertical motions are estimated throughout the depth of the troposphere from the doppler velocities and bulk estimates of particle fallspeeds portions of the flight tracks are subjectively divided into eyewall rainband stratiform and other regions characteristics of the vertical velocity and radar structure are described as a function of altitude for the entire dataset and each of the four regions in all of the regions more than 70 of the vertical velocities range from 2 to 2 m s 1 the broadest distribution of vertical motion is in the eyewall region where 5 of the vertical motions are 5 m s 1 averaged over the entire dataset the mean vertical velocity is upward at all altitudes mean downward mot

tracking gravity waves in baroclinic jet front systems abstract using a two dimensional fourier decomposition and a four dimensional ray tracing technique the propagating characteristics and source mechanisms of mesoscale gravity waves simulated in idealized baroclinic jet front systems are investigated the fourier decomposition successfully separates the simulated gravity waves from a complex background flow in the troposphere four groups of gravity waves in the lower stratosphere are identified from the spectral decomposition one is a northward propagating short scale wave packet with horizontal wavelength of 150 km and another is a northeastward propagating medium scale wave packet with horizontal wavelength of 350 km both of these are most pronounced in the exit region of the upper tropospheric jet a third group exists in the deep trough region above and nearly perpendicular to the jet and a fourth group far to the south of the jet right above the surface cold front both of which are short scale waves and have a horizontal wavelength of 100

what is the key feature of convection leading up to tropical cyclone formation abstractinfrared brightness temperature data are used to investigate convective evolution during tropical cyclone tc formation in a quasi lagrangian framework more than 150 named atlantic storms

an air sea interaction theory for tropical cyclones part ii evolutionary study using a nonhydrostatic axisymmetric numerical model abstract in part i of this study an analytical model for a steady state tropical cyclone is constructed on the assumption that boundary layer air parcels are conditionally neutral to displacements along the angular momentum surfaces of the hurricane vortex the reversible thermodynamics implied by this assumption allows the mature storm to be thought of as a simple carnot engine acquiring heat at the high temperature ocean surface and losing heat near the low temperature tropopause although the oceanic heat source is universally recognized as the sine qua non for the mature hurricane there is also wide acceptance of conditional instability of the second kind cisk which makes no specific reference to surface heat fluxes as the formative mechanism this ambivalence is seen in that all numerical simulation studies find it essential to have transfer from the ocean surface yet all start from a conditionally unstable atmosphere the hypothesis put forward in part i based on the steady state theory is t